WO2015164445A1

WO2015164445A1 - Apparatus and method for controlling current in a device due to electrostatic discharge or surge event

Info

Publication number: WO2015164445A1
Application number: PCT/US2015/026980
Authority: WO
Inventors: Marc ZIEMS
Original assignee: Thomson Licensing
Priority date: 2014-04-22
Filing date: 2015-04-22
Publication date: 2015-10-29
Also published as: TW201603648A

Abstract

Described is an apparatus and method for controlling current in a printed circuit board due to a surge or electrostatic discharge. The apparatus (300) includes a first interface (320, 325, 330, 370) providing a first signal to a main control circuit (305), a radio frequency connector (340) providing a second signal received from a broadcast signal source to the main control circuit (305), and a ground connection (360) on a printed circuit board connecting a ground point at the first interface (320, 325, 330, 370) to a ground point at the connector (340) used for controlling current induced at the first interface (320, 325, 330, 370) such that the current does not affect operation of the main control circuit (305). The method includes inducing (420) a current into a printed circuit board as a result of an event, and providing (430) a conductive path for the current from a ground at the induction point to a ground point at a connector such that the current does not affect operation of a circuit connected on the printed circuit board.

Description

APPARATUS AND METHOD FOR CONTROLLING CURRENT IN A DEVICE DUE TO AN ELECTROSTATIC DISCHARGE OR SURGE EVENT

CROSS-REFERENCE TO RELATED APPLICATION This application claims the benefit of U.S. Provisional Application Serial

No. 61 /982,388, filed April 22, 2014, which is incorporated by reference herein in its entirety.

TECHNICAL FIELD OF THE INVENTION The present disclosure generally relates to an electronic device that is capable of receiving signals. More particularly, the present disclosure is related to a communication apparatus that includes a grounding mechanism that controls current induced into the apparatus due to a surge or electrostatic discharge (ESD) event.

BACKGROUND OF THE INVENTION

This section is intended to introduce the reader to various aspects of art, which may be related to the present embodiments that are described below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light. Many home entertainment devices not only include the capability to communicate with other devices in a home network but also include the ability to receive and/or process available media content from a plurality of sources, including a plurality of providers. The sources and providers may include, but are not limited to, satellite service, cable service, and free to home over the air terrestrial service. The services may operate in the same or different frequency ranges and may use the same or different transmission formats or protocols. The devices for receiving the services often include, but are not limited to, set-top boxes, gateways, televisions, home computers, and the like. Further, many of these devices may include multiple interfaces for different types of externally provided services as well as different types of home networks. These devices may also include additional features internal to the device, such as storage elements, hard drives, compact disk or digital versatile disk drives, and the like.

These entertainment devices are often subjected to electrostatic discharge (ESD) or other surge current events that are created by the environment around the device. For example, a user may touch a button or a universal serial bus (USB) connector on the entertainment device after building up a static body charge produced an ESD event. The high ESD current conduct through the grounded shell on the button or connector into the ground plane of the printed circuit board in the entertainment device as the current seeks an exit point from the device to an earth ground. The high current causes a potential difference in voltage across the ground plane which can disturb circuitry in the entertainment device. For example, the potential difference across the ground plane may cause the processor to reset or go into a lock-up state or may cause portions of a memory to change state. In a worst case scenario, the electronic circuits in the entertainment device may suffer actual structural damage. As a result, the effects described above from ESD and/or surge current may temporarily or permanently affect the operation of the entertainment device.

Several techniques have been developed in order to mitigate or reduce the effect of ESD and other surge current in devices, such as entertainment devices. One technique involves grounding the shell of a button or connector to a metal chassis or other structural metal used in the entertainment device. The additional ground structure lowers the amount of current conducted through ground plane of the printed circuit board and reduces the potential voltage difference. A further improvement occurs by assuring that an earth ground is connected to metal chassis or structural metal in the device.

