WO2008019141A1

WO2008019141A1 - Selectable energy storage partitioned capacitor for defibrillation and method for pulse generation

Info

Publication number: WO2008019141A1
Application number: PCT/US2007/017537
Authority: WO
Inventors: Gregory J. Sherwood; Joesph M. Bocek
Original assignee: Cardiac Pacemakers, Inc.
Priority date: 2006-08-03
Filing date: 2007-08-02
Publication date: 2008-02-14

Abstract

One embodiment of the present subject matter includes a method for pulse generation in an implantable device, comprising measuring an impedance between a first electrode and a second electrode and delivering a pulse based on a pulse energy level and a pulse duration limit, comprising generating a pulse duration as a function of the pulse energy level and the impedance and selecting a capacitance value from a plurality of capacitances in a partitioned capacitor bank to deliver a pulse at the pulse energy level and wherein the pulse duration is less than the pulse duration limit.

Description

SELECTABLE ENERGY STORAGE PARTITIONED CAPACITOR FOR DEFIBRILLATION AND METHOD FOR PULSE GENERATION

CLAIM OF PRIORITY Benefit of priority is hereby claimed to U.S. Patent Application Serial

Number 11/462,281, U.S. Patent Application Serial Number 11/462,295, and U.S. Patent Application Serial Number 11/462,301, all filed on August 3, 2006, which are herein incorporated by reference.

CROSS REFERENCE TO RELATED APPLICATIONS

The following commonly assigned U.S. Patent is related to the present application and is incorporated herein by reference in its entirety: "METHOD AND APPARATUS FOR HIGH VOLTAGE ALUMINUM CAPACITOR DESIGN," U.S. Patent No. 7,224,575, filed on July 15, 2005.

TECHNICAL FIELD

This disclosure relates generally to electrical energy storage, and more particularly to method and apparatus for selectable energy storage partitioned capacitor.

BACKGROUND

Cardiac rhythm management devices use relatively large capacitors to provide pulses of electrical energy. Specifically, cardiac rhythm management devices provide large pulses for therapies including defibrillation therapies. These capacitors are capable of delivering variable energy by varying their voltage. These capacitors are not able to deliver varying energy levels at a constant voltage. This inability presents several problems.

One problem is that in some instances, a load which receives a defibrillation pulse is not understood until after a device is connected to that load. Various application requirements specify that a certain amount of energy be delivered at a particular voltage and within a fixed time limit. If the first connected device is not sized appropriately, the inability to alter the energy storage capability of the device requires that the device be swapped with a second device having an appropriately sized capacitor. This complicates procedures used to connect a device to a load. This also requires the manufacture and inventory of multiple devices, with some devices being redundant. A new design is needed to overcome these problems.

SUMMARY

The above-mentioned problems and others not expressly discussed herein are addressed by the present subject matter and will be understood by reading and studying this specification.

One embodiment of the present subject matter includes a method for pulse generation in an implantable device, comprising measuring an impedance between a first electrode and a second electrode and delivering a pulse based on a pulse energy level and a pulse duration limit, comprising generating a pulse duration limit as a function of the pulse energy level and the impedance and selecting a capacitance value from a plurality of capacitances in a partitioned capacitor bank to deliver a pulse at the pulse energy level and wherein the pulse duration is less than the pulse duration limit.

One embodiment of the present subject matter includes an impedance sensor adapted to deliver a signal, capacitor means for delivering a first defibrillation pulse of a first amount of energy, and a second defibrillation pulse at a second amount of energy, the first and second pulse being delivered at a common voltage and switch means for switching the capacitor means between a first mode for delivering the first pulse and a second mode for delivering the second pulse, the switching based on the signal of the impedance sensor.

Optional features within the scope of the present subject matter include devices configured to avoid capacitor discharge times longer than 0.020 ms. Some options include measuring a system impedance between 40 and 60 ohm. Some options include a first capacitor which can store three times the energy of the second capacitor. Some options include switches which include jumpers, semiconductor devices, and switches which are programmable using wireless communication. Options within the present scope include a capacitor adapted to deliver from around 5.3 joules per cubic centimeter of stack volume to about 6.3 joules per cubic centimeter of stack volume and a capacitor stack adapted to deliver from about 7.0 joules per cubic centimeter to about 8.5 joules per cubic centimeter. Some options include capacitors which can store 31 joules of energy, and some options include capacitors which can store 41 joules of energy. Additional options include a common cathode among two capacitors, two capacitors implanted in an implantable cardioverter defibrillator, and cases for capacitors which are sealed hermetically. Some options include a seal for a capacitor case which resists the flow of electrolyte. Some options include electronics, which can include power source control electronics for controlling what is connected to a first and second capacitor.

One embodiment of the present subject matter includes a capacitor case, a first capacitor stack disposed in the capacitor case and including at least a first anode layer and at least a first cathode layer, the first anode layer including a first anode connection member, a first feedthrough disposed through the capacitor case and connected to the first anode connection member, a second capacitor stacked onto the first capacitor in alignment, the second capacitor including at least a second anode layer and at least a second cathode layer, with a second anode connection member which is aligned with the first anode connection member along the direction of stacking, a second feedthrough disposed through the capacitor case and connected to the second anode layer and a single electrolyte disposed in the capacitor case, wherein the first and second cathode layers are electrically connected, and the first and second anode layers are electrically isolated.

Another embodiment within the scope of the present subject matter includes a capacitor case, a capacitor roll disposed in the capacitor case, the capacitor roll including at least a first cathode layer, at least a first anode layer, and at least a second anode layer, a first feedthrough disposed through the capacitor case and connected at least to the first anode layer, a second feedthrough disposed through the capacitor case and connected at least to the second anode layer, a single electrolyte disposed in the capacitor case and substantially filling interstices in the capacitor case, wherein the first and second anode layers are electrically isolated. One embodiment of the present subject matter includes a capacitor case, a first capacitor disposed in the case and including at least a first anodic electrode and at least a cathodic electrode, a second capacitor disposed in the case and including at least a second anodic electrode, a first feedthrough disposed through the case and connected to the first anodic electrode and a second feedthrough disposed through the case and connected to the second anodic electrode, wherein the first and second anodic electrodes are in electrical isolation and the first capacitor has a first capacitance which is approximately three times a second capacitance of the second capacitor. Options within the present scope include capacitors which are adapted to deliver to the first and second feedthrough from about 5.3 joules per cubic centimeter of stack volume to about 6.3 joules per cubic centimeter of stack volume. Options also include feedthroughs, some of which are sealed. Options include capacitors which can store 10 joules, and 31 joule capacitors are additionally covered by the present scope. Options include a cathodic case. Some options include a cathode shared between a first and second capacitor. Options include stacks of capacitor electrodes in alignment. Options include capacitor stacks which are partitioned with separator. Options include a first and second capacitor connected in parallel. Options additionally include a capacitor case which is sealed. Some of these options are hermetically sealed. Some options include a capacitor disposed I an implantable medical device, such as an implantable cardioverter defibrillator. Optional switches used with capacitors of the present subject matter include hard switches and semiconductor switches. Switches within the present scope are optionally controlled by electronics, which can be controlled wirelessly in some embodiments. Some options within the present scope connect capacitor electrodes with connection members.

Disclosed herein, among other things, is an apparatus for charging and discharging partitioned capacitors. One embodiment of the apparatus includes multiple capacitive elements and a switching circuit connected between the capacitive elements. According to various embodiments, the switching circuit is adapted to programmably connect a plurality of the capacitive elements to provide a desired defibrillation capacitance. The switching circuit is adapted to programmably connect a plurality of the capacitive elements to selectively charge connected elements for use in a defibrillator, according to various embodiments.

Another embodiment of the apparatus includes a first and second capacitor in a stack, the first and second capacitors including a plurality of substantially planar electrodes. The apparatus embodiment also includes a switching circuit connected between the first and second capacitors. The switching circuit has at least two states, and is adapted to provide a first defibrillation capacitance in a first state and a second defibrillation capacitance in a second state, according to various embodiments.

A further embodiment of the apparatus includes a first and second capacitor in a stack, the first and second capacitors including a plurality of substantially planar electrodes. The apparatus embodiment also includes a switching circuit connected between the first and second capacitors, hi this embodiment, the switching circuit includes a field effect transistor (FET) adapted to have a source connected to the first capacitor and a drain connected to the second capacitor, a bipolar junction transistor (BJT) adapted to have an emitter connected to the source of the FET and a collector connected to a gate of the FET, a first current source connected to the collector of the BJT₅ and a second current source connected to a base of the BJT. According to various embodiments, activating the first current source turns the FET on, connecting the first and second capacitors, and activating the second current source turns the FET off, isolating the first and second capacitors.

One aspect of this disclosure relates to a method for making an apparatus with a variable defibrillation capacitance. According to an embodiment of the method, a first and second capacitor are formed in a stack, the first and second capacitors including a plurality of substantially planar electrodes, and a switching circuit is connected between the first and second capacitors. The switching circuit includes a first and second state, and selecting the first state selects the first and second capacitor to provide a defibrillation capacitance. Selecting the second state selects the first capacitor to provide a defibrillation capacitance, according to various embodiments.

One aspect of this disclosure relates to a method for making an apparatus for charging partitioned capacitors. According to an embodiment of the method, a first and second capacitor are formed in a stack, the first and second capacitors including a plurality of substantially planar electrodes, and a switching circuit is connected between the first and second capacitors. The switching circuit includes a field effect transistor (FET) connected between the first and second capacitors, a bipolar junction transistor (BJT) connected between a gate and source of the FET, a first current source connected to the gate of the FET, and a second current source connected to a base of the BJT. Selectively activating the first current source turns the FET on, connecting the first and second capacitors, and selectively activating the second current source turns the FET off, isolating the first and second capacitors according to various embodiments.

One aspect of this disclosure relates to a method for combining or isolating multiple capacitors within a capacitor stack. An embodiment of the method includes forming a first and second capacitor in a stack, the first and second capacitors including a plurality of substantially planar electrodes. The method embodiment also includes selecting the first capacitor and the second capacitor by activating a first electrical source and selecting the first capacitor by activating a second electrical source. According to various embodiments, the first electrical source and the second electrical source include a current source.

This Summary is an overview of some of the teachings of the present application and not intended to be an exclusive or exhaustive treatment of the present subject matter. Further details about the present subject matter are found in the detailed description and appended claims. Other aspects will be apparent to persons skilled in the art upon reading and understanding the following detailed description and viewing the drawings that form a part thereof, each of which are not to be taken in a limiting sense. The scope of the present invention is defined by the appended claims and their legal equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic of a power source including a first and second capacitor subset, according to one embodiment of the present subject matter.

FIG. 2 shows a schematic side view of a power source including a capacitor subset stack, according to one embodiment of the present subject matter.

FIG. 3 A shows a schematic side view of a power source including a capacitor subset stack, according to one embodiment of the present subject matter. FIG. 3B is a perspective view of the stack of FIG. 3 A after the stack has been processed according to one embodiment of the present subject matter.

FIG. 4A illustrates a graph representing characteristics of a capacitor, according to various embodiments of the present subject matter. FIG. 4B illustrates a graph representing characteristics of a capacitor, according to various embodiments of the present subject matter.

FIG. 4C illustrates a graph representing characteristics of a capacitor, according to various embodiments of the present subject matter. FIG. 5 illustrates a process for manufacturing a foil with a partially etched area, according to one embodiment of the present subject matter.

FIG. 6 shows a circuit for charging and discharging one or more capacitor subsets of a multi-capacitor subset capacitor stack, according to one embodiment of the present subject matter. FIG. 7 shows various capacitor wave forms based on a 40 ohm load, according to various embodiments of the present subject matter.

FIG. 8 shows various capacitor wave forms based on a 50 ohm load, according to various embodiments of the present subject matter.

FIG. 9 shows various capacitor wave forms based on a 60 ohm load, according to various embodiments of the present subject matter.

FIG. 10 shows an implantable device, according to one embodiment of the present subject matter.

FIG. 1 IA shows a wound capacitor, according to one embodiment of the present subject matter. FIG. 1 IB shows a partially wound capacitor, according to one embodiment of the present subject matter.

FIG. 12 is an isometric view of a flat capacitor according to one embodiment of the present subject matter.

FIG. 13 is a top view of a capacitor stack according to one embodiment. FIG. 14 is a side schematic view of the capacitor stack of FIG. 35.

FIG. 15 is a side schematic view of a capacitor stack according to one embodiment.

FIG. 16 is a cross-sectional view of a capacitor stack constructed in accordance with one embodiment. FIG. 17 is an exploded view of an anode stack constructed in accordance with one embodiment.

FIG. 18 is an exploded view of a modified anode stack constructed in accordance with one embodiment. FIG. 19 is an exploded view of a mixed anode stack constructed in accordance with one embodiment.

FIG. 20 is a cross-sectional view of a capacitor stack constructed in accordance with one embodiment. FIG. 21 is a perspective view of a capacitor— battery assembly including two stacked U— shaped capacitors and a battery nested within the capacitors.

FIG. 22 is a front view of the FIG. 52 assembly without the battery.

FIG. 23 is a side view of the FIG. 52 assembly.

FIG. 24 is a top view of the FIG. 52 assembly. FIG. 25 is an isometric view of a flat capacitor in accord with one embodiment of the present subject matter.

FIG. 26 is an exploded isometric view of the flat capacitor of FIG. 58.

FIG. 27 is another exploded isometric view of the flat capacitor of FIG. 58. FIG. 28 is a cross-sectional view of the feedthrough assembly of FIG.

58.

FIG. 29 is an isometric view of an exemplary coupling member in accord with one embodiment of the present subject matter.

FIG. 30 is an isometric view of the exemplary feedthrough assembly of FIG. 58.

FIG. 31 is a side view of the exemplary feedthrough assembly of FIG. 58.

FIG. 32 is an isometric view of another exemplary coupling member in accord with one embodiment of the present subject matter. FIG. 33 is an isometric view of another exemplary coupling member in accord with one embodiment of the present subject matter.

FIG. 34 is an isometric view of another exemplary coupling member in accord with one embodiment of the present subject matter.

FIG. 35 is a side view of the feedthrough assembly of FIG. 58. FIG. 36 is an exploded isometric view of a flat capacitor according to one embodiment of the present subject matter.

FIG. 37 is a cross-sectional view of the feedthrough assembly of FIG. 67. FIG. 38 is a cross-sectional side view showing a feedthrough plug according to one embodiment.

FIG. 39 is an exploded view of a flat capacitor according to one embodiment of the present subject matter. FIG. 40 is an isometric view of the feedthrough assembly of FIG. 70.

FIG. 41 is a cross— section view of the feedthrough assembly of FIG. 70.

FIG. 42 is a cross-section view of another exemplary feedthrough assembly according to one embodiment of the present subject matter.

FIG. 43 is a cross— section view of another exemplary feedthrough assembly according to one embodiment of the present subject matter.

FIG. 44 is a flow-chart of a method for manufacturing an electrolytic capacitor according to one embodiment of the present subject matter.

FIG.45 is a flow-chart of a method for replacing a first capacitor with a second capacitor according to one embodiment of the present subject matter. FIG.46 is a flow-chart of a method for manufacturing an implantable defibrillator according to one embodiment of the present subject matter.

FIG. 47 is an exploded perspective view of a capacitor according to one embodiment of the present subject matter.

FIG. 48 is a cross sectional view of portions of the capacitive stack of FIG. 78.

FIG. 49 is a partial cross sectional view of a capacitor with a cathode conductor positioned between the cover and the case according to one embodiment.

FIG. 50 is a partial cross sectional view of a capacitor with the cathode conductor attached to the cover and the case according to one embodiment.

FIG. 51 is a partial cross sectional view of a capacitor with the cathode conductor welded to the cover and the case according to one embodiment.

FIG. 52 is a view of a flat capacitor foil with an attached round wire connector according to one embodiment. FIG. 53 is a perspective view of a flat capacitor showing round wire connectors for interconnecting anode and cathode plates.

FIG. 54 is a view of a capacitor with an expanded end of a terminal wire attached to a case according to one embodiment. FIG. 55 is a view of a terminal wire attached to a case according to one embodiment.

FIG. 56 is a view of a terminal wire attached to a case according to one embodiment.

DETAILED DESCRIPTION

The following detailed description of the present subject matter refers to subject matter in the accompanying drawings which show, by way of illustration, specific aspects and embodiments in which the present subject matter may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the present subject matter. References to "an", "one", or "various" embodiments in this disclosure are not necessarily to the same embodiment, and such references contemplate more than one embodiment. The following detailed description is demonstrative and not to be taken in a limiting sense. The scope of the present subject matter is defined by the appended claims, along with the full scope of legal equivalents to which such claims are entitled.

