JP3731988B2 - Method and circuit for supplying drive current to a voice coil for positioning a head of a disk drive - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improved driver circuit and method for a voice coil of the type used to move a read / write head in a disk drive of the type used in a computer system, and more particularly to a power driver transistor for a voice coil in a disk drive system. Current sensing accuracy for voice coils in a disk drive system and for head positioning controlled thereby (accuracy) The present invention relates to an improved circuit and method.
[0002]
[Prior art]
Typical disk drives, such as those used for floppy disks, hard disks, and CD-ROM disks used in personal computers and the like, have one or more rotating disks on which data is selected. Can be recorded and read automatically. Typically, a CD-ROM has one or more rotating discs on which data is optically pre-recorded and can only be read. Recently, however, a CD-ROM system that can write data to an optical disk has been introduced, nevertheless it is called "CD-ROM". However, in all such disk drives, one or more heads are provided which record and read data in the case of magnetic disks and simply detect data in the case of CD-ROM drives. In either case, the heads are typically carried by an arm structure that can be selectively positioned into one of a number of circular data paths located at different radial positions of the disk from the spindle carrying the disk. Is done.
[0003]
The arm carrying the head, and thus the head itself, is moved along a line extending across the disk radius by a so-called “voice coil”. By supplying a current of known magnitude and polarity to the voice coil, the head can be selectively positioned with respect to the disk anywhere on the line.
[0004]
In a typical system, the current to the voice coil is controlled by a current driver circuit that includes four driver transistors. These driver transistors are, for example, supply voltage or V _CC FET device connected to form an “H” bridge between the two and the ground, the voice coil is connected between the “H” legs, and each driver transistor is each “H” upright What is necessary is just to be connected to the part. FET devices connected to the supply voltage and to each side of the voice coil are commonly referred to as “high-side drivers”, and FET devices connected between each side of the voice coil and ground are , Commonly referred to as “low-side driver”. Each high side driver and low side driver of each leg of the driver is typically controlled by two oppositely driven power amplifiers.
[0005]
The most common approach to controlling head movement uses a sense resistor in series with the voice coil to sense the current through the voice coil. The sensed current is fed back to the driver amplifier so that the voice coil current can be accurately controlled. The use of a sense FET to sense the coil current reduces the resistive drop in the voice coil, which allows the user to supply more current to the coil.
[0006]
That is, an FET device can be connected to mirror the current of the power transistor as a current mirror to detect the current flowing through the power transistor in the current path of the motor. These mirror transistors are typically made small compared to the size of the power transistor, and the ratio is typically 15/1. However, while it is desirable to make the mirror transistor very small compared to the power transistor, as the size ratio increases, design tolerances between the various mirror transistors become inaccurate.
[0007]
Nevertheless, the use of such FET mirror devices often degrades accuracy because of the large size difference between the power device and the mirror device. Normally, the current through one transistor can be mirrored to another transistor with relatively good accuracy if the devices are of similar size. However, in voice coil applications, several amperes of current flow through the primary device in the power FET device and a large ratio (eg, on the order of 1500: 1) between the power FET and the mirror device. It is desirable to use it. If a small ratio is used, a large amount of power is wasted in the control circuit due to the large current in the mirror device. However, when using a mirror ratio on the order of 1500: 1, the accuracy of the mirror is not very good and can be expected to be large and vary from device to device.
[0008]
Furthermore, the voice coil drive circuit may require multiple gain ranges, eg, three or more ranges, depending on the particular system. These gain ranges allow the DAC that controls the voice coil loop to operate with equal accuracy over several ranges of coil current. That is, if sense FET technology is used, many voice coils increase the gain of the feedback current because the feedback current becomes smaller and possibly inaccurate as the coil current approaches zero. In this way, the current mirror in the feedback block is not forced to handle currents from a few microamperes to a few hundred microamperes. This helps to match the current mirror and thus helps for accuracy of current control. That is, in the past, current mirror operation of the drive transistor has been inaccurate, especially at the low current levels experienced in variable gain voice coil drive circuits.
[0009]
Therefore, what is needed is a circuit and method that provides sensing current accuracy with a relatively small size mirror transistor that can be used with a circuit that provides multiple gain ranges in which the feedback circuit operates if desired. .
[0010]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a circuit and a method for realizing the accuracy of sensing current in a voice coil driving circuit by using a mirror transistor having a relatively small size.
[0011]
Another object of the present invention is to provide a circuit and method of the type described above that can be used with a circuit that provides multiple gain ranges in which the feedback circuit operates if desired.