However, the technique of grounding to a metal case or other metal structure in the device is often not practical because many modern entertainment devices do not use a metal chassis or structural metal in order to reduce cost and weight. Further many of these entertainment devices do not include an earth ground as part of the power source connection to the device. Therefore, there is a need for an improved ground structure for controlling ground currents from ESD or surge events thereby reducing the effects of the ground currents on circuits in a device, such as an entertainment device.

SUMMARY

According to an aspect of the present disclosure, an apparatus is described. The apparatus includes a first interface, the first interface providing a first signal to a main control circuit, the signal being at least one of a data signal and a control signal, a radio frequency connector, the radio frequency connector providing a second signal received from a broadcast signal source to the main control circuit, and a ground connection on a printed circuit board, the ground connection conductively connecting a ground point at the first interface to a ground point at the radio frequency connector, the ground connection used for controlling unwanted current induced at the first interface such that the unwanted current does not affect an operation of the main control circuit.

According to another aspect of the present disclosure, a method is described. The method includes inducing an unwanted current into a printed circuit board of a device, and providing a conductive path for the unwanted current on the printed circuit board from a ground at an ingress point for the unwanted current to a ground point at a radio frequency connector such that the unwanted current does not affect an operation of a circuit connected on the printed circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

These, and other aspects, features and advantages of the present disclosure will be described or become apparent from the following detailed description of the preferred embodiments, which is to be read in connection with the accompanying drawings.

FIG. 1 is a block diagram of an exemplary system for receiving broadcast media content in accordance with the present disclosure;

FIG. 2 is a diagram of an exemplary circuit including a ground structure in a device in accordance with the present disclosure;

FIG. 3 is another exemplary circuit including a ground structure in a device in accordance with the present disclosure; and

FIG. 4 is a flow chart of an exemplary process for controlling ground currents in a device caused by ESD or surge events in accordance with the present disclosure.

It should be understood that the drawing(s) are for purposes of illustrating the concepts of the disclosure and is not necessarily the only possible configuration for illustrating the disclosure. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

It should be understood that the elements shown in the figures may be implemented in various forms of hardware, software or combinations thereof. Preferably, these elements are implemented in a combination of hardware and software on one or more appropriately programmed general-purpose devices, which may include a processor, memory and input/output interfaces. Herein, the phrase "coupled" is defined to mean directly connected to or indirectly connected with through one or more intermediate components. Such intermediate components may include both hardware and software based components.

The present description illustrates the principles of the present disclosure. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the disclosure and are included within its scope. All examples and conditional language recited herein are intended for educational purposes to aid the reader in understanding the principles of the disclosure and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions.

Moreover, all statements herein reciting principles, aspects, and embodiments of the disclosure, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure.

Thus, for example, it will be appreciated by those skilled in the art that the block diagrams presented herein represent conceptual views of illustrative circuitry embodying the principles of the disclosure. Similarly, it will be appreciated that any flow charts, flow diagrams, state transition diagrams, pseudocode, and the like represent various processes which may be substantially represented in computer readable media and so executed by a computer or processor, whether or not such computer or processor is explicitly shown.

The functions of the various elements shown in the figures may be provided through the use of dedicated hardware as well as hardware capable of executing software in association with appropriate software. When provided by a processor, the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared. Moreover, explicit use of the term "processor" or "controller" should not be construed to refer exclusively to hardware capable of executing software, and may implicitly include, without limitation, digital signal processor (DSP) hardware, read only memory (ROM) for storing software, random access memory (RAM), and nonvolatile storage.

Other hardware, conventional and/or custom, may also be included. Similarly, any switches shown in the figures are conceptual only. Their function may be carried out through the operation of program logic, through dedicated logic, through the interaction of program control and dedicated logic, or even manually, the particular technique being selectable by the implementer as more specifically understood from the context.

In the claims hereof, any element expressed as a means for performing a specified function is intended to encompass any way of performing that function including, for example, a) a combination of circuit elements that performs that function or b) software in any form, including, therefore, firmware, microcode or the like, combined with appropriate circuitry for executing that software to perform the function. The disclosure as defined by such claims resides in the fact that the functionalities provided by the various recited means are combined and brought together in the manner which the claims call for. It is thus regarded that any means that can provide those functionalities are equivalent to those shown herein.