The present subject matter relates to capacitors. In various embodiments, the present subject matter includes one or more capacitors including a plurality of substantially planar electrodes. In various embodiments, these substantially planar electrodes are in a stack. In some embodiments, the stack is plate shaped and as such, defines a flat capacitor. Capacitors of the present subject matter include anodic elements and cathodic elements. The present subject matter additionally includes capacitors using electrolyte. FIG. 1 shows a schematic of a power source including a first 102 and second 104 capacitor subset, according to one embodiment of the present subject matter. The power source 101 includes a case 110. Positioned inside the case 110, in various embodiments, is a stack 122 of substantially planar capacitor electrodes. Some embodiments use foil shaped electrodes. In various embodiments, the stack 122 includes cathodes and anodes. In some embodiments, case 110 is manufactured from a conductive material, such as aluminum. Stainless steel, titanium, or combinations thereof are used in optional embodiments. These materials are not an exhaustive or exclusive list, as other materials work with the present subject matter. For example, in additional embodiments, the case is manufactured using a nonconductive material, such as ceramic or plastic. The first 102 and second 104 capacitor subset store charge independently, in various embodiments. hi various embodiments, the case 110 includes one or more case portions. hi various embodiments, the one or more case portions are connected to one another, hi various embodiments, connected case portions are also connected to a seal which seals the case portions to one another. In various embodiments, the seal is a hermetic seal. In various embodiments, a seal can include a cured resin, hi additional embodiments, a seal can include a weld. Some embodiments of the present subject matter include a cured resin which resists the flow of electrolyte. Some of these embodiments allow for the passage of gas molecules. Some embodiments of the present subject matter include a seal adapted to allow the passage of hydrogen atoms. Some of these embodiments include cured epoxy resin. Various embodiments dispose electrolyte in the case 110. hi some embodiments, the electrolyte is fluidic in use. Some embodiments includes an electrolyte which substantially files interstices in the case. hi various embodiments, power source 101 includes a first terminal 130 and a second terminal 132 for connecting capacitor stack 122 to an outside electrical component. In some embodiments where case 110 is conductive, first terminal 130 and second terminal 132 are feedthroughs sealed to the case and electrically insulated from the case 110. Some embodiments include epoxy seals. The capacitor incorporates additional connection structures and methods in additional embodiments. The present subject matter includes, but is not limited to, additional embodiments disclosed on pages 12-13, 59-60, 63-82 of related and commonly assigned Provisional U.S. Patent Application: "Method and Apparatus for Single High Voltage Aluminum Capacitor Design," Ser. No. 60/588,905, filed on July 16, 2004, incorporated herein by reference. hi various embodiments, electrodes of the stack 122 are connected to the case 110. For example, in some embodiments, cathodes 116A-N of the stack are connected to the case 110. Cathodes 116A-N can be connected with a single mechanical connection 140, or multiple mechanical connections, in various embodiments. In some embodiments including multiple cathode layers which are electrically isolated from one another, the cathodes are interconnected in the case 110.

In some embodiments, the cathodes 116A-N are not connected to the case, but are instead routed out of the case through a third terminal 134. In some embodiments, the third terminal 134 is a feedthrough sealed to case 110. In additional embodiments, the third terminal is electrically insulated from the case 110. Additional embodiments within the present subject matter connect one or more anode layers to the case 110, and route the cathodes outside of the case 110 using terminals. Capacitor stack 122 includes one or more cathode layers 116A-N, one or more separator layers 115A-N, and one or more anode layers 114A-N, in various embodiments. In some embodiments, these components are stacked sequentially from the top of a stack to the bottom of a stack. The illustrated embodiment shows anode layers 114A-N which overhang cathode layers 116A-N. It should be noted that this configuration is only one of the configurations possible within the scope of the present subject matter, and additional embodiments include configurations in which there is no overhang. Separator layers 115 A-N overhang electrodes in some embodiments of the present subject matter, and do not overhang electrodes in additional embodiments of the present subject matter. Additionally, in some embodiments, capacitor subcomponents are organized into capacitor elements 120A-N. An example element includes an anode layer, a first separator layer, a cathode layer, and a second separator layers, although elements including other subcomponent configurations are within the scope of the present subject matter. In various embodiments, stack 122 is formed in two steps, including a first step of stacking capacitor components into two or more elements 120A-N, and a second step of stacking elements 120A-N into a stack. Various embodiment of the present subject matter include, but are not limited to, configurations disclosed on pages 41-50 of related and commonly assigned copending Provisional U.S. Patent Publication: "Method and Apparatus for

Single High Voltage Aluminum Capacitor Design," Ser. No. 60/588,905, filed on July 16, 2004, incorporated herein by reference.

Various embodiments of the present subject matter include one or more cathode layers. In various embodiments, at least one of the cathode layers 116A- N is metallic. Some embodiments use aluminum, tantalum, hafnium, niobium, titanium, zirconium, or combinations of these metals. Some embodiments use an aluminum substrate coated in titanium. Some embodiments including a titanium coating have an additional oxide coating. In various embodiments, multiple cathode layers in a stack are interconnected.

Embodiments of the present subject matter includes a third anode layer in the stack, and including a fourth terminal. A fourth terminal, in various embodiments, is sealed to the case. Some embodiments include a feedthrough for routing the third anode through the case. A third anode may additionally be connected to anodes of the stack 122 with a switch, as disclosed herein. Other anodes and partitions, including partitions greater than three, are contemplated by the present subject matter.

Interconnected layers can be interconnected using a variety of methods and structures which include: welding the cathode layers to each other; welding the cathode layers to each other using a filler metal; and welding an interconnection member to each layer. The presently disclosed connections are not exhaustive or exclusive of the present subject matter; additional connections fall within the present scope.

Some embodiments including a titanium coated cathode material have a higher capacitance per unit area than traditional aluminum electrolytic capacitor cathodes. Traditional cathodes which are 98% aluminum purity or higher generally have capacitance per unit area of approximately 250 uF/cm² for 30 micron thick cathode, with an oxide breakdown voltage in the 1—3 volt range. However, a cathode as described above results in a capacitance per unit area which, in some embodiments, is as high as 1000 uF/cm² or more.

Advantageously, this provides a single cathode which services an anode without exceeding the oxide breakdown voltage. When using a traditional cathode to service several layers (2 or more) of anode, the cathode voltage may rise as high as 5 or more volts, which is usually greater than the breakdown voltage. When this occurs, the aluminum cathode begins to form oxide by a hydration process which extracts oxygen from the water present in the electrolyte. The reaction produces hydrogen as a byproduct which in turn has the effect of creating an internal pressure within the capacitor, in various embodiments. Embodiments having internal pressure can demonstrate an undesirable mechanical bulge in the layers of the capacitor stack, or in the case. As such, the titanium-coated cathode described above serves as a corrective mechanism for hydrogen generation.

Various capacitor stack embodiments use separator layers 115 A-N to electrically separate two layers. Separator layers 115A-N, in some embodiments, additionally serve as a carrier for an electrolyte. A separator layer 115A-N can include a single layer of kraft paper, or multiple layers of kraft paper, in various embodiments. In some embodiments, two layers of craft paper are used to isolate a first electrode from a second electrode. In some of these embodiments, each kraft paper layer is approximately 0.05 inches in thickness. In various embodiments, the electrolyte can be any electrolyte for an electrolytic capacitor, such as an ethylene-glycol base combined with polyphosphates, ammonium pentaborate, and/or an adipic acid solute.

Various embodiments of the present subject matter include one or more anode layers 114A-N. In various embodiments, anodes can include aluminum, tantalum, hafnium, niobium, titanium, zirconium, and combinations of these metals. Other compositions not listed herein expressly are also used as an anode.

In one embodiment, at least portions of a major surface of each anode is roughened and/or etched to increase its effective surface area. This option can increase the capacitive effect of the anode on a volumetric basis, in various embodiments. Various embodiments use tunnel-etched, core-etched, and/or perforated— core-etched structures. Various embodiments utilize other compositions. In various embodiments, at least one of anode layers 114A-N is a high formation voltage anode. In various embodiments, the anodes are medium and/or low formation variations. An anode layer 114A-N, in various embodiments, can include anode sublayers. In some embodiments, one anode layer is a multi-anode stack including three anode sublayers. In various embodiments, an anode layer can include one, two, three or more anode sublayers. Depending on which process is used to construct the anode, various surfaces are coated with a dielectric. For example, in embodiments where the anode layers are punched from a sheet, which has previously been coated with dielectric, only the surfaces which have not been sheared in the punching process are coated with dielectric. Variously, if the dielectric is formed after punching, in various embodiments, all surfaces are coated. In some embodiments, anodes are punched from a larger sheet to minimize handling defects due to handling during the manufacturing process. For example, if a larger sheet is used as a starting material from which a number of anode layers are punched, machines or operators can grasp areas of the starting material which is not intended to form the final anode. Generally, in embodiments where the entire anode is not covered with dielectric, the anode is aged to restore the dielectric.

Various embodiments include a capacitor stack adapted to deliver between 7.0 Joules/cubic centimeter and 8.5 Joules/cubic centimeter. Some embodiments are adapted to deliver about 7.7 Joules/cubic centimeter. In some embodiments, the anode has a capacitance of between approximately 0.70 and 0.85 microfarads per square centimeter when charged at approximately 550 volts. In various embodiments, these ranges are available at a voltage of between about 410 volts to about 610 volts. In various embodiments, the stack is disposed in a case, and linked with other components, a state which affects some of these values. For example, in one packaged embodiment, including a case and terminals, the energy density available ranges from about 5.3 joules per cubic centimeter of capacitor stack volume to about 6.3 joules per cubic centimeter of capacitor stack volume. Some embodiments are adapted to deliver about 5.8 joules. In various embodiments, these ranges are available at a voltage of between about 410 volts to about 610 volts.

In various embodiments, a first capacitor stack configuration includes nine cathode layers, twenty separator layers, and twenty-eight anode layers. One way to form such a combination would be to stack eight elements including three anode layers and one element including two anode layers. The number of layers, and the number of elements, is selectable by a capacitor stack design and manufacturing process to achieve a desired capacitor power and thickness, in various embodiments. In various embodiments, a second capacitor stack configuration includes nineteen cathode layers, forty separator layers, and fifty-eight anode layers. One way to form such a combination would be to stack eighteen first elements, with each first element including three anode layers, one cathode layer, and two separators, with a second element including two anode layers, one cathode layer, and with a third element including two separators, and two anode layers. The number of layers, and the number of elements, is selectable by a capacitor stack design and manufacturing process to achieve a desired capacitor power and thickness, in various embodiments. The configuration offered as an example should not be construed as limiting, as other configurations are possible depending on packaging and power needs of various applications.

In various embodiments of the present subject matter, a capacitor includes 8 anode layers. In additional embodiments, a capacitor includes 2 cathode layers. In some embodiments, a capacitor includes 20 anode layers. In some embodiments, a capacitor includes 7 cathode layers.

Various embodiments of the present subject matter define two capacitive capacitor subsets, including a first capacitor subset 102 and a second capacitor subset 104, by partitioning the capacitor stack 122 into a first partition P₁ and a second partition P₂. hi some embodiments of the present subject matter, the two capacitor subsets are defined by two groups of interconnected anode layers.

Interspersed among the two groups of interconnected anode layers are a group of interconnected cathode layers, in various embodiments. In various embodiments, the capacitor exhibits a first storage capacity in a first mode of operation, and a second storage capacity in a second mode of operation. The first mode of operation, and the second mode of operation, in various embodiments, are selected by opening and closing a switch 106. In some embodiments, the switch 106 is a pair of contacts which are connected mechanically. Some embodiments use solder or a jumper to interconnect the contacts. In additional embodiments, switch 106 is a semiconductor device which is controlled by software. In some embodiments, the software and the semiconductor are integrated into the capacitor 101, and the capacitor 101 is connected to electronics at terminals 111 and 112. hi additional embodiments, the terminals 130 and 132, as well as the terminal 136, are connected to additional electronics. In these embodiments, the switch 106 is integrated with those additional electronics. hi additional embodiments, switch 106 is a semiconductor device which is controlled by software, hi some embodiments, the software and the semiconductor are integrated into the capacitor 101, and the capacitor 101. is connected to electronics at terminals 111 and 112. hi additional embodiments, the terminals 130 and 132, as well as the terminal 136, are connected to additional electronics. In these embodiments, the switch 106 is integrated with those additional electronics.

As discussed herein, the first partition and the second partition can be of different capacitances. In various embodiments, the first partition has a first capacitance value. In various embodiments, the partition has a second capacitance value. In some embodiments, the first and second capacitance values are equivalent. In additional embodiments, the first and second capacitance values are not equivalent. In some embodiments, one partition can store more energy than another partition. In some embodiments of the present subject matter, a first partition is sized to store approximately three times the energy of a second partition. As discussed herein, in implantable device embodiments, such a ratio of energy storage is useful to allow the capacitor partitions to be selected such that a first therapy energy level is available, and a second therapy energy level is available. Having a selectable therapy energy level allows capacitor designers and operators to adapt the implantable medical device to the requirements of multiple situations. Such adaptability, in various embodiments, can reduce surgery time and can improve the range of helpful treatments that are available to a patient. In some examples within the present subject matter, a switchable capacitor is compatible with a range of patients exhibiting a range of implant site impedances. In various embodiments, a care provider implants a device into a patient. A sensor is used to establish impedance, in various embodiments. In some embodiments, the sensor is mounted to an implanted lead which extends from the device to a shock site, in various embodiments. A care provider, in various embodiments, measures impedance at the shock site. This impedance is patient specific and varies from patient to patient. In some embodiments, the impedance is between approximately 40 ohms and approximately 60 ohms.

A required pulse energy level is determined, in various embodiments, hi some embodiments, a standard base level is used. In additional embodiments, a care provider induces fibrillation, and then shocks the patient to determine a conversion threshold. In various embodiments, the energy required for conversion is established as a base energy value, and a generic value ^s added to that base value. For example, if 5 joules are required for conversion, various embodiments add 10 joules and shock the patient with a 15 joule pulse during life saving therapies.

Capacitors within the present scope deliver a therapeutic pulse to a patient which is truncated. In various embodiments, a capacitor operates at a tilt level. A tilt level is the level at which a certain percentage of voltage in the capacitor has dissipated. For example, a tilt level of 60% represents a capacitor circuit which is designed to discharge until the voltage at the capacitor is 40% of what it was before the capacitor began to discharge. In various embodiments, switching is used to truncate capacitor dissipation. Embodiments within the present scope use a tilt voltage of from about 60% to about 80%. Some embodiments use a tilt voltage which is 66%.

The pulse duration is the time required to deliver energy. In various embodiments, the pulse duration is a function of tilt setting. The pulse duration is based, in part, on the impedance at the implant site. In various embodiments, design specifications limit care providers to wave forms of certain lengths, for example. If a device which is implanted in the patient demonstrates a pulse duration which is over a specified time limit, the device must be switched with a device which can deliver the required amount of energy without violating the specified time limit. As such, a care provider would have to explant a device, and replace it with a new device. In some embodiments, a design specification requires wave forms of a particular duration in a first region of the world in which a device is sold, and wave forms of a second duration in a second region of the world in which a device is sold. Embodiments of the present subject matter are suited to provide therapies in the United States and in Europe through the adjustment of switch 106. Such adjustability, in various embodiments, provides for an improved range of therapies care providers can administer.

A single capacitor stack including two capacitive capacitor subsets has several benefits. One benefit is that two capacitor subsets can be manufactured efficiently using manufacturing techniques used for capacitor stacks having a single capacitive capacitor subset. These benefits include the ability to weld along a single axis during the interconnection of multiple layers. These benefits additionally include the ability to quickly assembly a stack of fragile layers using pick and place technology. The benefits also include a reduction in process complexity. By eliminating one housing, the capacitor 101 offers reduced complexity. Along these lines, capacitor 101 can take the place of two capacitors in a parts inventory database. These are just some of the benefits the present design exhibits.

FIG. 2 shows a schematic side view of a power source including a capacitor subset stack, according to one embodiment of the present subject matter. In various embodiments, a power source 201 includes a first capacitor subset 202 and a second capacitor subset 204. Although the capacitor subset embodiments pictured are substantially flat and planar, other capacitor subset shapers are possible. The capacitor subset embodiments include a stack 216 of electrodes in various embodiments. Some embodiments include foil shaped electrodes. The capacitor subsets 202, 204 are disposed in a capacitor case 202.

Li various embodiments, the capacitor case also houses a switch 206. Switch 206, in various embodiments, represents a pair of connection contacts inside the case 206 which are hardwired together during assembly, hi additional embodiments, jumpers are used. Some embodiments include jumper accessible outside of a sealed implantable device. In other embodiments, high-current switch devices are used. In some embodiments, relays controlled by circuitry outside of case 206 are used. In some embodiments, switch 206 is a semiconductor device. In some embodiments, switch 206 is controlled wirelessly. Some of these embodiments use a wireless programmer to control the switch

206. In additional embodiments, switch 206 is controlled by computer software and hardware disposed in case 206. Some embodiments used feedthrough terminals 210 and 212 to program computer software and hardware which controls switch 206. This list is not exhaustive or exclusive of the present subject matter. Other switch embodiments not expressly recited herein additionally fall within the present scope.