[0012]
These and other objects, features and advantages of the present invention will become apparent to those skilled in the art from the following detailed description when read in conjunction with the accompanying drawings and appended claims.
[0013]
[Means for Solving the Problems]
A general feature of the present invention is that it provides a method of supplying drive current to a voice coil that positions a head of a disk drive. The method includes measuring a first current supplied to the voice coil and mirroring the first current to provide a sense current proportional to the first current. The method also modifies the magnitude of the first current in a feedback circuit using the sense current to position the head near a desired position, and more precisely equals the sense current to the desired magnitude. Adjusting and positioning the head closer to the desired position. The current can be adjusted, for example, to force the current of the voice coil coil as close to 0 as possible when the head is disposed at the desired position.
[0014]
The step of adjusting the sense current may be performed by selectively connecting at least one active device having a current path in parallel with the active device connected to mirror the power transistor current. This can be done, for example, by selectively connecting a trim FET having a first channel width to length ratio in parallel with a current mirror FET having a second channel width to length ratio. The step of adjusting the sense current can be performed, if desired, by selecting or deselecting the trim FET to force the current as close as possible to the desired current by programmable means. This method can be used in an environment where the gain of the driver circuit is variable.
[0015]
Another general feature of the present invention is that it provides a circuit that can be connected to operate a voice coil that positions the head of a disk drive system. The circuit includes a driver circuit that controls the current flowing through the voice coil and at least one sense current circuit that may include a FET device for sensing and controlling the current in the respective current path of the driver circuit. A programmable circuit is connected to adjust at least one of the sense current circuits and controls the current through the voice coil that positions the head to a desired position.
[0016]
Trimming capability includes, for example, one or more trim FETs that can be selectively connected in parallel to a current sensing FET, which can be an FET connected to mirror one current in the current path of the driver circuit. Realized by providing. Such selective connection allows the effective channel width that the FET device produces to be selectively obtained so that the current of the voice coil, and thus the position of the head controlled by the voice coil, can be adjusted.
[0017]
Yet another general feature of the present invention is the provision of a driver circuit that provides a drive signal to a voice coil that positions the head of a disk drive system. The driver circuit includes first and second current paths, each connected between a supply voltage and a reference potential. Each current path has two driver transistors, and a voice coil can be connected between these driver transistors in each current path. At least one sensing transistor is connected to generate a mirror current that mirrors with the current of the associated driver transistor. A circuit responsive to the sensing transistor mirror current is provided to control the amplitude of the current of the associated driver transistor in each current path. At least one trim transistor is connected in parallel to each one of the sensing transistors and provided with a programmable circuit connected to selectively activate at least one trim transistor, the at least one trim transistor The sensing transistor to which the transistor is associated adjusts the amplitude of the current that mirrors the associated current path.
[0018]
Another general feature of the present invention is that it provides a disk drive system. The disk drive system includes a rotating data medium that can be a magnetic floppy disk, magnetic hard disk, CD-ROM, or the like. At least one head is selectively positionable for reading at least data from the rotating data medium, and a voice coil is arranged for positioning the head in response to the current of the voice coil. The first and second current paths are each connected between a supply voltage and a reference potential. Each current path includes two driver transistors, and a node between each of these driver transistors in each current path is connected to a respective end of the voice coil. A plurality of sensing transistors are respectively connected to generate a mirror current, and the mirror current mirrors with a mirroring current of an associated driver transistor in each current path, and responds to the mirror current of the sensing transistor. Circuitry controls the amplitude of the current of the associated driver transistor in each current path. At least one trim transistor is connected in parallel to each one of the sensing transistors, and a programmable circuit is connected to selectively activate at least one trim transistor, and at least one trim transistor is associated The sensing transistor that adjusts the amplitude of the current that mirrors the associated current path.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is illustrated in the accompanying drawings, wherein like reference numerals are used to refer to like or similar parts throughout the various views of the drawings.
Referring now to FIG. 1, an electrical schematic diagram 10 of the portion of the voice coil driver circuit 12 that positions the read / write head 13 of the disk drive system 14 is shown. Although the illustrated disk drive system 14 is of the type typically used in connection with hard disk drives, the present invention is not limited to other disk drive systems, CD-ROM systems, and the like. It should be understood that the same applies to a type of disk drive system.
[0020]
The illustrated disk drive system 14 includes a rotating media 16, which can be, for example, a rotating platter having a magnetic media formed thereon. The rotating medium 16 can be rotated by a three-phase, multi-phase, DC motor system (not shown) controlled by a disk control circuit 18.