The present disclosure is directed at problems associated with controlling ground current caused by an ESD or surge event in a device, such as an entertainment device or signal receiver. The presence of the charge or event induced current is caused by, for example, the user generating a static charge and touching a button on the device. The charge or event induced current is undesirable or unwanted in the ground plane and may affect the operation of the circuits in the device. A typical ground structure involves making ground connections between elements or components on the printed circuit board in the shortest and closest manner of routing. Alternatively, a solid ground plane as part of a multi-layer printed circuit board may be used as an interconnection. However, these ground structures allows the ground current due to the surge or ESD event to pass through the components or allow the components to operate at different relative voltage potentials with respect to ground due to the presence in ground current. The effects may include, but are not limited to, causing an automatic reset in one or more of the electronic components in the device or altering a state of a portion or all of a memory. The device may appear to lock up or freeze in operation requiring the user to unplug or otherwise manually reset the device.

The present embodiments describe an apparatus and method for controlling current due to ESD or other surge events in a device. In particular, the embodiments describe a grounding mechanism for controlling this current within a ground plane in a printed circuit board in the device. The mechanism provides a separate electrical path for high currents due to ESD and surge events from external sources that allows the current to conduct to the lowest potential ground connection available for the printed circuit board as well as the device. The separate path may also be lower in resistance or impedance to the ground current than the other remaining ground structure. The mechanism greatly diminishes the possibility of the current disrupting normal electronic circuit operations, such as resetting or locking-up the device.

One or more of the embodiments described below is directed at mechanisms that control ESD or surge current that enters the ground system of a device and provides an exit path for the current from the device. The mechanisms prevent the current from entering and damaging critical circuits in the device. Many products operate such that the best ground path to/from the device cannot utilize the power supply system. The power supply may include an isolated external power supply circuit or may lack a third wire ground in the connection to the main power connection. In this case, a secondary ground path becomes the ingress/egress point for the ESD or surge current. In a set top box, such as a set top box connected to a satellite signal receiving system, the lowest potential earth ground point is the RF input connector. ESD or surge current that enters the product on a front panel (e.g., through a button or other opening/entry) may seek the RF input connector ground by passing through the other components in the device. The ingress point for the ESD or surge event may be the grounded shell or shield of a connector, the ground connection of an ESD protection diode, an externally accessible push button switch, a light element (e.g., light emitting diode), or any electrical connection that may conduct current from an external ESD or surge event. The present disclosure steers the current by providing a separated ground path from the front panel assembly to the RF input connector. Further, a grounded conductive surface area in the printed circuit board at the front panel area most prone to ESD or surge event current ingress may be exposed by removing the solder resist mask material. The exposed conductive area, along with any other conductive shielding used around components in the device may promote the induction of ESD or surge energy to enter the ground at that point.

Described herein are mechanisms for controlling current in a signal receiving device caused by ESD or surge events. In particular, the mechanisms describe a grounding structure that utilizes an F-connector as an earth ground point for current egress in the device. It is important to note that the mechanisms may be adapted for use with other connectors used for signal connection by those skilled in the art. Further, the mechanisms may also be easily adapted with other devices by those skilled artisans, including devices that may not include an input signal connection. For instance, with only minor modifications, the embodiments described below could be modified to work with a device that connects to a television through a high definition multimedia interface (HDMI) connector. The television then may provide an earth ground connection through an interface in the power supply in the television to the main power source.

Turning now to the drawings and referring initially to FIG. 1 , an exemplary embodiment of a system 100 for receiving signals using aspects of the present invention is shown. System 100 primarily receives signals from one or more satellites as well as multiple television broadcast transmission sites. The signals are provided by one or more service providers and represent broadcast audio and video programs and content. System 100 is described as including components that reside both inside and outside a user's premises. It is important to note that one or more components in system 100 may be moved from inside to outside the premises. Further, one or more components may be integrated with a display device, such as a television or display monitor (not shown). In either case, several components and interconnections necessary for complete operation of system 100 are not shown in the interest of conciseness, as the components not shown are well known to those skilled in the art.