Extending from the capacitor case and connected to the capacitor subsets 202, 204 are feedthrough terminals, in various embodiments. For example, some embodiments include an anodic feedthrough terminal 212. Additional embodiments include a cathodic feedthrough terminal 210. In some embodiments, the cathode terminal 210 is connected to the case 202, which is connected to a cathode of the capacitor. In some embodiments, the cathode terminal 210 is connected directly to the cathode of the capacitor. It should be noted that embodiments discussed herein which include anodes and cathodes represent only a portion of the embodiments within the scope of the present subject matter. In additional embodiments, electrodes which are disclosed as being anodic are cathodic. Similarly, in additional embodiments, electrodes which are disclosed as being cathodic are anodic.

FIG. 3 A is a partial perspective view of a capacitor stack of one or more anodes and cathodes, according to one embodiment of the present subject matter. Various embodiments include a stack 342 of one or more alternating anode layers 302 and cathode layers 303. As shown in FIG. 3 A, connection members 306 and 307 are overlaying and underlying each other. In various embodiments connection members 306 and 307 have some commonly positioned portions relative to each other and some portions which are exclusively positioned relative to each other. The pictured embodiment is one embodiment in which an anode connection member and a cathode connection member are aligned with one another along the direction of stacking.

For instance, proximal sections 309 of anode layers 302 are exclusively positioned or located. This means that at least a portion of proximal sections 309 do not overlay or underlay a portion of cathode 303. Likewise, proximal sections 308 of cathode 303 are exclusive portions and include at least a portion not overlaying or underlaying a portion of anode layers 302. Conversely, distal sections 311 and 310 are commonly positioned and each includes at least a portion overlaying or underlying each another. Cut-out portions 315 and 314 are also commonly positioned. Cut-out 319 is commonly positioned with cutout 312 while cut-out 313 is commonly positioned with cut-out 318. In various stacked embodiments the edges of distal sections 311 and 310 form a surface 340. In some of these embodiments, surface 340 can generally be described as including a first portion 340A which fronts the proximal sections 309 of anode layers 302, a second portion 340B which fronts common cut- portions 315 and 314, and third portion 340C which fronts the proximal sections 308 of cathode layers 303.

In various embodiments, distal sections 311 and 310 of anode connection member 307 and cathode connection member 306 are fully overlaying one another. Fully overlaying means that there are generally no gaps along surface 340 of stack 342 when the anodes and cathodes are stacked. The fully overlayed structure of stack 342 provides a complete surface 340 which provides for ease of edge— welding or otherwise connecting connection members 307 and 306 together. Other embodiments leave one or more gaps in surface 340 when the anodes and cathodes are stacked. For instance, in some embodiments, one or more of distal sections 311 or 310 may not reach all the way across front surface 340.

After being stacked as discussed above, at least portions of connection members 307 and 306 are connected to each other. For instance, in one embodiment, portions of distal sections 311 and 310 are connected to each other. In one embodiment, distal sections 311 and 310 are edge-welded at least partially along surface 340. In one embodiment, distal sections 311 and 310 are only connected along portion 340A and 340C of surface 340. hi one embodiment, distal sections 311 and 310 are soldered along surface 340. In some embodiments, portions of distal sections 310 and 311 are staked, swaged, laser— welded, and/or connected by an electrically conductive adhesive. In other embodiments, portions of proximal sections 309 are connected to each other and/or portions of proximal sections 308 are connected to each other. In various embodiments, insulator 370 assists in electrically isolating a first edge weld and a second edge weld, hi some embodiments, the insulator is a piece of separator paper. Other embodiments, the insulator is another insulative material, hi embodiments, the first edge weld defines a first capacitor 372, and a second edge weld defines a second capacitor 374. Additionally, some embodiments use a single edge weld to interconnect all the cathode layers 303.

After being connected, portions of connection members 307 and 306 are removed or separated so that proximal sections 309 and 308 are electrically isolated from each other. In some embodiments, a single edge weld interconnects anode layers 302 of capacitor subset 372, and then the joined anode layers 302 are excised into two or more capacitor subsets, hi one embodiment, a laser cut divides interconnected anode layers 302 into two or more capacitor subsets. In alternate embodiments, the anode layers 302 are connected, and the cathode layers 303 are excised into two or more capacitor subsets.

FIG. 3B is a perspective view of the stack of FIG. 3 A after the stack has been processed according to one embodiment of the present subject matter. FIG. 3B shows stack 342 after portions of distal sections 311 and 310 have been removed from the stack, forming a separation 382 between anode connection members 307, which together comprise anode connection section 388, and cathode connection members 306, which together comprise cathode connection section 380. Separation 382 in the present embodiment electrically isolates section 388 from section 380. Proximal sections 308 are still coupled to each other as are proximal sections 309. In some embodiments, separation 382 is a thin slice. In some embodiments, separation 382 is a wide cut— out. In some embodiments, an electrically insulative material is inserted in separation 382. In various embodiments, separation 382 is formed by laser cutting, punching, and/or tool or machine cutting. Separator 370 isolates first capacitor subset 372 from second capacitor subset 374.

FIGS. 4A-4C illustrate a graph representing characteristics of various embodiments of a capacitor, according to the present subject matter. The teachings of the present subject matter include a process for producing a capacitor which exhibits the traits illustrated by the graph. Among the various properties demonstrated by the graph are practical limitations tied to various aspects of capacitor design. Overall, the graph is useful to illustrate aspects which aid in selection and development of improved capacitors. The graph includes a three dimensional curve representing energy delivered in joules, voltage in volts, and volume in cubic centimeters. Depending on which aspects of the graph are analyzed, various trends are apparent.

For example, FIG. 4A demonstrates embodiments in which a capacitor delivers improved energy in the range of about 465 V to about 565V. The graph illustrates both the relationship between voltage and energy delivered, and volume and energy delivered. From reading and understanding the graph, it is apparent that higher voltages enable higher energy delivered, and that a higher capacitor volume enables higher energy delivered. The particular shape of the curves, and the energy delivered, are, in part, functions of the surface shape of the capacitor. For example, embodiments including capacitors with increased surface area due to etching, which have a dielectric formed on the surface area without substantial reduction in the surface area, provide more energy per volumetric unit. Additionally, embodiments which have increased dielectric thickness enable higher voltages, which also result in higher available energy levels. The present subject matter reveals varying preferential ranges considering these criteria.

For example, one embodiment of the present subject matter is adapted to deliver an electrical pulse at a voltage of between approximately 490 volts and approximately 540 volts. One embodiment is adapted to deliver an electrical pulse at approximately 515 volts. And additional embodiment is adapted to deliver an electrical pulse at approximately 550 volts. In some embodiments, a compromise is necessary to achieve the preferred performance. For example, in embodiments where approximately 515 volts is chosen as the operating voltage, an electrolyte which is unable to withstand higher voltages is used, hi varying embodiments, an electrolyte which is unable to operate at the peak of the voltages curve evident in the graph is chosen because of technology limitations and cost limitations. However, it is to be understood that the present subject matter encompasses embodiments which operate at the voltages demonstrated by the graph, and the examples included in these teachings are provided solely for illustration, and are not exhaustive or exclusive.

Additionally, the present subject matter includes embodiment adapted to deliver from about 5.3 joules per cubic centimeter of capacitor stack volume to about 6.3 joules per cubic centimeter of capacitor stack volume. Also, the present subject matter teaches embodiments adapted to deliver from about 5.5 joules per cubic centimeter of capacitor stack volume to about 6.1 joules per cubic centimeter of capacitor stack volume. One embodiment is adapted to deliver about 5.8 joules per cubic centimeter of capacitor stack. FIG. 4B shows a top view of a graph representing various properties of one capacitor embodiment of the present subject matter. The graph illustrates, in part, the relationship between voltage and energy delivered.

FIG. 4C includes a view of the graph which demonstrates the relationship, in part, between volume and energy delivered. In varying embodiments, the graph teaches that volumetric energy density, measured in joules per volt, increases when volume is minimized for a required energy delivered. Thus, by reading and understanding the information provided by the graph, it is possible to produce a capacitor with an improved packaging density, including, in part, improved volumetric energy density.

FIG. 5 shows a process for making a foil with a partially etched area, according to various embodiments of the present subject matter. In varying embodiments, the process includes depositing a curable mask onto a foil 552. For example, in one embodiment, the mask is deposited on a foil using a computer controlled mask dispensing system. In one example, ink is deposited using an ink-jet process. Various embodiments cure the mask onto the foil 554. Examples of curable mask include ink, and photoresist. In varying embodiments, the curable mask is cured to the foil. For example, in one embodiment, ink is deposited on the foil, and then is baked to the foil in an oven. Baking, in some embodiments, exposes the curable mask to radiant heat energy, which can increase hardness or the curable mask, and which also can decrease the time needed for curing. In varying embodiments, the oven is adapted to cure the curable mask without affecting the foil otherwise.

In varying embodiments, the foil is etched 556, and the mask protects the foil from the etchant. hi various embodiments, etching includes core— etching the foil, tunnel— etching the foil, perforating the foil and combinations and permutations of these techniques. In some embodiments, perforations are formed using lasers, chemical etchants, or mechanical dies, for example. Some embodiments tunnel-etch the foil, other embodiments provide other known methods of providing a porous or etched foil. In some embodiments, a porous anode structure is constructed using other roughening or etching techniques.

Varying examples of the process then remove the mask 558. Removing the mask, in one embodiment, includes submerging the foil with mask in a solution adapted to dissolve the mask.

Some embodiments anodize the foil 560 to form a dielectric. In one embodiment, forming a dielectric layer comprises forming a layer OfAl₂Oa having a thickness in the range of 573 nm to 1200 nm on the anode foil (assuming a dielectric growth rate of 1.3 —1.5 nm/V). In one embodiment, the dielectric layer is formed on the anode before the capacitor stack is constructed. In one embodiment, forming the dielectric layer includes applying a current through the anode and raising the voltage to the rated formation voltage. In one embodiment, the formation voltage is 441 volts. In other embodiments, the forming voltage is 450, 500, 550, 600, and 600-800 volts, and other voltages ranging from approximately 441 to approximately 800 volts or greater. The current causes a dielectric Al₂O₃ to form on the surface of the foil. Once the formation voltage is reached, the capacitor is held at that voltage until a leakage current stabilizes at a pre— determined level. By monitoring the rising voltage and/or the leakage current, the oxide formation can be estimated. Once the preset voltage is reached, it plateaus, in which case a current drop ensues in order to balance the increasing resistance of oxide film growth. The process is complete when the current drops to a pre-specified value. Some embodiments combine etching and dielectric forming so that the etching and dielectric forming are done simultaneously. In one embodiment, method 550 results in an aluminum anode foil having a formation voltage between approximately 441 volts and approximately 600 volts. In various embodiment, this includes a foil having a formation voltage of approximately 441 , approximately 450, approximately 500, approximately 550, approximately 600, and approximately 600 volts to approximately 800 volts or greater. Varying embodiments form a dielectric at approximately 600 volts to approximately 760 volts. In one embodiment, a dielectric thickness sufficient to withstand between about 653 volts and about 720 volts develops during formation. Other embodiments withstand from about 667 volts to about 707 volts during formation. One example is able to withstand about 687 volts during formation.

Varied processes can be utilized to produce the aluminum foil of the present subject matter. For example, one process includes forming a hydrous oxide layer on an aluminum foil by immersing the foil in boiling deionized water. The aluminum foil is also subjected to electrochemical anodization in a bath containing an anodizing electrolyte composed of an aqueous solution of boric acid, a phosphate, and a reagent. Additionally, the anodizing electrolyte contains a phosphate. In various embodiments, the anodizing electrolyte is at a pH of approximately 4.0 to approximately 6.0. In some examples, the foil is passed through a bath containing a borax solution. Borax, in various embodiments, includes a hydrated sodium borate, Na₂B₄O₇* IOH2O, and is an ore of boron.

In varying embodiments, the foil is reanodized in the boric acid- phosphate electrolyte previously discussed. In various embodiments of the present subject matter, the process produces a stabilized foil suitable for oxide formation of up to approximately 760 volts.

In various embodiments, the anodizing electrolyte contains about 10 grams per liter to about 120 grams per liter of boric acid and approximately 2 to approximately 50 parts per million phosphate, preferably as phosphoric acid, and sufficient alkaline reagent to lower the resistivity to within approximately 1500 ohm-cm to approximately 3600 ohm-cm and increase the pH from about 4.0 to about 6.0 for best anodization efficiency and foil quality.

Ih some embodiments, the borax bath contains 0.001 to 0.05 moles/liter of borax. Because the anodizing electrolyte is acidic, in various embodiments, the borax bath is buffered with sodium carbonate to prevent lowering of the pH by dragout of the acidic electrolyte. Additionally, in various embodiments, the borax bath is buffered to lower its resistivity. In one example, the pH of the bath is from about 8.5 to about 9.5, and the temperature is at least approximately 80 degrees Celsius. In varying embodiments, the sodium concentration is approximately 0.005 to approximately 0.05M, preferably about 0.02 M. It should be noted that concentrations of less than approximately 0.005M are too dilute to control properly, and concentrations above approximately 0.05M increase the pH, resulting in a more reactive solution which degrades barrier layer oxide quality. In varying embodiments of the present subject matter, the presence of at least approximately 2 parts per million phosphate in the acidic anodizing electrolyte is critical. For example, this presence initiates stabilization of the foil so that solely hydrous oxide dissolves in the alkaline borax bath, without damage to the barrier layer dielectric oxide. In varying embodiments, this lowers ESR (equivalent series resistance) of the anodized foil.

Additionally, in various embodiments, when the foil is reanodized following the alkaline borax bath, the foil surface is alkaline and reacts electrochemically with the phosphate, which, in various embodiments, results in the incorporation of phosphate into the dielectric oxide. In varying examples, the alkaline foil surface includes an alkaline metal aluminate, and in one embodiment includes a sodium aluminate. It should be noted that the amount of allowable phosphate in the anodizing electrolyte, in various embodiments, is inversely proportional to the voltage at which the foil is being anodized. For example, in one embodiment, using greater than approximately 24 parts per million results in failure during oxide formation at around 650 volts. In embodiments where approximately 50 parts per million of phosphate is exceeded, the electrolyte scintillates at the foil interface, resulting in damaged, unstable foil. One benefit of the present subject matter is that an electrode is produced which can tolerate a high formation voltage without scintillation at the boundary layer of the foil. It should be noted that anodization temperature should be maintained from about 85 degrees Celsius to about 95 degrees Celsius, as variance outside of these values results in a the barrier layer oxide of lower quality, and foil corrosion. It should be noted that these teachings should not be understood to be exhaustive or exclusive, and other methods of forming a dielectric on a foil are within the scope of the present subject matter. Additionally, it should be noted that other examples anodize the foil while the mask is in place.

In addition, varying embodiments cut the anodized foil into shapes 562, and in some examples, the foil shapes are then assembled into a capacitor 564.

According to various embodiments, an apparatus is disclosed for providing a selective capacitance. The apparatus includes multiple capacitive elements and a switching circuit connected between the capacitive elements. According to various embodiments, the switching circuit is adapted to programmably connect a plurality of the capacitive elements to provide a desired defibrillation capacitance. The switching circuit is adapted to programmably connect a plurality of the capacitive elements to selectively charge connected elements for use in a defibrillator, according to various embodiments. The capacitive elements are housed in an implantable medical device, according to various embodiments.

In varying embodiments, the switching circuit is housed with the capacitive elements. In other embodiments, the switching circuit is housed separate from the capacitive elements. The switching circuit is housed adjacent to the capacitive elements, in further embodiments. The switching circuit can be accessible from outside the implantable medical device via wireless communication. Examples of wireless communication include inductive telemetry and radio frequency (RF) telemetry. According to various embodiments, the switching circuit is accessible from outside a human body in which the device is implanted via wireless communication. The apparatus may further include a flyback capacitor charger adapted to connect in parallel with the capacitive elements in an embodiment. According to one embodiment, the capacitive elements include a first and second capacitor in a stack. As discussed, the first and second capacitors can include a plurality of substantially planar electrodes, in varying embodiments.

Another embodiment of the apparatus includes a first and second capacitor in a stack, the first and second capacitors including a plurality of substantially planar electrodes. The apparatus embodiment also includes a switching circuit connected between the first and second capacitors. The switching circuit has at least two states, and is adapted to provide a first defibrillation capacitance in a first state and a second defibrillation capacitance in a second state, according to various embodiments. According to varying embodiments, the stack includes a common cathode which is shared by the first and second capacitor. The first defibrillation capacitance is equal to a capacitance of the first capacitor and the second defibrillation capacitance is equal to the sum of the capacitance of the first capacitor and a capacitance of the second capacitor, according to various embodiments.