[0021]
The head 13 is moved to a selected position along the radius of the rotating medium 16 by the control arm 18, and is similarly moved in the lateral direction by the current supplied to the voice coil 20. Data written to or read from the rotating media 16 by the head 13 is controlled by a data circuit 22 that is controlled by an associated computer not shown. The disk drive assembly, in particular the voice coil 20, can be provided away from the driver circuit 12 to which it is connected.
[0022]
The driver circuit 12 shown is of the type commonly known as an “H” bridge and has two current paths on each side of the “H” bridge, shown as side “A” and side “B”. including. In the illustrated embodiment, each side is V _CC Having a respective high side driver transistor 30 and 32 and a respective low side driver transistor 34 and 36 connected between and ground. The gates of the driver transistors 30 to 36 are connected to drive amplifiers 40 and 42 and controlled by a signal from a voice coil control signal source 44. Since the voice coil control signal from the voice coil control signal source 44 is connected in reverse to the amplifiers 40 and 42, the respective driver transistors 30 to 36 are driven in reverse. In this way, the difference between the currents in the opposite current paths 26 and 28 where the nodes 46 and 48 to which the voice coil 20 is connected exists is the current supplied to the voice coil 20 that positions the head 13. To express.
[0023]
Trimmable feedback control circuit 50 is connected between current path 26 and voice coil control signal source 44 and controls the signals supplied to driver amplifiers 40 and 42. The trimmable feedback control circuit 50 serves to generate a feedback current proportional to the drive current of the current path 26 on the side A of the driver circuit 12. The feedback current generated by the trimmable feedback control circuit 50 has a function of canceling the voice coil control signal when the head 13 is at a desired position. Ideally, the current of the voice coil 20 is reduced to 0 (or other value). To a desired quiescent current value).
[0024]
With further reference now to FIG. 2, an exemplary circuit 60 utilizing the trimmable feedback control circuit 50 described above is shown. The circuit 60 supplies a drive signal to the voice coil 20 in accordance with a digital drive signal 62 at the input of this circuit.
[0025]
More specifically, the digital input signal 62 is converted into an analog signal by a digital / analog converter 64, and the analog signal is filtered by a notch filter 66. The output from the notch filter 66 is modified by the output from the feedback control circuit 50 (the portion away from the general circuit shown is contained within the dotted portion of the box 50), and the driver amplifier 40 and 42 input. The outputs of driver amplifiers 40 and 42 are supplied to driver transistor circuits 68 and 70, respectively, on sides A and B of the “H” bridge driver circuit, as shown in FIG. 1 above.
[0026]
The output from the driver transistor circuit 68 is obtained from a mirror circuit, which will be described later, and is supplied to the trimmable feedback control circuit 50. The output generated by the feedback control circuit 50 is subtracted from the control signal that is the output of the notch filter 66. The As mentioned above, the purpose of the feedback circuit is to generate a signal that forces the voice coil current to zero in the rest state.
[0027]
Also shown in circuit 60 of FIG. 2 is an optional digital offset control input signal 74 and an optional gain range control input signal 76. The digital offset control input signal 74 is converted into an analog signal by the digital / analog converter 75 and gives a controllable voltage offset value to the drive signal supplied to the voice coil 20, and the gain range control circuit will be described in detail below. Thus, the gain range of the feedback control circuit 50 is changed. If a digital offset control input signal 74 and a gain range control input signal 76 are used, the output from the DAC 75 can be appropriately attenuated by the attenuator 80 according to the range specified by the range control signal 76. The appropriately attenuated offset signal is added to the output from the digital VCM control DAC 64 in the adder 82 and then input to the notch filter 66.
[0028]
Details of the current sensing circuit will now be shown by further reference to the current sensing circuit 90 of FIG. The portion of the driver circuit shown in FIG. 3 corresponds to the portion of side A in FIG. 1 and mirrors the current in the current path 26 above and below the node 46. (mirror) A circuit 92 is shown. More specifically, mirror circuit 92 includes mirror transistors 96 and 98 having drains and gates connected to the drains and gates of high and low side driver transistors 30 and 34, respectively. The source of the high side driver transistor 30 is connected to the source of the mirror transistor 96 by the amplifier 100. Similarly, the source of the low side driver transistor 34 is connected to the source of the mirror transistor 98 by the amplifier 102. The width to length ratio of driver transistors 30 and 34 is about 20,000: 0.8, and the width to length ratio of mirror transistors 96 and 98 is about 10: 0.8.