An outdoor unit (ODU) 101 receives signals from satellites and from terrestrial transmission towers through an over the air and/or near earth orbit communications link. ODU 101 is connected to set top box 102. Within set top box 102, the input is connected to filter 103. Filter 103 connects to three signal processing paths. A first path includes tuner 105, link circuit 106, and transport decoder 108 connected together serially. A second path includes tuner 1 10, link circuit 1 12, and transport decoder 1 14 connected together serially. A third path includes MoCA circuit 134 which further connects to controller 1 16. The outputs of transport decoder 108 and transport decoder 1 14 each connect to controller 1 16. Controller 1 16 connects to security interface 1 18, external communication interface 120, user panel 122, remote control receiver 124, audio/video output 126, power supply 128, memory 130, and ODU control 132. External communication interface 120, remote control receiver 124, audio/video output 126, and power supply 128 provide external interfaces for the set top box 102. ODU control 132 also connects to the filter 103. Satellite signal streams, each containing a plurality of channels, are received by ODU 101 . ODU 101 includes a dish for capturing and focusing the propagated radio wave from the atmosphere onto one or more antennas contained within a structure known as a low noise block converter (LNB). ODU 101 may be configured to receive the signal streams from satellite transponders located on one or more satellites. In a preferred embodiment, two sets of sixteen channels are received by ODU 101 , and converted, using one or more LNBs to a frequency range of 950 Megahertz (MHz) to 2,150 MHz, referred to as L-band. ODU 101 also includes a terrestrial antenna for receiving over the air broadcasts. In a preferred embodiment, ODU 101 includes a multiple element antenna array for receiving ISDBT signals in the frequency range from 170 MHz to 800 MHz.

ODU 101 provides a converted signal stream to the set top box 102 through radio frequency (RF) co-axial cable. The converted signal stream is provided to filter 103. In a preferred embodiment, filter 103 operates as a multiplex filter with up to three separate filter sections or interfaces. The frequency response properties of filter 103 may include a separate highpass filter and lowpass filter such that the frequency passbands of each do not overlap. The arrangement, often referred to as a diplexer or diplex filter, allows for a separation, through signal filtering, of the incoming satellite signal and/or MoCA signal from the terrestrial signal and/or MoCA signal. In a preferred embodiment, the low pass filter frequency response pass band ends at a frequency below 900 MHz. The low pass filter portion allows a MoCA signal in a frequency range from 475 MHz to 625 MHz as well as a terrestrial signal in the frequency range from 170 MHz to 800 MHz to pass through to subsequent blocks while attenuating, or not passing through, a satellite signal in a frequency range from 950 MHz to 2,150 MHz. The high pass filter portion operates in an opposite manner passing the MoCA signal, in the frequency range around 1 100 MHz, along with the satellite signal through and attenuating cable or terrestrial broadcast signal. The high pass filter portion may also filter any electrical supply or communication signals provided to the ODU 101 . An additional bandpass filter circuit may be provided to further process MoCA signals and provide the signals as an output to a home MoCA network or for processing in set top box 102. Filter 103 may also include surge or transient voltage protection devices.

The output signal from the high pass filter portion of filter 103 is provided to a first signal path containing a tuner 105, a link circuit 106, and a transport decoder 108 connected in a serial fashion. The output signal from the low pass filter portion of the filter 103 is provided to a second signal path. The second signal path also contains a tuner 1 10, a link circuit 1 12, and a transport decoder 1 14 connected in a serial fashion. Each processing path may perform similar processing on the filtered signal streams, the processing being specific to the transmission protocol used.

Tuner 105 processes the split signal stream by selecting or tuning one of the channels provided from a satellite service provider in the highpass filtered signal stream to produce one or more baseband signals. Tuner 105 contains circuits (e.g., amplifiers, filters, mixers, and oscillators) for amplifying, filtering and frequency converting the satellite signal stream. Tuner 105 typically is controlled or adjusted by link circuit 106. Alternately, tuner 105 may be controlled by another controller, such as controller 1 16, which will be described later. The control commands include commands for changing the frequency of an oscillator used with a mixer in tuner 105 to perform the frequency conversion.