FIG. 6 shows a circuit for charging and discharging one or more capacitor subsets of a multi-capacitor subset capacitor stack, according to one embodiment of the present subject matter. The circuit apparatus includes a first capacitor 616 and second capacitor 618 in a stack, the first and second capacitors including a plurality of substantially planar electrodes. The apparatus embodiment also includes a switching circuit connected between the first and second capacitors. In this embodiment, the switching circuit includes a field effect transistor (FET, 612) adapted to have a source connected to the first capacitor and a drain connected to the second capacitor, a bipolar junction transistor (BJT, 608) adapted to have an emitter connected to the source of the FET and a collector connected to a gate of the FET, a first current source 622 connected to the collector of the BJT, and a second current source 620 connected to a base of the BJT. According to various embodiments, activating the first current source 622 turns the FET on, connecting the first and second capacitors, and activating the second current source 620 turns the FET off, isolating the first and second capacitors. The FET 612 includes a 600 volt p-channel MOSFET, according to various embodiments. Other sizes and types of FETs may be used within the scope of this disclosure. The FET can have a relatively high 'on' resistance (such as 20 ohms, in an embodiment) because the FET conducts charging current. The BJT 608 includes a small, low voltage pnp bipolar junction transistor, such as part number 2N2907, according to an embodiment. Other sizes and types of BJTs may be used within the scope of this disclosure.

According to various embodiments, the stack includes a common cathode • which is shared by the first and second capacitor. The apparatus also includes a diode 614 adapted to connect the source of the FET to the drain of the FET. The diode 614 is adapted to conduct pulse current during discharge of the second capacitor, and according to various embodiments is adapted to have 600 volt capacity. Other sizes and types of diodes may be used within the scope of this disclosure. According to various embodiments, the apparatus also includes a second diode 610 adapted to connect the collector of the BJT to the emitter of the BJT. The second diode 610 may include a 10 volt zener diode. Other sizes and types of second diodes may be used within the scope of this disclosure. According to various embodiments, the apparatus includes a flyback capacitor charger 624 adapted to connect in parallel with the first capacitor.

A resistor 602 is adapted to connect the base of the BJT to the emitter of the BJT, according to various embodiments. The resistance value of the resistor 602 is selected to prevent the BJT from turning on due to off-state leakage current from the second current source. Thus the resistance value of resistor 602 should be less than or equal to the voltage drop across the base-emitter junction divided by the leakage current. In various embodiments, the resistor 602 is connected in parallel with a capacitor 604, which has a value of around 10 nF according to an embodiment. Node 628 is adapted to connect to the supply voltage (V ss) and node 626 is adapted to connect to a device output, such as a defibrillator bridge, according to various embodiments. In the depicted embodiment, both the first 616 and second 618 capacitors are connected to the output node 626 when the first current source 622 is activated during capacitor charging. In this embodiment, only the first capacitor is connected to the output node 626 when the second current source 620 is activated while high voltage is present on the first capacitor 616, which turns on BJT 608 and removes gate drive from FET 612, turning it off.

According to various embodiments the first and second capacitors are housed in an implantable medical device. The switching circuit may be housed with, adjacent to, or separate from the first and second capacitors in various embodiments. The switching circuit maybe accessible from outside the implantable medical device using a controller 630, according to an embodiment. In one embodiment, the switching circuit is accessible from outside a human body in which the device is implanted.

Another embodiment of the apparatus includes a first capacitor subset of a multi-capacitor subset capacitor stack, a second capacitor subset of a multi- capacitor subset capacitor stack and a switching circuit connected between the first and second capacitor subsets, the switching circuit adapted to charge and discharge the capacitor subsets. In this embodiment, the switching circuit includes a high voltage field effect transistor (FET) connected between the first and second capacitors, a low voltage bipolar junction transistor (BJT) connected between a gate and source of the FET, a first current source connected to the gate of the FET, and a second current source connected to a base of the BJT. According to various embodiments, activating the first current source turns the FET on, connecting the first and second capacitor subsets, and activating the second current source turns the FET off, isolating the first and second capacitor subsets.

According to various embodiments, the first capacitor subset is adapted to store approximately three times the energy of the second capacitor subset. According to one embodiment, the first capacitor subset stores around 31 Joules. The second capacitor subset stores around 10 Joules, in an embodiment.

One aspect of this disclosure relates to a method for making an apparatus with a variable defibrillation capacitance. According to an embodiment of the method, a first and second capacitor are formed in a stack, the first and second capacitors including a plurality of substantially planar electrodes, and a switching circuit is connected between the first and second capacitors. The switching circuit includes a first and second state, and selecting the first state selects the first and second capacitor to provide a defibrillation capacitance. Selecting the second state selects the first capacitor to provide a defibrillation capacitance, according to various embodiments. According to an embodiment, forming the first capacitor includes forming the first capacitor to store around 31 Joules. Forming the second capacitor includes forming the second capacitor to store around 10 Joules, according to one embodiment.

According to an embodiment, connecting a FET includes connecting a p- channel MOSFET and connecting a BJT includes connecting a PNP transistor, hi various embodiments, forming a first and second capacitor in a stack includes stacking into a stack a plurality of substantially planar capacitor electrodes, the stack include at least a first and second anode layer and a plurality of cathode layers, positioning the stack in the case, connecting the first anode layer to a first feedthrough disposed through the case, connecting the second anode layer to a second feedthrough disposed through the case, and connecting the plurality of cathode layers to the case. In various embodiments, connecting a switching circuit between the first and second capacitors includes connecting the first feedthrough, the second feedthrough, and the case to the switching circuit. The present subject matter includes embodiments which operate in various ways. Some applications in which the present subject matter is used include a design specification which requires that a defibrillator not deliver a therapeutic shock pulse which lasts longer than a pulse duration limit when operating at a specified tilt. The pulse duration limit in various embodiments is 20 milliseconds, and other times are used as well. Designing a pulse which does not exceed a pulse duration limit, but which delivers a required amount of energy, is straightforward if the impedance of the target is known. Unfortunately, the impedance of the target is not always known. In embodiments in which a device is implanted in a patient, target impedance is not known because of anatomical variations. As such, impedance of a target is not known until the therapeutic device is implanted. Embodiments using a device with an active housing additionally demonstrate this phenomenon. As such, care providers often must select a capacitor for an application after a device has been implanted, and site impedance has been measured. This can prolong surgery, because an initial impedance which is incorrect can require device removal and replacement during surgery. To address the problem of unknown impedance, the present subject matter includes embodiments which allow for selecting two or more different capacitances without device removal. By controlling the state of a switch, care providers can select between the first capacitance and a second capacitance. Varying capacitances are able to deliver required energy levels at different times. Embodiments within the scope of the present subject matter can switch two capacitors into a parallel relationship so that the operating voltage is the same, while capacitance and energy are increased. Pulse duration is adjusted accordingly. Various embodiments include more than two capacitors.

The following table corresponds to FIGS. 7-9. FIG. 7 shows various capacitor wave forms based on a 40 ohm load, according to various embodiments of the present subject matter. An example pulse duration limit 702 is shown for the 31 J 400μF waveform. FIG. 8 shows various capacitor wave forms based on a 50 ohm load, according to various embodiments of the present subject matter. An example pulse duration limit 802 is shown for the 3 IJ 400μF waveform. FIG. 9 shows various capacitor wave forms based on a 60 ohm load, according to various embodiments of the present subject matter. An example pulse duration limit 902 is shown for the 3 IJ 400μF waveform. Other impedances not listed herein expressly also fall within the present subject matter. Some embodiments of the present subject matter include a first capacitor subset having a capacitance of 78μF. In some of these embodiments, the energy storage of the first capacitor subset is 10 joules. Some of these embodiments include a second capacitor subset having a capacitance of 232μF. Some of these embodiments have an energy storage capacity of 31 joules. Accordingly, in some of these embodiments, the first and second capacitor subsets, when connected in parallel, have a capacitance of 310μF. Some of these embodiments have an energy storage ability of 41 joules. These examples are a capacitor subset of a larger group of variations possible within the scope of the present subject matter.

The table and FIGS. 7-9 show that a 400 μF capacitor charged to 393 volts violates the 0.20ms design requirement. The table also shows that a pair of capacitors switched in parallel can provide 3 IJ in a waveform which is shorter than the waveform for a 41 J capacitor. The table shows how the waveform lengths differ depending on impedance. Overall, the parallel configuration which allows an operator to use a first capacitor, a second capacitor or both the first capacitor and the second capacitor in parallel, allows for a wide range of applications with a single device including two capacitors.

Table 1 : Waveform Duration

Various embodiments of the present subject matter include a method which includes implanting an implantable device, including positioning at least a first lead proximal the heart. Various embodiments include measuring a system impedance at the first lead. Embodiments include comparing the discharge time of a first capacitor operating at a first tilt level to a threshold time. Some embodiment query if the discharge time is higher than a threshold time. Some embodiments include, when this condition is met, switching the first capacitor into parallel operation with a second capacitor of the implantable device. The switches shown and described herein can be implemented using software, hardware, and combinations of software and hardware. As such, the term "switch" is intended to encompass software implementations, hardware implementations, and software and hardware implementations.

In various embodiments, the methods provided above are implemented as a computer data signal embodied in a carrier wave or propagated signal, that represents a sequence of instructions which, when executed by a processor, cause the processor to perform the respective method. In various embodiments, methods provided above are implemented as a set of instructions contained on a computer-accessible medium capable of directing a processor to perform the respective method. In various embodiments, the medium is a magnetic medium, an electronic medium, or an optical medium.

Embodiment of Implantable Defibrillator FIG. 10 shows one of the many applications for capacitors incorporating one or more teachings of the present subject matter: an implantable heart monitor or apparatus 1000. As used herein, implantable heart monitor includes any implantable device for providing therapeutic stimulus to a heart muscle. Thus, for example, the term includes pacemakers, defibrillators, cardioverters, congestive heart failure devices, and combinations and permutations thereof. Heart monitor 1000 includes a lead system 1003, which after implantation electrically contact strategic portions of a patient's heart. Shown schematically are portions of monitor 1000 including a monitoring circuit 1002 for monitoring heart activity through one or more of the leads of lead system 1003, and a therapy circuit 1001 for delivering electrical energy through one or more of the leads to a heart. Monitor 1000 also includes an energy storage component, which includes a battery 1004 and incorporates at least one capacitor 1005 having one or more of the features of the capacitors described above.

In addition to implantable heart monitor and other cardiac rhythm management devices, one or more teachings of the present subject matter can be incorporated into cylindrical capacitors and/or capacitors used for photographic flash equipment. Teachings of the subject matter are pertinent to any application where high-energy, high-voltage, or space-efficient capacitors are desirable. Moreover, one or more teachings are applicable to batteries. FIG. 1 IA shows a rolled capacitor, according to one embodiment of the present subject matter. In one embodiment, capacitor 1140 includes a case 1100 for carrying, enclosing, or sealing a spirally wound aluminum electrolytic capacitor, as described below. First anode connection tab 1105, second anode connection tab 1135 and cathode connection tab 1110 provide electrical access to respective first anode, second anode and cathode terminals of capacitor 1140.

FIG. 1 IB shows a partially rolled capacitor, according to one embodiment of the present subject matter. First anode connection tab 1105 physically and electrically contacts portions of a first anode 1115. Ih various embodiments, the first anode 1115 includes multiple anode layers which are stacked and which are in contact with one another. In various embodiments, the first stack of anode layers includes anode layers which are electrically interconnected. In various embodiments, these layers are strip shaped. In some embodiments, the layers are ribbon shaped. Second anode 1130 connection tab 1135 physically and electrically contacts portions of a second anode 1130. In various embodiments, the second anode 1130 includes multiple anode layers which are stacked and which are in contact with one another. In various embodiments, the second stack of anode layers includes anode layers which are electrically interconnected. In various embodiments, these layers are strip shaped. In some embodiments, the layers are ribbon shaped. Cathode connection tab 1110 physically and electrically contacts portions of cathode 1120, in various embodiments. In various embodiments, cathode 1120 is strip shaped. In some embodiments, cathode 1120 is ribbon shaped. One or more separators 1125 isolate cathode 1120 from first anode 1115 and second anode 1130.

Incorporation by Reference

FIG. 12 shows a flat capacitor IOOA according to one embodiment of the present subject matter. Although capacitor IOOA is a D— shaped capacitor, in other embodiments, the capacitor is other desirable shapes, including, but not limited to rectangular, circular, oval, square, or other symmetrical or asymmetrical shape. Capacitor IOOA includes a case 101 A which contains a capacitor stack 102A. In one embodiment, case 101 A is manufactured from a conductive material, such as aluminum. In other embodiments, the case is manufactured using a nonconductive material, such as a ceramic or a plastic. One example uses a case 101 A which is formed from aluminum which is from about 0.010 inches thick to about 0.012 inches thick. In some examples, the case is electrically connected to an electrode of the capacitor, and one example uses the case as part of the cathode. For example, a conductive material is attached to the cathode and to the case, internal to the housing 101 A, in various embodiments.

Capacitor IOOA includes a first terminal 103A and a second terminal 104A for connecting capacitor stack 102 A to an outside electrical component, such as implantable medical device circuitry. In one embodiment, terminal 103A is a feedthrough terminal insulated from case 101A, while terminal 104A is directly connected to case 101 A. Alternatively, the capacitor incorporates other connection methods. For instance, in some embodiments, capacitor IOOA includes two feedthrough terminals.

In the present embodiment, capacitor stack 102 A includes capacitor modules or elements 105aA, 105bA, 105cA, . . ., 105nA.

FIG. 13 shows a planar view of a cathode stack 1800A according to one embodiment. The capacitor stack 1800A includes an anode layer 1801 A, a separator 1802 A, and a cathode layer 1803 A that are configured in a layered structure analogous to capacitor stack 24 described above. The bottom surface in the FIG. is the anode layer, and the top surface is the cathode layer with the paper separator interposed therebetween. The separator includes two paper separators impregnated with an electrolyte that conducts current between the anode and cathode layers.

Some cutting processes used to make anode and cathode foil layers can produce burrs on the foils that can result in a short circuit if a burr on an anode layer edge portion makes contact with an adjacent cathode layer or vice-versa. When the dimensions of the cathode and anode layers are the same so that the edges of each layer are aligned, a burr on a cathode layer edge portion can then contact a burr on an anode layer edge portion. Burrs on overlapping edge portions of the anode and cathode layers may then make contact and cause a short circuit by traversing only half of the thickness of the paper separator between the two layers.

Accordingly, in one embodiment, the capacitor stack is constructed with layers having edge portions that are offset from one another. In one embodiment, this is done by having a cathode layer with a different dimension than the anode layer so that portions of their edges are offset in the layered structure (i.e., either the anode layer or the cathode layer is smaller than the other). The anode and cathode layers may be of the same general shape, for example, but of different surface areas so that the perimeter of one layer is circumscribed by the perimeter of the other layer.

The capacitance of an electrolytic capacitor results from the charge separation between the electrolyte and the anode layer so that altering the surface area of the cathode layer does not appreciably affect the capacitance of the device. Such an arrangement is shown in Fig. 13 where the cathode layer 1S03A is of the same general shape as the anode layer 1801 A but with a smaller surface area such that the edge portions of the cathode layer are inwardly offset from the anode layer edges. In this structure, only an edge burr on the cathode layer that traverses the entire thickness of the paper separator can produce a short circuit. This is in contrast to the case where the edge portions of the two layers are aligned rather than being offset. Offsetting the edge portions results in a greater tolerance for edge burrs and allows a less constrained manufacturing process.

Fig. 14 shows a cross-sectional schematic of capacitor stack 1800A. The capacitor is made up of a plurality of capacitive elements that are stacked on one another with each capacitive element being a layered structure capacitor such as shown in Fig. 13. The anode layers 180 IA are stacked on cathode layers 1803 A in alternate fashion with paper separator 1802A interposed between each anode layer and each cathode layer.

Varying embodiments use assorted combinations of anodes and cathodes. For example, some embodiments of the capacitor stack include from about 16 planar cathode layers to about 20 substantially planar cathode layers, and from about 52 substantially planar anode layers to about 64 substantially planar anode layers, and one or more substantially planar separator layers. In one example, approximately 58 anode layers are used, and approximately 20 cathode layers are used, with each cathode layer separated from anode stack by approximately 40 separator layers. In this exemplary embodiment, two anode layers have been removed from the example to reduce the thickness of the capacitor stack. In varying examples, this is due to packaging considerations. The example also includes a stack which alternates between one cathode and three anode layers, also called an anode stack. The anode layers are not separated by a separator layer, in various embodiments, to save space.

Fig. 15 shows a capacitor stack 1900A according to one embodiment. Capacitor stack 1900A includes multiple porous anode layers 1901 A. The multiple layers result in a greater surface area exposed to the liquid electrolyte and a greater capacitance for each element. Three anode layers 190IaA- 190IcA are shown in the FIG. which are stacked together with a paper separator 1902 A and cathode layer 1903 A on each side of the stack. The liquid electrolyte flows through perforations in the anode layers to reach the oxide layers of each layer. The edge portions of each cathode layer 1903 A are inwardly offset from the edge portions of each overlying and underlying anode layer 1901 A.

In one embodiment, the offset structure described above can be incorporated into a cylindrical capacitor. For instance, the anode and cathode layers are cut from a sheet in a desired width and length. The cathode layer is made narrower than the anode layer so that the edges of the cathode layer are inwardly offset from the anode layer edges. The cylinder configuration is then produced by rolling the layers into concentric anode and cathode layers that are separated by electrolyte.