[0029]
As shown, optional gain range control circuits 104 and 108 are connected between the gates of high and low side driver transistors 30 and 34 and the gates of their respective current mirror transistors 96 and 98. ing. Gain range control circuits 104 and 108 receive a gain range control signal 76 as described above and are a series of FETs that can be selectively connected in parallel to respective mirror transistors 96 and 98, for example, according to the value of gain range control signal 76. A device (not shown) may be included.
[0030]
Flows through high-side and low-side mirror transistors 96 and 98, respectively, i _HSSA And i _LSSA Is further mirrored into the mirror circuit 110. More specifically, two transistors 112 and 114 are connected to V _CC And low-side mirror transistor 98 are connected in series, through which the same current i _LSSA Flows. The drains and gates of transistors 112 and 114 are interconnected. Similarly, two transistors 116 and 118 are connected in series between ground and high-side mirror transistor 96 through which the same current i _HSSA Flows. The drains and gates of transistors 116 and 118 are also interconnected, respectively.
[0031]
Mirror transistors 120 and 122 are connected to mirror the currents of respective transistors 112 and 114, and similarly, mirror transistors 124 and 126 are mirrored with the currents of respective transistors 116 and 118. It is connected. It can be seen that the current flowing through the current path 130 including the transistors 120, 122, 124 and 126 is a proportional value close to the current difference on each side of the node 46 connected to the voice coil 20. The current value in current path 130 is determined by the current i flowing through the voice coil when using appropriate transistor sizing. _COIL Can be approximately equal to / 2000. The current on output line 134 provides a feedback current that is fed back to control the current in voice coil 20, as described above in connection with FIG.
[0032]
Trim networks 140 and 142 are provided to further control the value of the feedback current that would otherwise fluctuate due to large size differences, manufacturing tolerances, and other factors between the mirror transistor and the driver transistor, The current flowing through each mirror transistor 120 and 126 is controlled and varied. Trim networks 140 and 142 are shown in detail in FIG. 4 and will now be referenced.
[0033]
Specifically, trim networks 140 and 142 according to embodiments of the present invention include a number of FET transistors that can be selectively connected in parallel to respective low-side mirror transistor 120 and high-side mirror transistor 126. Trim network 140 includes, for example, four transistors 145-148, each connected with its source connected to the source of mirror transistor 120 and its drain connected to the drain of mirror transistor 120. The gates of transistors 145-148 can be selectively connected to the gate of mirror transistor 120 by respective switches 150-153 controlled by a programmable device, such as the illustrated EEPROM 170.
[0034]
Trim network 142 includes four transistors 155-158, each connected with its source connected to the source of mirror transistor 126 and its drain connected to the drain of mirror transistor 126. The gates of transistors 155-158 can be selectively connected to the gate of mirror transistor 126 by respective switches 160-163, also controlled by EEPROM 170.
[0035]
As described above, FET devices 120 and 122 are controlled by the programmed output of EEPROM circuit 170. The effective channel width of the mirror devices 120 and 126 is thus controlled by the EEPROM 170, which can be configured on the same chip as the rest of the sense and trim circuitry. Normally, the EEPROM 170 is configured in a factory or manufacturing site. However, it can be programmable by the user if desired. It will be appreciated that the functions performed by the EEPROM 170 may also be performed by other programmable circuits, such as programmable fuse devices, programmable gate devices, and the like.
[0036]
The adjustable FET devices 120 and 126 can have a plurality of differently sized FET devices that can be selectively and individually connected in parallel. It should be noted that any number of devices can be used, depending on the sense current regulation application and resolution required or desired. The present invention is intended to force the voice coil 20 current to zero or some other predetermined value, but by selective switching of one or more transistors to parallel circuits 140 and 142. It should also be noted that discontinuous trimming necessarily provides a quantized stage in circuit trimming. Therefore, the number of transistors that can be connected by switching controls the resolution for equalizing the current. In the illustrated embodiment, for example, FET devices 145 to 148 and 155 to 158 may have respective sizes of 1/1, 1/2, 1/4, and 1/8. (The ratio shown represents the width-to-length ratio of the FET device.) This gives a trim range of ± 10% with a step size of ± 1%.