Tuner 1 10 processes the lowpass filtered signal stream by selecting or tuning one of the terrestrial or cable broadcast channels in the split signal stream to produce one or more baseband signals. Tuner 1 10 contains circuits (e.g., amplifiers, filters, mixers, and oscillators) for amplifying, filtering and frequency converting the signal stream. Tuner 1 10 may controlled or adjusted in a manner similar to that described earlier for tuner 105.

Typically the baseband signals at the output of tuner 105 or tuner 1 10 may collectively be referred to as the desired received signal and represent one satellite, terrestrial, and/or cable channel selected out of a group of channels that were received as the input signal stream. Although the signal is described as a baseband signal, this signal may actually be positioned at a frequency that is only near to baseband.

The one or more baseband signals originating from the satellite service provider are provided to link circuit 106 through tuner 105. Link circuit 106 typically contains the processing circuits needed to convert the one or more baseband signals into a digital signal for demodulation by the remaining circuitry of link circuit 106. In one embodiment the digital signal may represent a digital version of the one or more baseband signals. In another embodiment the digital signal may represent the vector form of the one or more baseband signals. Link circuit 106 also demodulates and performs error correction on the digital signal from the satellite service provider to produce a transport signal. The transport signal may represent a data stream for one program, often referred to as a single program transport streams (SPTS), or it may represent multiple program streams multiplexed together, referred to as a multiple program transport stream (MPTS).

The one or more baseband signals originating from the broadcast service provider are provided to link circuit 1 12 through tuner 1 10. Link circuit 1 12 typically contains the processing circuits needed to convert the one or more baseband signals into a digital signal for demodulation by the remaining circuitry of link circuit 1 12 in a manner similar to link circuit 106 described earlier. Link circuit 1 12 also demodulates, performs broadcast channel equalization error correction on the digital signal from the broadcast service provider to produce a transport signal. As described earlier, the transport signal may represent a data stream for one program or it may represent multiple program streams multiplexed together.

The transport signal from link circuit 106 is provided to transport decoder 108. Transport decoder 108 typically separates the transport signal, which is provided as either a SPTS or MPTS, into individual program streams and control signals. Transport decoder 108 also decodes the program streams, and creates audio and video signals from these decoded program streams. In one embodiment, transport decoder 108 is directed by user inputs or through a controller such as controller 1 16 to decode only the one program stream that has been selected by a user and create only one audio and video signal corresponding to this one decoded program stream. In another embodiment, transport decoder 108 may be directed to decode all of the available program streams and then create one more audio and video signals depending on user request.

The transport signal from link circuit 1 12 is similarly provided to transport decoder 1 14. Transport decoder 1 14 decodes the program streams, and creates audio and video signals from these decoded program streams as directed by user inputs or a controller in a manner similar to that described earlier for transport decoder 108. The audio and video signals, along with any necessary control signals, from both transport decoder 108 and transport decoder 1 14 are provided to controller 1 16. Controller 1 16 manages the routing and interfacing of the audio, video, and control signals and, further, controls various functions within set top box 102. For example, the audio and video signals from transport decoder 108 may be routed through controller 1 16 to an audio/video (A/V) output 126. A/V output 126 supplies the audio and video signals from set top box 102 for use by external devices (e.g., televisions, display monitors, and computers). Also, the audio and video signals from transport decoder 1 14 may be routed through controller 1 16 to memory block 130 for recording and storage.

Memory block 130 may contain several forms of memory including one or more large capacity integrated electronic memories, such as static random access memory (SRAM), dynamic RAM (DRAM), or hard storage media, such as a hard disk drive or an interchangeable optical disk storage system (e.g., compact disk drive or digital video disk drive). Memory block 130 may include a memory section for storage of instructions and data used by controller 1 16 as well as a memory section for audio and video signal storage. Controller 1 16 may also allow storage of signals in memory block 130 in an alternate form (e.g., an MPTS or SPTS from transport decoder 108 or transport decoder 1 14).