Offsetting of anode layer and cathode layer edge portions may be accomplished by using a variety of differently shaped and/or dimensioned cathode or anode layers.

In some embodiments, the cathode layer reduction ratio relative to the anode layer is limited. The electrical equivalent circuit of an electrolytic capacitor is the series connection of an anodic capacitance due to the charge separation that occurs between the anode layer and the electrolyte across the dielectric layer, an equivalent series resistance of the capacitor or ESR, and a cathodic capacitance due to the charge separation that occurs between the cathode layer and the electrolyte. When a capacitor is charged to its rated voltage, the voltage is divided and dropped across between the cathodic capacitance Cc and the anodic capacitance Ca. Since the charge stored on cathode layer Qc must equal the charge stored on the anode layer Qa, then: Qa = Qc CcVc = CaVa where Vc is the voltage dropped across the cathodic capacitance and Va is the voltage dropped across the anodic capacitance.

The voltage Vc is thus inversely proportional to the cathodic capacitance. The cathodic capacitance should be large enough so that only a small voltage drop occurs across it when a voltage is applied to the capacitor, with most of an applied voltage being dropped across the anodic capacitance. If the cathode layer is made small enough relative to the anode layer, the cathode layer's capacitance may be reduced to such an extent that when the capacitor's rated voltage is applied an overvoltage condition occurs at the cathode layer with the creation of oxide and evolution of hydrogen gas. Accordingly, in one embodiment the cathode layer is limited to the degree of decrease in surface area relative to the anode layer. In one embodiment, the cathode layer is kept to a size that keeps the overvoltage at tolerable levels when a rated voltage is applied to the capacitor. Such a minimum size for a cathode layer will vary, of course, with the capacitor's geometry and its rated operating voltage, but the size limit can easily be determined empirically.

In one embodiment, for example, flat capacitors used in implantable defibrillators is designed to operate at a rated voltage of 400 volts, and the ratio of the cathode layer surface area to the anode layer surface area is approximately 0.75 or greater. In some embodiments, the ratio is approximately 0.75 to approximately 0.93. In some embodiments, the ratio is approximately 0.93.

In some embodiments, capacitor stack 2024A includes a uniform level of anode foils in each anode stack 2200A. In other embodiments, the number of anode foils varies from stack to stack. For instance, FIG. 16 illustrates a cross-section of a capacitor stack

2160A according to one embodiment. One example of mixed anode stacks 2102 A is shown, which includes an anode stack 2100A and a modified anode stack 210 IA. The anode stack 2100A includes at least one conductive layer 2115A having a height 2146 A. The modified anode stack 2101 A includes a plurality of conductive layers 2118A such that the modified anode stack 2101 A includes at least one more conductive layer than included in the anode stack 2100A. The anode stack 2100A and the modified anode stack 2101 A differ in the quantity of conductive layers in each, hi addition, the anode stack 2100A and the modified anode stack 2101 A differ in the total surface area of each.

The anode stack 2100A, also shown in FIG. 17 includes a first conductive element 211OA, a second conductive element 2112A, and a third conductive element 2114 A, and an anode separator 2140A. hi one embodiment, as shown in FIG. 18, a modified anode stack 2101 A includes a first conductive element 211OA, a second conductive element 2112A, a third conductive element 2114A, and a fourth conductive element 2116 A, and an anode separator 2140 A, where the modified anode stack 2101 A includes at least one more conductive element than the anode stack 2100A. In another option, the modified anode stack 2101 A includes one or more less-conductive elements than the anode stack 2100A.

FIG. 19 illustrates another example of mixed anode stacks 2202A, which includes a first anode stack 2204A, a second anode stack 2206A, and a third anode stack 2208 A. The first anode stack 2204 A has a plurality of conductive layers 2215A including a first conductive element 2210A, a second conductive element 2212 A, and a third conductive element 2214 A. hi one option, the second anode stack 2206 A includes a first conductive element 2210A, a second conductive element 2212 A, a third conductive element 2214 A, and a fourth conductive element 2216 A. The third anode stack 2208 A includes a first conductive element 2210A, a second conductive element 2212 A, a third conductive element 2214A, a fourth conductive element 2216A, and a fifth conductive element 2218 A, where the second and third anode stacks 2206A, 2208 A include a different number of conductive elements than the first anode stack 2204A. In another option, the modified anode stack 2201 A includes one or more less conductive elements than the anode stack 2200A. In one embodiment, the first anode stack 2204A has a first surface area, and the second anode stack 2206A has a second surface area, and the first surface area is different than the second surface area, for example the second surface area is greater than the first surface area. In a further option, the first anode stack 2204A has a first surface area, the second anode stack 2206A has a second surface area, and the third anode stack 2208A has a third surface area. The third surface area is different than the first surface area and/or the second surface area, for example the third surface area is greater than the first surface area and/or the second surface area. The surface areas can be modified by modifying the surface of the conductive elements, for example, by etching. It should be noted that additional combinations of conductive layers and/or surface areas are contemplated and are considered within the scope of one or more embodiments of the present subject matter.

Referring to FIG. 20, the anode stack 2100A is coupled with the modified anode stack 2101 A, where there are a variety of ways to couple the modified anode stack 2101 A with the anode stack 2100A. In one example, the stack 2160A includes one or more connection members such as an edge clip 2150A and a modified edge clip 2170A, which interconnect the modified anode stack 2101 A with the anode stack 2100A. The modified edge clip 2170A, which is coupled with the modified anode stack 2101A, has a height 2142A that is extended for a slightly higher height of the modified anode stack 2101 A. The edge clip 2150A coupled with the anode stack 2100A has a height 2144A suitable for use with the anode stack 2100A. The edge clips 2150A, 2170A permit taller anode stacks to be reliably combined. The edge clips 2150A₅ 2170A are anodic and are optionally used to increase anodic surface area of the conductive layers 2115A as the edge clips 2150A, 2170A require little space within the capacitor stack 2160A. The composition of cells 2290A and modified cells 2292A as further discussed below, can be modified without requiring changes to other components in the capacitor stack 216OA resulting in greater design flexibility.

Referring again to FIG. 16, the capacitor stack 2160A includes at least one cell 290A, where each cell 2290A includes an anode stack 2100A, an anode separator 2140A, a cathode stack 2300A, and a cathode separator 2200A. In addition, the capacitor stack 2160A includes at least one modified cell 292 A, where each modified cell 292A includes a modified anode stack 2101 A, an anode separator 2140A, a cathode stack 2300A, and a cathode separator 2200A. In one option, the cathode stack 2300A and the cathode separator 2200A are substantially the same as included in the cell 2290A and the modified cell 2292 A, such that the difference in height between the anode stack 2100A and the modified anode stack 2101 A is due to the increase in height of the modified anode stack 210 IA resulting from the modified anode stack 2101 A having a greater number of conductive layers 2115 A than included in the anode stack 2100A. In another option, the modified anode stack 2101A of the modified cell 2292A has fewer conductive layers 2115A than the anode stack 2100A.

In one embodiment, a plurality of modified cells 2292 A is distributed throughout the capacitor stack 2160A in a manner to optimize use of existing cathodic area. In one example, the capacitor stack 2160A includes fifteen cells, where at otherwise would be every fifth cell 2290A, a modified cell 2292A is disposed instead. Since the modified anode stack 2101 A of the modified cell 2292A includes at least one more conductive layer than the anode stack 2100A, the resulting example of capacitor stack 2160A includes at least three additional conductive anode layers within the case 2OA, without a substantial increase in the height of the components therein. For instance, for the capacitor stack 216OA, instead of adding an additional anode stack 2100 A, which would have a height of three conductive layers 2115A (FIG. 17), and the height of an anode separator 2140A (FIG. 17), and the height of a separator 2200A, and the height of a cathode stack and an additional separator, only the height of the additional conductive layers 2115A in the modified anode stack 2101 A is added to the height of the capacitor stack 216OA.

In other embodiments the modified anode stack 2101 A contains one, two, three, four, five, six or more conductive layers 2115A than is included in each anode stack 2100A. Alternatively, more than one type of modified anode stack 2101 A is included with the capacitor stack 2160A. Referring again to FIG. 20, a stack 2160A is shown which includes cell

2290A, and modified cell 292A. An edge clip 2150A is adjacent the edge clip 2170A of an adjacent modified cell 292A. The edge clip 2150A is coupled to adjacent modified edge clip 2170A. For example, the edge clip 2150A is welded to the modified edge clip 217OA. Where a plurality of cells 2290A and modified cells 2292A are provided, a plurality of edge clips 215OA, 217OA are also provided. The plurality of edge clips 2150A, 2170A stack one on the other such that the bottom surface 2157 A of an edge clip 2150A or modified edge clip 2170A contacts the upper surface 2154A of an adjacent modified edge clip 2170, or edge clip 2150A. The stacked edge clips 2150A, 2170A provide a larger contact surface 2158 A increasing ease of attachment thereto. Each anode stack 2100A and modified anode stack 2101 A remains essentially flat and do not require the ductility required of other designs to niake an electrical connection. The stacked edge clips 2150A, 2170A provide for layer designs having higher stack composed of less ductile materials previously used, and further provide for interconnections in less space.

In one embodiment, an upper portion 2153 A of the edge clip 2150A or modified edge clip 2170A is positioned within a clearance area 2112A of the first conductive element 2110A. A side portion 2152A of the edge clip 2150A extends along the edges 2122A, 2132A of the second 2112A and third 2114A conductive elements, and extends along the edges of separators 2200A, and further along the edge of the anode separator 2140A of an adjacent modified anode stack 2101 A. The edge clip 2150A remains separate from the cathode stack 2300A. The side portion 2152 A of the modified edge clip 2170A extends along the edges 2122A, 2132 A, 2182 A of the second 2112 A, third 2114A, and fourth 2116A conductive elements. The side portion 2152 A also extends along the edges of separators 2200A, as well as along the edge of the anode separator 2140A of an adjacent anode stack 2100A or modified anode stack 2101 A. The edge clip 2170A remains separate from the cathode stack 2300A. In one embodiment, a method is also provided, the method involving aligning an anode stack, including aligning at least one conductive layer having a surface and an edge, and aligning a first separator between the anode stack and a modified anode stack. The method further includes aligning at least one modified anode stack with the anode stack, which includes aligning a plurality of conductive layers, wherein the plurality of conductive layers includes at least one more conductive layer than included in the anode stack and one of the plurality of conductive layers having a surface and an edge, and electrically coupling the anode stack with the modified anode stack.

Several variations for the method are as follows. The method further including welding an edge clip to the modified anode stack. In another embodiment, the method further includes aligning a first modified anode stack and a second modified anode stack, each having a plurality of conductive layers. In yet another embodiment, the method further includes stacking a first number of layers to form the first modified anode stack, and stacking a second number of layers to form the second modified anode stack, and the first number of layers is different than the second number of layers. In yet another embodiment, the method further includes aligning a second separator between the first modified anode stack and the second modified anode stack. Advantageously, the mixed-anode capacitor stacks described above allow for a reduction in the volume, thickness, and the mass of the stack without a reduction in the deliverable energy, which provides for a smaller overall device size. This results in increased patient comfort, and reduces tissue erosion surrounding the implantable device. In addition, reducing the size of the capacitor allows for other critical component sizes to be increased, for example, the battery, or for other components to be added. A further benefit is that anodic surface area is increased without requiring additional cathodic area to support the added anode conductive layers. This allows a boost in capacitance with a minimal increase in thickness of the capacitor. In empirical studies, capacitors that included the modified anode stack showed capacitance values of 186μF, 185μF, and 186μF, compared to standard devices without the modified anode stack which had capacitance values of 172μF, 172μF, and 173μF.

FIG. 21 shows a perspective view of a capacitor-battery assembly 3400A including two stacked U— shaped capacitors 3410A and 3420A and a battery 3430A nested within the capacitors. For sake of brevity, capacitor 3420A, which is of substantially identical size, shape, and structure as capacitor 3410A in this exemplary assembly, is not described separately. Capacitor 3410A includes legs 3412A and 3414A, respective middle (or intermediate) portions 3416A, and terminals 3418A. Legs 3412A and 3414A are parallel, and include respective curved surfaces 3412aA and 3414aA, and respective flat end surfaces 3412b and 3414b.

FIG. 22, a front view of assembly 3400A without battery 3430A, shows that curved surfaces 3412aA and 3414bA are generally congruent to each other and to respective curved profile 3502A and 3504A defined by capacitor modules 350OA. Further, it shows a housing 351OA (in phantom) having a curved or concave portions 3512A and 3514A generally congruent with or conformant to curved or convex surfaces 3412aA and 3414aA. (Some embodiments insulate and/or separate case 3606A from housing 3602A.) FIG. 23, a side view of assembly 3400A without battery 3430A, shows that the curved surfaces 3412aA and 3414bA are generally perpendicular to end surfaces 3412aA and 3412b A. Middle portion 3416 A is also shown as having a curved portion 3416aA which is congruent to a curved profile 3506A defined by capacitor modules 3500A and a curved portion of 3516A of monitor housing 3510A.

FIG. 24 is a top view of assembly 3400A, showing the general outline of capacitor modules 3500A. This FIG. also shows that battery 3430A includes terminals 3432A. FIG. 25 shows a flat capacitor 4100A in accord with one embodiment of the present subject matter. Capacitor 4100A includes one or more of the features of capacitor IOOA of FIG. 12. Thus the present discussion will omit some details which are referred to above regarding FIG. 12. Capacitor 4100A includes a case 4101 A, a feedthrough assembly 4103A, a terminal 4104A, and a sealing member 4105 A.

Case 4101 A includes a feedthrough hole 4107A which is drilled, molded, or punched in a portion of a wall of case 4101A. Feedthrough hole 4107A is in part defined by an edge 4107aA which outlines the feedthrough hole within case 4101 A. Feedthrough hole 4107A provides a passage for connecting feedthrough assembly 4103 A to circuitry outside of case 4101 A. In some embodiments, case 4101 A includes two or more feedthrough holes for providing a second or third feedthrough assembly.

Feedthrough assembly 4103 A and terminal 4104 A connect capacitor elements to outside circuitry. In the exemplary embodiment, feedthrough assembly 4103A extends through feedthrough hole 4107A and is insulated from case 4101A. Terminal 4104A is directly connected to case 4101 A. Alternatively, in some embodiments, the capacitor incorporates other connection methods, depending on other design factors. In various embodiments, two or more insulated feedthrough assemblies are employed. In one embodiment, sealing member 4105 A, such as an epoxy, is deposited around feedthrough hole 4107A and feedthrough assembly 4103A to insulate feedthrough assembly 4103 A from case 4101 A and to seal an electrolyte within the case. An exemplary epoxy is a two-part epoxy manufactured by Dexter Hysol. This includes a casting resin compound (manufacturer No. EE 4183), a casting compound (manufacturer No. EE 4215), and a hardener (manufacturer No. HD 3404). The exemplary two-part epoxy is mixed in a ratio of hardener = 0.055 * casting resin. The mixture is cured at 0.5 hours at 60 degrees Celsius or 1.5 hours at room temperature. Another epoxy is a UV cure epoxy such as manufactured by Dymax, Inc., which can be cured using an Acticure (manufactured by GenTec) ultraviolet curing system at 7 W/cm2 at a distance of 0.25" for approximately 10 seconds. In one embodiment, sealing member 4105 A is a plug, as will be discussed below.

In one embodiment, the sealing member provides a non-hermetic seal. In one embodiment, the sealing member includes an elastic plug which will be discussed in further detail below.

FIGS. 26 and 27 show exploded views of capacitor 4100A. Capacitor 4100A includes a capacitor stack 4202A mounted within an internal cavity 4212A. The exemplary capacitor stack 4202A includes a plurality of capacitor modules or elements 4205aA, 4205bA, 4205cA, . . ., 4205nA. Each of elements 4205aA-4205nA includes a cathode, an anode, and a separator between the cathode and the anode.

In one embodiment, each cathode of capacitor stack 4202 A is connected to the other cathodes and to conductive case 4101 A. Terminal 4104A is attached to case 4101 A to provide a cathode connection to outside circuitry. In some embodiments, the cathode is coupled to a feedthrough conductor extending through a feedthrough hole.

In one embodiment, each anode is connected to the other anodes of the capacitor. Attached to the anode of each capacitor element 4205aA-4205nA is a conductive tab or connection member 4201 A, as discussed above. In one embodiment, each connection member 420 IA includes an edge face 4215 A which is substantially perpendicular to the major surface of the anodes. Edge face 4215 A provides a conductive surface for connecting each capacitor element 4205aA— 4205nA to feedthrough assembly 4103 A. The anode connection members 4201 A are welded or crimped together and. are coupled to feedthrough assembly 4103 A for electrically connecting the anode to circuitry outside the case. In some embodiments, the cathode is coupled to a feedthrough assembly and the anode is connected to the case. In other embodiments, both the anode and the cathode are connected to feedthroughs. In one embodiment, connection members 4201 A are edge— welded to each other as discussed above. Edge— welding the connection members provides a flat connection surface 4216A, which includes one or more edge faces 4215A of connection members 420 IA. In some embodiments, connection members 4201 A are crimped, soldered, and/or connected by an electrically conductive adhesive.