[0037]
Thus, depending on the programmable state appearing on the output terminal of the EEPROM 170, selected ones of the FET devices 145 to 148, and 155 to 158, together with the FET devices 120 and 126 that are not selectively controlled by the EEPROM 170. Turned on. Note that in the normal or default state, one or more of the FET devices 145-148 and 155-158 are typically turned on, allowing the flexibility to obtain reduced current carrying capability from the normal state. Should. In this way, for example, FET devices 148 and 158 can be in a default or initially on state, which is typically essentially in parallel with mirror transistors 120 and 126. In this way, if a smaller feedback current 134 is desired, FETs 148 and 158 may be turned off and only FET mirror transistors 120 and 126 remain turned on. Alternatively, if a larger feedback current 134 is desired, one or more of the remaining FET transistors 145-147 and 155-157 may be turned on as needed.
[0038]
Although the present invention has been described and illustrated in some detail, the disclosure has been made with respect to examples only and, according to one of ordinary skill in the art, from the spirit and scope of the invention as defined by the claims. It should be understood that various changes can be made in the combination and arrangement of parts without departing.
[0039]
The following items are further disclosed with respect to the above description.
(1) A method of supplying a drive current to a voice coil for positioning a head of a disk drive,
Measuring a first current supplied to the voice coil;
Mirroring the first current and providing a sense current proportional to the first current;
Modifying the magnitude of the first current in a feedback circuit using the sense current to position the head near a desired position;
Adjusting the sense current to be more precisely equal to a desired magnitude and positioning the head closer to the desired position;
Said method.
[0040]
(2) the step of adjusting the sense current includes selectively connecting at least one active device having a current path in parallel with the active device connected to mirror the current of the power transistor; The method according to claim 1.
[0041]
(3) the step of selectively connecting at least one active device having a current path in parallel with the active device connected to mirror the current of the power transistor, wherein the step of: 3. The method of claim 2, comprising selectively connecting a trim FET having a parallel to a current mirror FET having a second channel width to length ratio.
[0042]
(4) The step of adjusting the sense current includes programmably connecting at least one active device having a current path in parallel with the active device connected to mirror the current of the power transistor. The method according to claim 1.
[0043]
(5) the step of programmably connecting at least one active device having a current path in parallel with the active device connected to mirror the current of the power transistor, wherein the first channel width to length ratio is 5. The method of claim 4, comprising programmably connecting at least one trim FET having a parallel to a current mirror FET having a second channel width to length ratio.
(6) The method according to the first item, further including a step of changing a gain of the feedback circuit.
[0044]
(7) a circuit that can be connected to operate a voice coil that positions the head of the disk drive system,
A driver circuit for controlling a current flowing through the voice coil;
A plurality of sense current circuits for detecting and controlling the current in each of the current paths;
A programmable circuit connected to regulate at least one of the sense current circuits and controlling a current flowing through the voice coil to position the head in a desired position;
Including the circuit.
[0045]
(8) The circuit according to item 7, wherein the sense current circuit includes an FET device.
9. The circuit of claim 8, wherein the FET devices are connected in parallel and the programmable circuit programmably selects the FET device to control the effective channel width provided by the FET device.
[0046]
(10) The FET device is connected in parallel by selectively connecting a trim FET having a first channel width to length ratio in parallel with a current mirror FET having a second channel width to length ratio. 9. The circuit of claim 8, wherein the programmable circuit programmably selects the FET device to control an effective channel width provided by the FET device.
[0047]
(11) In a driver circuit for supplying a drive signal to a voice coil for positioning a head of a disk drive system,
First and second current paths, each connected between a supply voltage and a reference potential, each current path including two driver transistors, wherein the voice coils are connected in respective current paths; The first and second current paths connectable between the driver transistors;
A plurality of sensing transistors, each sensing transistor being connected to generate a mirror current that mirrors a mirrored current of an associated driver transistor in a respective current path; A sensing transistor;
In response to the mirror current of the sensing transistor, a circuit that controls the amplitude of the current of the associated driver transistor in a respective current path, and at least one trim transistor is connected to each one of the sensing transistors. Said at least one trim transistor connected in parallel to one another;
The at least one trim transistor is selectively activated to connect the sensing transistor to which the at least one trim transistor is associated to adjust the amplitude of the mirrored current in the associated current path. Programmable circuit,
Including the driver circuit.
[0048]
(12) The driver circuit according to item 11, wherein the sensing transistor and the trim transistor are FET devices.
(13) The driver circuit according to the eleventh aspect, wherein the first and second current paths are connected to the voice coil in an “H” bridge configuration.