Controller 1 16 is also connected to an external communications interface 120. External communication interface 120 may provide signals for establishing billing and use of the service provider content. External communications interface 120 may include a phone modem for providing phone connection to a service provider. External communications interface 120 may also include an interface for connection to an Ethernet network and/or to home wireless communications network. The Ethernet network and/or home wireless network may be used for communication data, audio, and/or video signals and content to and from other devices connected to the Ethernet network and/or home wireless network (e.g., other media devices in a home).

Controller 1 16 also connects to a security interface 1 18 for communicating signals that manage and authorize use of the audio/video signals and for preventing unauthorized use. Security interface 1 18 may include a removable security device, such as a smart card. User control is accomplished through user panel 122, for providing a direct input of user commands to control the set top box and remote control receiver 124, for receiving commands from an external remote control device. Although not shown, controller 1 16 may also connect to the tuners 105, 1 10, link circuits 106, 1 12, and transport decoders 108, 1 14 to provide initialization and set-up information in addition to passing control information between the blocks. Finally, power supply 128 typically connects to all of the blocks in set top box 102 and supplies the power to those blocks as well as providing power to any of the elements needing power externally, such as the ODU 101 . Controller 1 16 also controls ODU control 132. ODU control 132 provides signaling and power supply electrical power back to the ODU 101 through filter 103. ODU control 132 provides these signals and power onto the co-axial cable(s) running between ODU 101 and set top box 102. In one embodiment, the ODU control 132 receives input control signals from controller 1 16 and provides different DC voltage levels to specific portions of the ODU 101 to provide a certain signal stream containing a set of programs or content to filter 103 and further to tuner 105 and tuner 1 10. In another embodiment, the ODU control 132 receives inputs from controller 1 16 and also from link circuit 106 and link circuit 1 12 and provides DC voltage levels and a separate tuning control signal to ODU 101 using low frequency carrier based frequency shift keying modulation. Controller 1 16 also may send control commands to disable ODU controller 130 from providing either direct current (DC) voltages or control signals to ODU 101 .

MoCA circuit 134 amplifies and processes the MoCA signal both for reception and transmission. As described above the MoCA interface permits communications of audio and video signals in a home network and may operate bi-directionally. MoCA circuit 134 includes a low noise amplifier for improving reception performance of a MoCA signal received by signal receiving device 100 from another network connected device. The received and amplified signal is tuned, demodulated, and decoded. The decoded signal may be provided to a number of other circuits, including audio and video outputs as well as a mass storage device (e.g., hard disk drive, optical drive, and the like), not shown. Additionally, MoCA circuit 134 generates and formats the MoCA transmit signal using audio and video content available in signal receiving device, including content received from the input (e.g., satellite signal) and content from the mass storage device. MoCA circuit 134 also includes a power amplifier for increasing the transmitted signal level of the MoCA signal sent by signal receiving device 100 to another network connected device. Adjustment of the receive signal amplification as well as the transmit signal amplification in MoCA circuit 134 may be controlled by controller 1 16. It should be appreciated by one skilled in the art that the blocks described inside set top box 102 have important interrelations, and some blocks may be combined and/or rearranged and still provide the same basic overall functionality. For example, transport decoder 108 and transport decoder 1 14 may be combined and further integrated along with some or all of the functions of controller 1 16 into a System on a Chip (SoC) that operates as the main controller for set top box 102. Further, control of various functions may be distributed or allocated based on specific design applications and requirements. As an example, link circuit 106 may provide control signals to ODU control 132 and no connection may exist between link circuit 1 12 and ODU control 132.

Further, it should be appreciated although ODU 101 includes both a dish and LNB for use with satellite signals and a terrestrial antenna, other embodiments may use separate structures. In some embodiments, the satellite dish and LNB and included in one structure and the terrestrial antenna is part of a second structure. The outputs of both satellite dish/LNB structure and terrestrial antenna are combined using a signal combining circuit and provided to set top box 102.