In one embodiment, feedthrough assembly 4103 A includes two members, a feedthrough wire or conductor 4203A and a coupling member 4204A. Coupling member 4204A is attached to capacitor stack 4202A at connection surface 4216 A, and feedthrough conductor 4203 A is attached to coupling member 4204A. In one embodiment, coupling member 4204A partially extends through feedthrough hole 4107A.

Feedthrough conductor 4203 A is a conductive member which can include material such as nickel, gold plated nickel, platinum, aluminum, or other conductive metal. Feedthrough conductor 4203 A has a proximal end portion 4217A attached to coupling member 4204A and a distal end portion 4218A for attaching to circuitry outside the case, such as defibrillator or cardioverter circuitry. In one embodiment, feedthrough conductor 4203A has a diameter of approximately 0.016" (0.4064 mm). However, other embodiments have feedthrough conductors of different diameters and/or non-circular cross- sections.

FIG. 28 shows a cross-sectional side view of details of one embodiment of feedthrough assembly 4103 A and its connection to connection members 420 IA. As discussed above, in one embodiment, the edge faces 4215 A of each connection member 4201 A form a substantially flat connection surface 4216 A and coupling member 4204 A is directly attached to connection members 4201 A at surface 4216A.

In one embodiment, coupling member 4204A is a high— purity aluminum member which is able to withstand the high voltages generated within the capacitor case. In other embodiments it is made from another conductive material compatible with the capacitor stack. Coupling member 4204A includes a base 4404A and a holding tube 4407 A. On one side of base 4404A is a planar surface 4405 A for attaching to the planar surface 4216 A presented by edge- welded connection members 4201 A. FIG. 29 shows additional details of exemplary base 4404A. In the exemplary embodiment, base 4404A is substantially rectangular having a pair of opposing rounded or curved ends 4602A and 4604A.

Referring again to FIG. 28, in one embodiment, coupling member 4204A is situated so that surface 4405 A abuts connection member surface 4216 A.

Coupling member 4204A is laser welded using a butt— weld to surface 4216A of connection members 420 IA. Alternatively, coupling member 4204A is attached using other means. Butt— welding coupling member 4204A directly to connection members 4201 A provides an optimal electrical connection between capacitor stack 4202 A and the feedthrough assembly. Moreover, it also provides for a compact capacitor since very little, if any, space is wasted between capacitor stack 4202A and feedthrough assembly 4103 A. Also, since coupling member 4204A is directly attached to capacitor stack 4202A, it helps support feedthrough conductor 4203 A while a sealing member 4105 A, such as an epoxy, is applied to the feedthrough hole area.

Holding tube 4407A is located on the opposing side of base 4404A from surface 4405A. Tube 4407A is a cylindrical member having an outer diameter dimensioned to fit within feedthrough hole 4107 A. Tube 4407A has a mounting section such as mounting hole 4401A defined in part by an inner surface 4402A of holding tube 4406 A which is generally perpendicular to base surface 4405 A. Hole 440 IA is located down an axial portion of the tube.

Mounting section or hole 4401 A is for receiving proximal end portion 4217 A of feedthrough conductor 4203 A. The surface of feedthrough conductor 4203 A contacts inner surface 4402 A. In one embodiment, hole 4401 A is approximately 0.016" (0.4064 mm) in diameter. Alternatively, its diameter can conform with the size of conductor 4203 A so that feedthrough conductor 4203 A can matably fit within the hole. In one embodiment, coupling member 4204A has a height 204h of approximately 0.085" (2.519 mm). Other embodiments range from 0.050" to 0.100" or higher. Some embodiments provide a height of greater than 0.100".

FIGS. 30 and 31 show an attachment of feedthrough conductor 4203 A to coupling member 4204A according to one embodiment, hi the present embodiment, feedthrough conductor 4203 A and coupling member 4204A are connected at a crimp 4502A. Alternatively, they are welded, soldered, glued or interference fit together, as will be discussed below. Example crimp 4502A compresses inner surface 4402 A (see FIG. 28) of tube 4407 A into mechanical and electrical connection with the surface of portions of feedthrough conductor 4203 A. In one embodiment, a double crimp is employed. In some embodiments, a single crimp, double crimp, triple crimp or more are used.

In one embodiment, inner surface 4402A of coupling member 4204A is a curved surface, defining an annular connection member. Crimp 4502A compresses and deforms opposing surfaces of annular inner surface 4402A to contact conductor 4203 A. In one embodiment, the opposing surfaces of inner surface 4402A are separated by a first distance prior to being crimped and separated by a second distance, smaller than the first distance, after being crimped.

FIG. 32 shows another exemplary coupling member 4700A. Member 4700A includes a base 4701 A and a holding tube 4702A. Base 4701 A is a circular— shaped base. In one embodiment, base 4701 A has a diameter of approximately 0.050" (1.27 mm). In one embodiment (not shown), the base is square shaped.

FIG. 33 shows another example of a coupling member 4800A. Member 4800A does not include a base. In one embodiment, hole 4401 A runs completely through holding tube 4802A. In one embodiment, one end of tube 4802 A has a connection surface and is attached to surface 4216A of connection members 4201 A. A second end of tube 4802 A receives feedthrough conductor 4203A.

FIG. 34 shows another example of a coupling member 4850A. Member 4850A does not include a base. In one embodiment, hole 4401 A runs only partially through a holding tube 4852 A. In one embodiment, one end of member 4850A has a connection surface and is attached to surface 4216A of connection members 4201 A. An end of tube 4802 A receives feedthrough conductor 4203 A. FIG. 35 shows a side view of feedthrough assembly 4103 A in which feedthrough conductor 4203 A is coupled to coupling member 4204A at one or more arc percussion welding areas, such as areas 4982aA and 4982bA. An exemplary arc percussion welding machine is manufactured by Morrow Tech Industries of Broomfield, Colorado. In this embodiment, the conductor 4203 A and coupling members are not crimped together. However, some embodiments include both welding and crimping.

FIG. 36 shows an exploded view of capacitor 4100A having a sealing member such as a plug 4106 A according to one embodiment of the present subject matter. Plug 4106A is insertable into feedthrough hole 4107 A of case 4101 A. In one embodiment, plug 4106A has an outer diameter which is larger than the diameter of feedthrough hole 4107 A, and the manufacturer inserts it within hole 4107 A in an interference fit. When plug 4106 A is located within feedthrough hole 4107 A, the plug seals feedthrough hole 4107A and electrically insulates feedthrough assembly 4103 A from case 4101 A. In some embodiments plug 4106 A includes one or more flanges, which will be discussed below.

FIG. 37 shows a cross-sectional view of plug 4106A assembled with capacitor case 4101 A. The present example show coupling member 4204 A attached to capacitor stack 4202A. However, in other embodiments plug 4106A can also be used in capacitors having other types of feedthrough assemblies. In one embodiment, plug 4106 A electrically insulates case 4101 A from coupling member 4204A. Coupling member 4204A has a first end 4115 A located in the interior of case 4101 A and coupled to capacitor stack 4202 A. Coupling member 4204A also includes a second end 411 IA located exterior to case 4101 A for connecting to circuitry, such as defibrillator, or other implantable medical device circuitry. In one embodiment, coupling member 4204A has a feedthrough terminal attached thereto.

In this embodiment, plug 4106 A is a double— flanged plug. Plug 4106 A includes a first flange 4108 A. First flange 4108 A includes a first surface 4108aA which faces the inner surface of case 4101 A. When the capacitor begins to become pressurized, pressure against a second surface 4108bA forces first surface 4108aA against the case. Thus, flange 4108 A creates a seal against the inner surface of case 4101 A.

In this embodiment, plug 4106A includes a second flange 4109 A. Flange 4109 A includes a surface which faces the outer surface of case 4101 A.

Plug 4106A also includes a plug portion 411OA which is located between and defined by first flange 4108A and second flange 4109 A. Portion 411OA has a smaller diameter than either flange 4108 A and/or 4109 A. Case edge 4107aA confronts plug 4106 A at portion 411OA. In this embodiment, portion 411OA has a normal, unstressed outer diameter approximately equal to the diameter of feedthrough hole 4107 A. hi some embodiments, the unstressed outer diameter is larger than the diameter of feedthrough hole 4107 A. In some embodiments, the unstressed outer diameter is smaller than hole 4107 A. As one example, in this embodiment flange 4108 A has a diameter of approximately 0.080 inches and portion 411OA has a diameter of approximately 0.060 inches.

Plug 4106 A also includes a central passage or hole 4102 A. In one embodiment, hole 4102 A is axially located through the center of plug 4106A and has an unstressed diameter 4102dA which is smaller than or equal to a diameter 4103dA of a portion of feedthrough member 4103 A which is mounted within hole 4102 A. In various embodiments, diameter 4102dA may range from approximately 0.015 inches to approximately 0.033 inches. In other embodiments, diameter 4102dA is smaller than 0.015 inches, hi some embodiments it is greater than 0.033 inches. Other embodiments vary the hole size depending on the size of the feedthrough conductor used. In some embodiments, when a feedthrough member such as coupling member 4204A is inserted through hole 4102 A, an interference fit seal is developed between the feedthrough member and the plug. In other embodiments, hydrogen gas can escape along the feedthrough member/plug 4106A border. In one embodiment, plug 4106A is made from a compressible, elastic material such as rubber, plastic, thermoplastic, or other elastic or elastomeric material. In one embodiment, when plug 4106 A is mounted within feedthrough hole 4107A and feedthrough member 4103A is mounted within hole 4102A, plug portion 411OA is compressed between assembly 4103 A and edge 4107aA of feedthrough hole 4107A and the plug exerts a radial force on edge 4107aA of the feedthrough hole. This forces or compresses plug 4106 A into an interference or compression fit between feedthrough hole edge 4107 aA and member 4204A, thus helping to seal electrolyte solution within case 4101 A. In other embodiments, the diameter of portion 411OA is smaller than hole 4107 A and an interference fit between feedthrough hole edge 4107aA and member 4204 A is not created. hi one embodiment, as noted above, flange 4108 A provides a sealing means for helping seal electrolyte within the case. Accordingly, in some embodiments, when the diameter of portion 4110A is smaller than hole 4107 A and an interference fit between feedthrough hole edge 4107aA and member 4204 A is not created, only flange 4108 A provides a sealing means between case 4101 A and plug 4106A. Advantageously, the seal or seals are formed automatically. Thus, in one embodiment, assembling and tightening a screw or other extraneous hardware is not required to seal the capacitor.

In one embodiment, second flange 4109A provides support for mounting plug 4106A within hole 4107 A. For instance, when plug 4106A is mounted in hole 4107 A, flanges 4108 A and 4109A each help hold plug 4106A in place once it is mounted, but before the coupling member 4204A is inserted through hole 4102A. This aides the manufacturing process.

In one embodiment second flange 4109A includes a tapered section wherein an outer portion 4109aA of flange 4109A has a smaller diameter than an inner portion 4109bA. The tapered shape of flange 4109A aids in inserting plug 4106A into hole 4107 A. Some embodiments omit the tapered shape and flange 4109 A has a uniform outer diameter. Other embodiments provide a tapered shape for first flange 4108 A. Other embodiments provide tapered sections on both flanges.

In this embodiment, flange 4108 A has a larger diameter than flange 4109A. In some embodiments, the two flanges have substantially equal diameters. In further embodiments, flange 4109 A has a larger diameter than flange 4108 A.

Some embodiments omit either or both of flanges 4108 A and 4109A. For instance, in some embodiments plug 4106 A has a generally cylindrical shape. In other embodiments, plug 4106A has an hour-glass shape or other shape which closely fits within feedthrough hole 4107 A. In some embodiments, plug 4106 A is a mass of elastic material with a dimension approximately equal to or larger than the width of feedthrough hole 4107 A.

In one embodiment, plug 4106 A seals the electrolyte within capacitor case 4101 A, but it does not provide a hermetic seal. Hydrogen is created during consumption of water from the electrolyte and continues to be formed throughout the life of the capacitor. This can cause a hermetically sealed capacitor case to bulge outward from the hydrogen gas production within, thus risking long— term device reliability due to shorting. Accordingly, in one embodiment plug 4106 A permits out— gassing of hydrogen gas, thus alleviating any problems. For instance, in one embodiment, flange 410SA creates a seal to the inner wall of the case 4101 A. A pathway for the gas to escape is then present along the border between coupling member 5 4204A and plug 4106 A.

FIG. 38 shows a cross— sectional side view of a plug 4120A according to one embodiment. Plug 4120A includes one or more features of plug 4106A and discussion of unnecessary details will be omitted. Plug 4120A includes a first flange 4128A, a second flange 4129A, and a portion 4130A between the two

1.0 flanges 4128 A and 4129 A. In one embodiment, plug 4130A includes a hole 4132A. Hole 4132A has a sealing section such as anarrow section 4132bA, which is located between two nominal diameter sections 4132aA and 4132bA. Other embodiments omit section 4132b A or move it to either end, thereby omitting sections 4132aA or 4132b A.

15 hi one embodiment, narrow section 4132bA provides an O-ring type interference fit for a feedthrough member such as coupling member 4204A. In this embodiment, narrow section 4132bA is generally located within second flange 4129 A. Other embodiments locate the narrow section within central portion 4130A. Other embodiments locate the narrow section within first flange 0 4128 A. By way of example, in one embodiment, the nominal diameters of sections 4132aA and 4132cA is approximately 0.032 inches, and the diameter of narrow section 4132bA is 0.026 inches.

Referring again to FIG. 36, one method of assembling a capacitor having a plug 4106A is as follows. Plug 4106A is inserted into feedthrough hole 4107 A 5 of case 4101 A. In one embodiment, plug 4106A includes a double-flange construction which helps hold the plug in place once it is mounted. Feedthrough assembly 4103 A is attached to capacitor stack 4202 A and inserted through inner hole 4102A of plug 4106A while capacitor stack 4202A is placed within the cavity of case 4101A. An interference fit between plug 4106A and feedthrough

30 4103 A and between case 4101 A and plug 4106A are created. Thus, a seal is formed between the interior of case 4101 A and the exterior of case 4101 A.

FIG. 39 shows a feedthrough assembly according to another embodiment of the present subject matter. FIG. 39 shows an exploded view of a flat capacitor 5100A incorporating a feedthrough assembly 5101 A. Although the present embodiment is described as a flat capacitor, other capacitor forms can take advantage of the feedthrough assembly and the other features discussed in the present description.

Capacitor 5100A includes one or more features of capacitor IOOA of FIG. 12 and details will be omitted for the sake of clarity. In the present embodiment, capacitor 5100A includes a feedthrough assembly 5101 A, a conductor 5102A, one or more capacitor element tabs 5104A, a capacitor stack 5105A, a terminal 5112A, and a capacitor housing or case 5113 A. Case 5113A includes a container portion 511OA and a lid 5109 A. Container portion 511OA has a cavity for holding capacitor stack 5105 A. The cavity is defined in part by a bottom side 5115 A surrounded by a side wall 5114A. When lid 5109 A is attached to the container portion of the case, the Hd and the bottom side are substantially parallel to each other.

In one embodiment, case 5113 A includes a feedthrough port or hole 5111 A. Alternatively, the case can include one, two, three, four or more holes, depending on other design factors which will be discussed below.

Capacitor stack 5105 A is situated within capacitor case 5113A. In the exemplary embodiment, capacitor stack 5105 A includes one or more capacitor modules or elements 512OaA, 512ObA, . . ., 512OnA. The number of capacitor elements 5120A can vary according to capacitive need and size of a capacitor desired. Each capacitor element 512OaA- 512OnA includes a cathode 5106 A, an anode 510SA, and a separator 5107A sandwiched between cathode 5106A and anode 5108 A. In some embodiments, other numbers and arrangements of anodes, cathodes, and separators are used. In one embodiment, attached to each capacitive element 512OaA-

512OnA is a foil connection structure such as a conductive tab 5104 A, made from aluminum or other suitable material, which electrically connects each anode to the other anodes of capacitor stack 5105 A. Each tab 5104A of each capacitor element 512OaA- 512OnA is connected to each other tab 5104A and coupled to conductor 5102 A for electrically coupling the anode to a component outside the case.

In one embodiment, conductor 5102 A is an aluminum ribbon tab and is coupled at one end to anode tabs 5104A and at another end to feedthrough assembly 5101 A for electrically coupling capacitor stack 5105 A to a component outside the case through hole 511 IA. Conductor 5102 A is coupled to feedthrough assembly 5101 A by welding or other coupling means.

In one embodiment, each cathode 5106 A is a foil attached to the other cathodes of capacitor stack 5105 A. In the present embodiment, the cathodes are attached to case 5113 A. Terminal 5112 A is attached to case 5113 A. In some embodiments, each cathode 5106 A is joined to the other cathodes at cathode tabs for providing an external cathode connection. In one embodiment, cathodes 5106A are coupled to a feedthrough assembly extending through a feedthrough hole, such as hole 511 IA. hi various embodiments, the anode is connected to the case and the cathode is connected to a feedthrough assembly, or both anodes and cathodes are connected to feedthrough assemblies.