[0049]
(14) a rotary data medium;
At least one head that is selectively positionable for reading at least data from the rotating data medium;
The voice coil for positioning the head in response to the current of the voice coil;
First and second current paths each connected between a supply voltage and a reference potential, each current path including two driver transistors, each of the driver transistors in the current path being The first and second current paths, each having a node connected to a respective end of the voice coil;
Each of the plurality of sensing transistors is connected to produce a mirror current, the mirror current mirroring a mirrored current of an associated driver transistor in the respective current path. When,
A circuit for controlling an amplitude of the current of the associated driver transistor in a respective current path in response to the mirror current of the sensing transistor;
At least one trim transistor connected in parallel to each one of the sensing transistors;
Programmable to selectively activate the at least one trim transistor and to adjust the amplitude of the mirrored current of the current path to which the sensing transistor with which the at least one trim transistor is associated is associated The circuit and
Including hard disk drive system.
[0050]
(15) The hard disk drive system according to item 14, wherein the sensing transistor and the trim transistor are FET devices.
(16) The hard disk drive system according to (14), wherein the plurality of current paths are connected to the voice coil in an “H” configuration.
[0051]
(17) A circuit 12 and a method for supplying a drive current to the voice coil 20 for positioning the head 13 of the disk drive 14 include a driver circuit 68 and 70 for controlling a current flowing through the voice coil 20, and a current path 26 of the driver circuit 12. And at least one sense current circuit 92, which may include FET devices 112, 114, 116, 118 for sensing and controlling the current of the current. A programmable circuit 170 is connected to adjust at least one of the sense current circuits 112, 114, or 116, 118 to control the current through the voice coil 20 that positions the head 13 to a desired position. The trim capability may be selectively connected in parallel to current mirror FETs 120, 126, which may be, for example, FETs connected to mirror one of the current paths 26 of the driver circuit 12. This is realized by providing further trim FETs 145 to 148 and 155 to 158. Such selective connection selectively provides the effective channel width that the FET devices 120, 145 to 148, or 126, 155 to 158 are produced, so that the current of the voice coil 20 and hence the voice coil 20 is controlled. The position of the head 13 can be adjusted.
[Brief description of the drawings]
FIG. 1 is an electrical schematic diagram of a portion of a disk drive system incorporating a trimmable current sensing circuit for controlling a voice coil head positioning current in the disk drive system, according to an embodiment of the present invention.
2 is an electrical schematic diagram of an exemplary configuration of a trim circuit of the type used in the disk drive system of FIG. 1, in accordance with an embodiment of the present invention.
3 is an electrical schematic diagram of a configuration of a trim circuit and a typical FET mirror circuit of the type used in the disk drive system of FIG. 2, in accordance with an embodiment of the present invention.
4 is an electrical schematic diagram of a trim circuit shared with the FET mirror circuit of FIG. 3, in accordance with an embodiment of the present invention.
[Explanation of symbols]
12 Voice coil driver circuit
13 Read / write head
14 Disk drive system
20 Voice coil
26 Current path
68 Driver transistor circuit
70 Driver transistor circuit
92 Current mirror circuit
112 transistor
114 transistor
116 transistor
118 transistor
170 EEPROM

Claims (2)

A circuit connected to operate a voice coil for positioning a head of a disk drive system,
A driver circuit for controlling a first current path in a first current path and a second current path in a second current path flowing in the voice coil;
A plurality of sense current circuits for detecting and controlling the first current in the first current path and the second current in the second current path ;
A programmable circuit connected to regulate at least one of the sense current circuits, the programmable circuit controlling a current flowing in the voice coil to position the head in a desired position; ,
Only including,
The sense current circuit includes a plurality of FET devices;
Each of the FET devices is connected in parallel,
The programmable circuit programmatically selects the FET device to control the effective channel width provided by the FET device.
A circuit connected to operate the voice coil. A circuit connected to operate a voice coil for positioning a head of a disk drive system,
A driver circuit for controlling a first current path in a first current path and a second current path in a second current path flowing in the voice coil;
A plurality of sense current circuits for detecting and controlling the first current in the first current path and the second current in the second current path ;
A programmable circuit connected to regulate at least one of the sense current circuits, the programmable circuit controlling a current flowing in the voice coil to position the head in a desired position; ,
Only including,
The sense current circuit includes a plurality of FET devices;
Each of the FET devices is connected in parallel,
The programmable circuit programmatically connects the FET device by selectively connecting a trim FET having a first channel width to length ratio in parallel with an FET having a second channel width to length ratio. Select to control the effective channel width provided by the FET device;
A circuit connected to operate the voice coil.

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