FIG. 40 shows a larger view of feedthrough assembly 5101 A. Feedthrough assembly 5101 A includes an inner core or central feedthrough member 5201 A for electrically connecting conductor 5102 A to an outside component. In one embodiment, central or inner member 5201 A is an annular member which comprises a conductive material, such as aluminum, and has a bore or passage 5204A running through it. Li one embodiment, passage 5204A extends all the way through feedthrough member 5201 A. In some embodiments, passage 5204A extends partially through the member. Feedthrough assembly 5101 A also includes an outer member 5202 A molded, glued, or otherwise located around central member 5201 A. In one embodiment, outer member 5202 A is an electrically insulating material, such as a plastic or thermoplastic, for insulating the central member 5201A from case 5113 A. Member 5202A is an annular, flanged member having a cylindrical stepped— shaped structure. In one embodiment, outer member 5202A includes a substantially flat surface 5205A and a second surface 5207A substantially perpendicular to surface 5205A.

FIG. 41 shows a partial cross-section view of capacitor 5100A connected by feedthrough assembly 5101 A to a component, such as heart monitor circuitry 5308 A. In the present embodiment, outer member 5202A is attached to case

5113A by an epoxy or other adhesive method at areas 5309A and 5310A. Some embodiments include threads on surface 5207A and/or form member 5202A from an elastic material that is compressed within hole 511 IA. In some embodiments, the elastic material is permeable to allow passage of fluids such as hydrogen gas to escape from case 5113 A. Outer member surface 5205 A abuts an inner surface of case 5113 A around feedthrough hole 511 IA and surface 5207 A abuts or confronts an edge surface of the feedthrough hole.

Tabs 5104A are connected to one end of conductor 5102 A. In various embodiments, conductor 5102 A is welded, crimped, or otherwise attached to the tabs. A second end of conductor 102 A is welded or crimped or otherwise attached to a substantially flat surface 5307A of conductive central member 5201 A. In one embodiment, conductor 5102 A is folded over itself between tabs 5104A and feedthrough assembly 5101A. In some embodiments, the fold is omitted to reduce the space between tabs 5104A and feedthrough assembly 5101 A. In one embodiment, conductor 5102 A is omitted and central member 5201 A is directly attached to tabs 5104 A.

Central member 5201 A electrically connects conductor 5102 A to outside component 5308A. In the exemplary embodiment, central member 5201 A is a cylindrical stepped-shaped member having a first annular section and a second annular flange section. Member 5201 A has a first end 5320A within case 5113 A and a second end 5330A extending through hole 511 IA. In one embodiment, second end 533OA has a substantially flat end surface which is positioned flush with an outer surface of case 5113 A. In other embodiments, second end 533OA is partially within feedthrough hole 511 IA. In some embodiments, second end 5330A protrudes from hole 511 IA and extends a distance from case 5113 A.

In one embodiment, central member passage 5204A includes a mounting section 531 IA, such as a threaded section. A feedthrough terminal fastener 5304A includes a mounting section (in one embodiment, a threaded section) that corresponds to mounting section 531 IA of passage 5204A so that feedthrough terminal fastener 5304 A is removably attachable to the central member of feedthrough assembly 5101 A. In some embodiments, a sealant such as Loctite is placed on the mounting section to provide for a sealed connection.

Terminal fastener 5304A attaches a feedthrough terminal 5303A to feedthrough assembly 5101 A. Terminal 5303A in turn is attached (for example, soldered or welded) to a connector 5302A which is connected to component 5308A. In one embodiment, terminal 5303A is a conductive material, such as aluminum or gold— plated nickel. Other embodiments have other suitable conductive materials. Since terminal fastener 5304A is removable, it allows a defective capacitor to be replaced by a good one.

For instance, if capacitor 5100A were installed in a defibrillator and it was discovered that the capacitor was defective, a user could disengage feedthrough terminal 5303A from the capacitor and mount a new capacitor in place of the defective one. This is in contrast with conventional feedthrough assemblies in which one would have to cut connector 5302A from terminal 5303 A and then reweld or re-solder the connector to a new capacitor. Moreover, the conventional design requires an extra length for connector 5302A to allow for replacement. This extra length takes up extra space within the device, for example an implantable defibrillator or cardioverter, including the capacitor. Thus, the exemplary embodiment permits an optimal, minimal length of connector 5302 A while still permitting a defective capacitor to be replaced without having to throw the whole device away. In one embodiment, conductor 5102 A includes one or more holes, such as a hole 5301 A, adjacent to and contiguous with passage 5204A. In some embodiments, hole 5301 A is as small as a pinhole. In the present embodiment, hole 5301 A is aligned with passage 5204A and provides a continuous passage that effectively extends passage 5204A into the interior of case 5113 A, allowing introduction of an electrolyte solution (or other material) into case 5113 A through passage 5204A and hole 5301 A. Thus, a user can fill case 5113A with electrolyte through an existing feedthrough hole instead of providing and sealing a separate backfill hole. Thus, the present embodiment saves at least one manufacturing step. In some embodiments, conductor 5102 A is attached to feedthrough assembly 5101 A so that it is slightly offset from passage 5204A, thus providing a continuous passage into the interior of case 5113 A. In some embodiments, conductor 5102A includes two, three, or more holes.

FIG. 42 shows a partial cross— section view of a feedthrough assembly 5400A according to another embodiment. Feedthrough assembly 5400A includes a central feedthrough member 5402A and an outer member 5401 A. In one embodiment, member 5402A is a cylindrical, step-shaped member made from a conductive material such as aluminum. Central member 5401A has a passage 5403 A extending through it. Conductor 5102 A is attached to member 5402A and includes one or more holes 5301 A adjacent to and contiguous with passage 5403A so that an electrolyte solution can be deposited within case 5113A through the passage 5403A and the hole 5301 A.

In this embodiment, passage 5403 A is a non-threaded cylindrical passage adapted to have a terminal fastener (not shown) riveted, interference fitted, glued, or otherwise coupled to it. In one embodiment, a connector from an outside component is directly coupled within passage 5403 A by an interference or friction fit. In some embodiments, passage 5403A has a square, triangle, or other shape for receiving a terminal fastener.

FIG. 43 shows a partial cross-section view of a feedthrough assembly 5500A according to another embodiment. Feedthrough assembly 550OA includes a central feedthrough member 5501 A and an outer member 5502A. In one embodiment, member 5501 A is a cylindrical, step— shaped member made from a conductive material such as aluminum. Outer member 5502A is an electrically insulative material, molded, glued, or otherwise placed around conductive central member 550 IA to electrically insulate member 550 IA from a conductive capacitor case.

In this embodiment, feedthrough member 5501A includes a passage. 5503 A. Passage 5503 A extends partially through a central axial portion of the central member. In the exemplary embodiment, passage 5503A is threaded. This provides a mounting portion for removably mounting a threaded member such as a terminal fastener. In some embodiments, passage 5503A is not threaded and a terminal fastener or a terminal is interference fitted, glued or otherwise attached within passage 5503 A.

FIG. 44 shows an example of a method 5700A for manufacturing an electrolytic capacitor according to one embodiment of the present subject matter. Method 5700A will be discussed in reference to exemplary capacitor 5100A of FIGS. 39-41. However, it is understood that the method can be performed on different types of capacitors. In block 5702A, method 570OA includes providing a capacitor case 5113 A having a hole 511 IA. In block 5704A, the method includes installing feedthrough assembly 5101 A at least partially into hole

511 IA. The feedthrough assembly 5101 A includes conductive member 5201 A having passage 5204A therethrough. In block 5706A, method 5700A includes filling case 5113 A with an electrolyte solution through passage 5204A. In block 5708A, method 5700A includes installing terminal fastener 5304A in passage 5204A. The exemplary method saves at least one manufacturing step since the electrolyte is filled through an existing feedthrough hole instead of providing and sealing a separate backfill hole.

FIG. 45 shows an exemplary method 5800A for replacing a first capacitor installed in a medical device with a second capacitor. Again, the method will be discussed in reference to capacitor 5100A. In block 5802 A, the method includes disengaging a terminal 5303 A coupled to a medical device 53O8A from a feedthrough passage 5204A of the first capacitor 5100A. In block 5804A, the method includes installing the same terminal 5303A into a feedthrough passage of the second capacitor (not shown). This provides that the capacitor can be replaced instead of having to throw the whole unit away. FIG. 46 shows a method 5900A for manufacturing an implantable defibrillator according to one embodiment of the present subject matter. Again, the method will be discussed in reference to capacitor 5100A. In block 5902A, the method includes providing a defibrillator case having circuitry 5308 A. In block 5904A, the method includes providing a capacitor case 5113 A having a hole 511 IA. In block 5906A, the method includes installing feedthrough assembly 5101 A at least partially into hole 511 IA. In the exemplary method, the feedthrough assembly 5101 A includes a conductive member 5201 A having a passage 5204A. In block 5908A, the method includes mounting terminal 5303A to passage 5204A using a terminal fastener 5304A. In block 5910A, the method includes coupling a conductor 5302A coupled to defibrillator circuitry 5308A to terminal 5303 A.

FIGS. 47-51 show one or more embodiments for coupling a cathode or anode stack to a capacitor case.

FIG. 47 shows a perspective view of a capacitor 5018 A. Capacitor 5018 A includes one or more features described above for capacitor IOOA of FlG. 12. Accordingly, certain details will be omitted herein. Capacitor 5018A includes a capacitor container 5020A including a case 5022A and a lid, or cover 5024A overlying case 5022 A for placement on an upper rim 5026 A of case 5022A. A capacitor stack 5028A with a top surface 5030A is enclosed by container 5020A which defines a chamber 5O32A.

Capacitor stack 5028A includes a plurality of cathode and anode foil layers separated by one or more separators. The anode foil layers are connected together and coupled to a feedthrough conductor 5034A. In one embodiment, feedthrough conductor 5034A passes through a hole in case 5022A, and conductor 5034A is electrically isolated from case 5022A.

The cathode foil layers of stack 5028 A are connected together and connected to a conductor 5036A. In one embodiment, cathode conductor 5036A is a tab strip which is integral to one of the cathode layers. In other embodiments, cathode conductor 5036 A is a strip of aluminum tab stock connected to one or more of the cathode foil layers. Cathode conductor 5036A provides an electrical connection between the cathode layers and case 5022A. FIG. 48 shows a capacitive element 5038 A in accord with one embodiment. Capacitor stack 5028A includes a plurality of generally flat capacitive elements 5038A. Capacitive element 5038A includes foil layers such as cathode layer 5040A and anode layers 5042A each of whose electrical elements are connected in parallel. In this embodiment, anode layers 5042 A form a triple anode structure. Other embodiments include single, double, triple, four, and/or more anode foils.

FIGS.49—51 show a partial cutaway view of capacitor 5018A during respective manufacturing stages in accord with one or more embodiments of the present subject matter. Capacitor stack 5028A includes top surface 503OA and a lateral face 5046A and includes one or more parallel connected capacitive elements, such as capacitive element 5038A shown on FIG. 48. As discussed above, in one embodiment, the anodes of each capacitive element have respective tabs connected together and welded at their free ends. The welded tabs are then welded (or otherwise fastened or attached) to feedthrough conductor 5034A that passes through case 5022A. (See FIG. 47). In some embodiments, an unetched, integral portion of each of one or more anodes is used to weld or attach the anode layers to one another.

In one embodiment, cathode tabs are attached or fastened to cathode conductor 5036A. As noted above, in some embodiments cathode conductor 5036 A is an integral extension of a cathode foil layer, meaning for example, that the cathode conductor and cathode foil layer are formed from a single piece of foil.

In one embodiment, cathode conductor 5036A extends from capacitor stack 5028 A and is positioned and pinched between upper rim 5026A of case 5022A and cover 5024A. Cover 5024A and case 5022A form an interface or seam 5048A at upper rim 5026A. Cathode conductor 5036A is positioned in interface 5048A between case 5022A and cover 5024A. Cathode conductor 5036A is pinched between case 5022A and cover 5024A defining an inner conductor portion 5O50A and an outer conductor portion 5052A. As shown in FIG. 50, in one embodiment, at least a portion of the outer conductor portion 5052A is trimmed off of the cathode conductor 5036A.

In some embodiments, cathode conductor 5036A is welded into place during the base/cover welding process, providing a mechanical and electrical connection to the case 5022A without a separate connection procedure. In contrast, if the cathode conductor is connected to the case in a separate procedure, the extra connection requires that part of the capacitor stack be removed or the case be enlarged to allow space for routing and connecting the conductors, thereby reducing the packaging efficiency of the capacitor. The reduced packaging efficiency ultimately results in a larger capacitor. In some embodiments, conductor 5036 A is welded or otherwise fastened to the interior or exterior of cover 5024 A or to the exterior of case 5022 A.

FIG. 51 shows a partial cutaway view of capacitor 5018 A with cover 5024A welded to case 5022A. Cathode conductor 5036A is positioned between case 5022A and cover 5024A at upper rim 5026A. Cathode conductor 5036A is welded in the interface 5048A between cover 5024A and case 5022A, providing a mechanical and electrical connection to the container 5020A. The welded conductor 5036A, cover 5024A and case 5022A are welded together with a single bead 5054A. In one embodiment, the bead forms a hermetic seal between the cover 5024A and case 5022A.

Among other advantages, one or more of the embodiments described above provide a capacitor structure which reduces the space required for connecting and routing the cathode conductor and thus allows a reduction in the size of the capacitor, or alternatively an increase in its energy storage capacity. The embodiments described above show the cathode conductor electrically connected to the housing forming a cathodic housing. Alternative embodiments include positioning the anode conductor between the cover and case thereby connecting the anode layers and anode conductor to the housing forming an anodic housing. An exemplary embodiment of a method to connect a cathode conductor to a capacitor housing is described below. The cathode conductor is connected to the housing by positioning the conductor between the case and the cover; positioning the cover on the case; and attaching the cover to the case so that the conductor is electrically and mechanically connected to the housing. In addition, other embodiments include positioning the conductor between the case and the cover at the upper rim and attaching the cover to the case at the upper rim. In one embodiment, the case and the cover form an interface and the positioning of the conductor between the case and the cover is in the interface. In another embodiment, the attaching the cover to the case comprises welding or soldering the cover to the case. The cathode conductor is welded into place using a single bead during the welding of the cover to the case, eliminating a separate step of connecting the cathode conductor to the case.

One example method of providing internal interconnections and/or external connections is described as follows. Fig. 52 shows a top view of a foil connection according to one embodiment. In this embodiment, a wire connector 5260A is attached to a major surface of an anode layer 5 HOA along a portion of the wire connector's length. In one embodiment, wire connectors are similarly connected to the cathode layers of the capacitor stack. In one embodiment, wire connector 5250A is made of a high purity aluminum, is a round wire and includes a diameter allowing the desired amount of bending and twisting as the connectors is routed through the capacitor case.

FIG. 53 shows a capacitor in accordance with one embodiment in which one or more round wire connectors 5250A are connected to the cathode layers 5120 A and wire connectors 5260A are connected to anode layers 511 OA. The wire connectors may be made of high purity aluminum and are staked (or otherwise attached such as by welding, brazing, etc.) to the individual cathode and anode layers.

Wire connector 5250A and 5260A connect like types of layers together and can be used to connect the layers to external terminals. In the FIG., the wires connected to the anode layers exit the layers at one common location while the cathode layer wires exit together at a different location. The anode layer wires 5260A and cathode layer wires 5250A are then gathered into corresponding wire bundles 5261 A and 5251A, respectively. The bundles can then be twisted together into a cable that can be laid in any direction to be routed through feedthroughs 5280A to terminal connections. In the FIG., the anode layers 511OA are electrically connected to positive terminal 5160A, and the cathode layers are electrically connected to negative terminal 5150A. By directly connecting the round wire connectors to the capacitor layers, there is no need for tabs that add to the space requirements of the capacitor case.

In one embodiment, wire connectors 5250A and/or 5260A are insulated with the insulation removed at the point of bundling in order to electrically connect like types of layers together. In another embodiment, the wires are uninsulated and routed through the case via an insulated feedthrough hole.

Advantageously, in one or more embodiments, the cathode and anode wires can be gathered into bundles and twisted into a cable that can be routed in any direction through a feedthrough of the capacitor case. This allows greater space efficiency and a smaller case for the capacitor. Referring to FIG. 12, in one embodiment, terminal 104A is attached to case 101 A along a side portion of the case. FIG. 54 shows capacitor 5018A having a terminal connection 5030A in accord with another embodiment. In this embodiment, feedthrough conductor 5034A is attached to the anode layers inside the case as described above. The cathode layers are connected to the case in this embodiment, and terminal connector 5030A is attached to the case in an end-on fashion by welding or brazing the end of the wire to the capacitor case.

In one embodiment, terminal connector 5030A includes a body having an end surface which is substantially perpendicular to the body. The end surface is positioned so that the end surface is flushly positioned against the surface of the case and is butt— welded to the case, wherein terminal connector is only attached to the case at its end surface and not along any portions of its body.

In one embodiment, an expanded end 5040A at the end of the wire is provided. The expanded end 5040A in this embodiment is in the shape of a nailhead with a flat surface for attaching to the case. The surface area of the expanded end is sufficient to provide a securely welded connection while minimally altering the footprint of the capacitor case. The overall volume of the device housing can thus be reduced. In FIG. 55, terminal wire 5030A with an expanded end 5040A at its end is attached directly to a capacitor case 5020A by, for example, arc percussive welding or laser welding.

In FIG. 56, expanded end 5040A is attached with braze 5016A to a piece of intermediate material 5014A welded to the case 5020A. Both methods of attachment result in a low height profile that minimizes the amount of interconnect space required for connection of the capacitor to an external terminal.

Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiment shown. This application is intended to cover adaptations or variations of the present subject matter. It is to be understood that the above description is intended to be illustrative, and not restrictive.

Combinations of the above embodiments, and other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the present subject matter should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims

What is claimed is:

1. An apparatus, comprising: a capacitor including a first capacitor partition of a first capacitance for delivering a first defibrillation pulse of a first amount of energy when charged to a first voltage, and a second capacitor partition of a second capacitance to deliver a second defibrillation pulse of a second amount of energy when charged to the first voltage; and a switch for switching the capacitor between a first mode for delivering the first pulse and a second mode for delivering the second pulse.

2. The apparatus of claim 1, further comprising: an impedance sensor adapted to deliver a signal; capacitor means for delivering a first defibrillation pulse of a first amount of energy when charged to a first voltage, and a second defibrillation pulse of a second amount of energy when charged to a second voltage, the first and second voltages being substantially the same; and switch means for switching the capacitor means between a first mode for delivering the first pulse and a second mode for delivering the second pulse, the switching based on the signal of the impedance sensor.

3. The apparatus of any one of claims 1-2, wherein the capacitor means includes a stack of electrodes including a first and second anode which are electrically isolated and connected to a respective first and second feedthrσugh, and a common cathode.

4. The apparatus of claim 3, wherein the common cathode is connected to the case.

5. The apparatus of any one of claims 1-4, wherein the first amount of energy is approximately 31 joules.

6. The apparatus of any one of claims 1 -5, wherein the second amount of energy is approximately 41 joules.

7. The apparatus of any one of claims 1-6, wherein the impedance is measured at a first lead.

8. The apparatus of claim 7, wherein the switch means compares a nontruncated discharge time of a first capacitor of an implantable device adapted for discharge through the first lead to a threshold time, and if the discharge time is higher than the threshold time, switches the first capacitor from the first mode to the second mode.

9. The apparatus of any one of claims 7-8, wherein the first mode includes a second capacitor in parallel with the first capacitor, with each connected to the first lead, and the second mode includes only the first capacitor connected with the first lead.

10. The apparatus of any one of claims 1-9, wherein the capacitor means includes a first and second capacitor in a stack, the first and second capacitors including a plurality of substantially planar electrodes.

11. The apparatus of any one of claims 1-10, wherein the first capacitor is adapted to substantially discharge a first amount of energy to a load of approximately 40 to approximately 60 ohms in less than approximately 20 milliseconds, and the first and second capacitors are adapted to substantially discharge a second amount of energy to the load in more than approximately 20 milliseconds when connected in parallel.

12. The apparatus of any one of claims 1-11, comprising: a capacitor case; a first capacitor stack of the capacitor disposed in the capacitor case and including at least a first anode layer and at least a first cathode layer, the first anode layer including a first anode connection member; a first feedthrough disposed through the capacitor case and connected to the first anode connection member; a second capacitor stack of the capacitor stacked onto the first capacitor stack in alignment, the second capacitor stack including at least a second anode layer and at least a second cathode layer, with a second anode connection member which is aligned with the first anode connection member along the direction of stacking; a second feedthrough disposed through the capacitor case and connected to the second anode layer; and an electrolyte disposed in the capacitor case, the electrolyte in contact with at least the first anode layer and at least the second anode layer, wherein the first and second cathode layers are electrically connected, and the first and second feedthroughs are electrically isolated.

13. The apparatus of claim 12, wherein the first capacitor stack includes the first anode layer and the second capacitor stack includes the second anode layer, and each are adapted to deliver respectively to the first and second feedthrough from about 5.3 joules per cubic centimeter of stack volume to about 6.3 joules per cubic centimeter of stack volume.

14. The apparatus of any one of claims 12-13, further comprising a separator paper disposed between a first anode connection member and the second anode connection member.

15. The apparatus of any one of claims 12-14, wherein the first and second cathode layers are connected to the capacitor case and as such the capacitor case is cathodic.

16. The apparatus of any one of claims 12-15, wherein the switch connects the first feedthrough and the second feedthrough when the switch is closed.

17. The apparatus of any one of claims 12-16, wherein the first feedthrough is connected to the capacitor case with a first seal, the second feedthrough is connected to the capacitor case with a second seal.

18. The apparatus of claim 17, wherein the first and second seal are adapted to resist the flow of electrolyte.

19. The apparatus of any one of claims 12-18, further comprising a hermetically sealed housing in which the capacitor case is disposed along with electronics, the electronics including power source control electronics connected to the first and second feedthroughs and the capacitor case.

20. The apparatus of claim 19, further comprising wireless communication electronics disposed in the hermetically sealed housing and adapted to control the power source control electronics.

21. The apparatus of any one of claims 1 -20, comprising: a capacitor case; a capacitor roll including the first and second capacitor partitions, the capacitor roll disposed in the capacitor case, the capacitor roll including at least a first cathode layer, at least a first anode layer, and at least a second anode layer; a first feedthrough disposed through the capacitor case and connected at least to the first anode layer; a second feedthrough disposed through the capacitor case and connected at least to the second anode layer; a single electrolyte disposed in the capacitor case and substantially filling interstices in the capacitor case, wherein the first and second anode layers are electrically isolated.

22. The apparatus of claim 21, further comprising a third feedthrough disposed through the capacitor case and connected at ieast to the first cathode layer.

23. The apparatus of any one of claims 21 -22, wherein the capacitor case is cathodic, and at least a first cathode layer is connected to the capacitor case.

24. The apparatus of any one of claims 21-23, further comprising a third anode layer which is electrically isolated from the first anode layer, and which is further electrically isolated from the second anode layer, with a fourth feedthrough disposed through the capacitor case and connected to the third anode layer.

25. The apparatus of any one of claims 21-24, further comprising an implantable medical device including an implantable device housing in which the capacitor case is disposed.

26. The apparatus of claim 25, further comprising cardiac rhythm management electronics to which the first and second anode are connected.

27. The apparatus of any one of claims 25-26, further comprising stimulation pulse management electronics adapted to electrically connect one of the first feedthrough and the second feedthrough to a stimulation electrode positioned outside the implantable device housing.

28. The apparatus of any one of claims 1-27, comprising: a capacitor case; the first capacitor partition disposed in the case and including at least a first anodic electrode and at least a cathodic electrode; the second capacitor partition disposed in the case and including at least a second anodic electrode; a first feedthrough disposed through the case and connected to the first anodic electrode; and a second feedthrough disposed through the case and connected to the second anodic electrode; wherein the first and second feedthroughs are electrically isolated and the first capacitor partition has a first capacitance which is approximately three times a second capacitance of the second capacitor partition.

29. The apparatus of claim 28, wherein the first capacitor partition is adapted to store approximately 10 joules.

30. The apparatus of any one of claims 28-29, wherein the second capacitor partition is adapted to store around 31 joules.

31. The apparatus of any one of claims 28-30, wherein the first feedthrough and the second feedthrough are adapted to deliver from about 5.3 joules per cubic centimeter of stack volume to about 6.3 joules per cubic centimeter of stack volume.

32. The apparatus of claim 31, wherein the first capacitor partition is adapted to deliver from about 7.0 joules per cubic centimeter to about 8.5 joules per cubic centimeter when measured at the first anodic electrode.

33. The apparatus of any one of claims 28-32, further comprising a switch connecting the first and second feedthrough in parallel.

34. The apparatus of claim 33, wherein the switch is disposed inside the case.

35. The apparatus of claim 34, wherein the switch includes a semiconductor switch connected to the first anode layer and the second anode layer.

36. The apparatus of any one of claims 1-35, comprising: a plurality of capacitors including the first capacitor partition and the second capacitor partition; and a switching circuit connected between the plurality of capacitors, wherein the switching circuit is adapted to programmably connect two or more capacitors of the plurality of capacitors to provide a desired defibrillation capacitance.

37. The apparatus of claim 36, wherein the plurality of capacitors are housed in an implantable medical device.

38. The apparatus of claim 37, wherein the switching circuit is housed with the plurality of capacitors.

39. The apparatus of any one of claims 37-38, wherein the switching circuit is housed separate from the plurality of capacitors.

40. The apparatus of claim 39, wherein the switching circuit is housed adjacent to the plurality of capacitors.

41. The apparatus of any one of claims 37-40, wherein the switching circuit is accessible from outside the implantable medical device via wireless communication.

42. The apparatus of any one of claims 37-41, wherein the switching circuit is accessible from outside a human body in which the device is implanted via wireless communication.

43. The apparatus of any one of claims 1-42, comprising: a plurality of capacitors including the first capacitor partition and the second capacitor partition; and a switching circuit connected between the plurality of capacitors, wherein the switching circuit is adapted to programmably connect two or more capacitors of the plurality of capacitors to selectively charge connected elements for use in a defibrillator.

44. The apparatus of claim 43, further comprising: a flyback capacitor charger adapted to connect in parallel with the two or more capacitors of the plurality of capacitors.

45. The apparatus of any one of claims 43-44, wherein the plurality of capacitors includes a first and second capacitor in a stack.

46. The apparatus of any one of claims 43-45, wherein the first and second capacitors include a plurality of substantially planar electrodes.

47. The apparatus of any one of claims 1-46, comprising: a first and second capacitor partition in a stack, the first and second capacitors including a plurality of substantially planar electrodes; and a switching circuit connected between the first and second capacitors, the switching circuit having at least two states, wherein the switching circuit is adapted to provide a first defibrillation capacitance in a first state and a second defibrillation capacitance other than the first in a second state.

48. The apparatus of claim 47, wherein the stack includes a common cathode which is shared by the first and second capacitor.

49. The apparatus of any one of claims 47-48, wherein the first defibrillation capacitance is equal to a capacitance of the first capacitor and the second defibrillation capacitance is equal to the sum of the capacitance of the first capacitor and a capacitance of the second capacitor.

50. The apparatus of any one of claims 1-49, comprising: the first and second capacitor partition in a stack, the first and second capacitor partitions including a plurality of substantially planar electrodes; a switching circuit connected between the first and second capacitor partitions, the switching circuit including: a field effect transistor (FET) adapted to have a source connected to the first capacitor partition and a drain connected to the second capacitor partition; a bipolar junction transistor (BJT) adapted to have an emitter connected to the source of the FET and a collector connected to a gate of the FET; a first current source connected to the collector of the BJT, wherein activating the first current source turns the FET on, connecting the first and second capacitor partitions; and a second current source connected to a base of the BJT, wherein activating the second current source turns the FET off, isolating the first and second capacitor partitions.

51. The apparatus of claim 50, wherein the stack includes a common cathode which is shared by the first and second capacitor partition.

52. The apparatus of any one of claims 50-51 , further comprising: a diode adapted to connect the source of the FET to the drain of the FET, the diode adapted to conduct during discharge of the second capacitor partition.

53. The apparatus of any one of claims 50-52, further comprising: a diode adapted to connect the collector of the BJT to the emitter of the BJT.

54. The apparatus of any one of claims 50-53, further comprising: a resistor adapted to connect the base of the BJT to the emitter of the

BJT, wherein a resistance value of the resistor is selected to prevent the BJT from turning on due to off-state leakage current from the second current source.

55. A method for pulse generation in an implantable device, comprising: measuring an impedance between a first electrode and a second electrode; and delivering a pulse based on a pulse energy level and a pulse duration limit, comprising: generating a pulse duration limit as a function of the pulse energy level and the impedance; and selecting a capacitance value from a plurality of capacitances in a partitioned capacitor bank to deliver the pulse at the pulse energy level, the capacitance value selected such that the pulse duration is less than the pulse duration limit.

56. The method of claim 55, further comprising programming the implantable device using a wireless programmer.

57. The method of any one of claims 55-56, wherein the pulse duration limit is approximately 0.020 milliseconds. .

58. The method of any one of claims 55-57, wherein the impedance is between approximately 40 ohms and approximately 60 ohms.

59. The method of any one of claims 55-58, wherein the pulse duration is a function of a tilt setting, and a constant tilt setting is selected for a first capacitance and at least a second capacitance.

60. The method of claim 59, wherein the constant tilt setting is between 60% and 80%.

61. The method of claim 60 wherein the constant tilt setting is approximately 66%.

62. The method of any one of claims 55-61, further comprising switching the partitioned capacitor from a first capacitance to a second capacitance by switching a first anode into parallel operation with a second anode.

63. The method of claim 62, further comprising switching the first anode into parallel operation with a second anode without switching the cathode into parallel operation with an additional cathode.

64. The method of any one of claims 62-63, further comprising switching a jumper to switch the first anode into parallel operation with the second anode.

65. The method of claim 64, wherein the jumper is accessible outside a housing of the implantable device.

66. The method of any one of claims 55-65, wherein a first capacitance of two capacitances is approximately three times the second capacitance.

67. The method of claim 66, wherein the partitioned capacitor stores 31 joules using the first capacitance.

68. The method of any one of claims 55-67, comprising: stacking into a stack a plurality of substantially planar capacitor electrodes to define the partitioned capacitor bank, the stack include at least a first and second anode layer and a plurality of cathode layers, with a first anode connection member of the first anode layer being aligned along the direction of stacking with a second anode connection member of the second anode layer; positioning the stack in a case; connecting the first anode layer to a first feedthrough disposed through the case; connecting the second anode layer to a second feedthrough disposed through the case; connecting the plurality of cathode layers to the case; and connecting the first feedthrough, the second feedthrough, and the case to power source control circuitry including a switch which connects the first and second feedthrough in parallel in a first mode of operation.

69. The method of claim 68, further comprising sealing the stack in the case.

70. The method of claim 69, further comprising disposing the case in an implantable device.

71. The method of any one of claims 68-70, further comprising welding together a first anode connection member of the first anode layer, a second anode connection member of the second anode layer, and a plurality of cathode connection members, each of a cathode layer of the plurality of cathode layers.

72. The method of claim 71, further comprising electrically isolating the plurality of cathode layers from the first anode layer and the second anode layer by cutting the plurality of cathode connection members.

73. The method of claim 72, further comprising electrically isolating the first anode layer and the second anode layer using a laser cut.

74. The method of claim 73, further comprising disposing a separator paper between the first anode connection member and the second anode connection member.

75. The method of any one of claims 55-74, comprising: forming a first and second capacitor in a stack to define the partitioned capacitor bank, the first and second capacitors including a plurality of substantially planar electrodes; forming a switching circuit between the first and second capacitors, the switching circuit having a first and second state; selecting the first capacitor and the second capacitor to provide a defibrillation capacitance by selecting the first state of the switching circuit; and selecting the first capacitor to provide the defibrillation capacitance by selecting the second state of the switching circuit.

76. The method of claim 75, wherein forming the first capacitor includes forming the first capacitor to store around 31 Joules.

77. The method of any one of claims 75-76, wherein forming the second capacitor includes forming the second capacitor to store around 10 Joules.

78. The method of any one of claims 55-77, comprising: forming a first and second capacitor in a stack to define the partitioned capacitor bank, the first and second capacitors including a plurality of substantially planar electrodes; connecting a switching circuit between the first and second capacitors, wherein connecting the switching circuit includes: connecting a field effect transistor (FET) between the first and second capacitors; connecting a bipolar junction transistor (BJT) between a gate and source of the FET; connecting a first current source to the gate of the FET; connecting a second current source to a base of the BJT; selectively activating the first current source to turn the FET on, connecting the first and second capacitors; and selectively activating the second current source to turn the FET off, isolating the first and second capacitors.

79. The method of claim 78, wherein connecting a FET includes connecting a p-channel MOSFET.

80. The method of any one of claims 78-79, wherein connecting a BJT includes connecting a PNP transistor.

81. The method of any one of claims 78-80, wherein forming a first and second capacitor in a stack includes: stacking into the stack a plurality of substantially planar capacitor electrodes, the stack include at least a first and second anode layer and a plurality of cathode layers; positioning the stack in the case; connecting the first anode layer to a first feedthrough disposed through the case; connecting the second anode layer to a second feedthrough disposed through the case; and connecting the plurality of cathode layers to the case.

82. The method of claim 81 , wherein connecting a switching circuit between the first and second capacitors includes connecting the first feedthrough, the second feedthrough, and the case to the switching circuit.