Although set top box 102 is described above as receiving a single converted signal stream, set top box 102 may also be configured to receive two or more separate converted signal streams supplied by ODU 101 in some modes of operation. Operation in these modes may include additional components including switches and/or further tuning and signal receiving components, not shown. Further, set top box 102 may be designed to operate only on a home network using the Ethernet or home wireless network interfaces described above. In this case, the elements associated with operation in a MoCA network may be removed from set top box 102.

As described earlier, the lowest potential ground point in a satellite box may be a ground point or shell of an F-connector located between filter 103 and ODU 101 . In order to mitigate or control the effects of current induced into set top box 102 due to an ESD or surge event, a wide strip of conductive copper material is included in printed circuit board. The strip may connect the ground for components in set-top box 102, such as components in user panel 122, remote control receiver 124, and/or audio/video output 126, to the ground at the F-connector. The ingress point or points for the current in the components are connected to ground in the strip. An ingress point may be, but is not limited to, the grounded shell shield of a connector or button, the ground connection of an ESD protection diode, an externally accessible push button switch, an LED, or any electrical connection that could conduct currents from an external ESD or surge event. The strip is separated from the main ground of the board that connects the grounds of the remaining components or structures in set top box 102. The strip is connected to the board ground at the F-connector. The separation between the strip and board ground prevents a potential difference in ground potential from occurring across the board ground due to high current as a result of the ESD or surge event and the resistance and inductance in the conductive material used for the ground. Further details regarding controlling current due to an ESD or surge event will described below. Turning to FIG. 2, a diagram of an exemplary circuit 200 including a ground structure in a device in accordance with the present disclosure is shown. Circuit 200 may be included as part of set top box 102 used as part of system 100 described in FIG. 1 . Circuit 200 may alternatively be used as part of an entertainment device, communication receiver, transmitter, and/or transceiver device including, but not limited to, a handheld radio, a gateway, a modem, a cellular or wireless telephone, a television, a home computer, a tablet, and a media content player. It is important to note that several components and interconnections necessary for complete operation of circuit 200 are not shown in the interest of conciseness, as the components not shown are well known to those skilled in the art.

In circuit 200, SoC 205 connects to memory 210 through connection 212 and memory 215 through connection 217. SoC 205 also connects to button 220 through connection 222 and button 225 through connection 227. Further, SoC 205 connects to infra-red (IR) receiver 230 through connection 232. Finally, SoC 205 connects to RF circuit 235 through connection 237. RF circuit 235 further connects to RF connector 240. SoC 205, memory 210, memory 215, and RF circuit 235 are connected into ground plane 250. Button 220, button 225, and IR receiver 230 are connected into ground trace 260. RF connector 240 is connected into both ground plane 250 and ground trace 260. Slot 265 is shown between ground plane 250 and ground trace 260. SoC 205 operates as the main controller for circuit 200. For example, SoC 205 may combine the functions of demodulating, transport decoding, and other signal processing similar to those functions described for link circuit 106, transport decoder 108, controller 1 16, and Audio/video output 126 described in FIG. 1 . Memory 210 and memory 220 operate and may be configured in a manner similar to memory 130 in FIG. 1 . Memory 210 and memory 220 may, for instance, store operational code for SoC 205, or store all or portions of a signal stream received by SoC 205 through RF circuit 235.

Button 220 and button 225 are part of a user interface provided directed to the device that includes circuit 200 (e.g., set top box 102 in FIG. 1 ). IR receiver 230 operates in a manner similar to remote control receiver 124 described in FIG. 1 . IR receiver 230 allows a user to operate the device without having to use button 220 and button 225.

RF circuit 235 may include filters, amplifiers, mixers, oscillators, and converters for processing the received signal from RF connector 240. For example, RF circuit 235 may process signals in a manner similar to filter 103 and tuner 105 described in FIG. 1 .

Elements SoC 205, memory 210, memory 215, button 220, button 225, IR receiver 230, RF circuit 235 and RF connector 240 are located on a multilayer printed circuit board. The multi-layer printed circuit board may include one or more layers used for connecting and grounding the elements together. Ground plane 250 as well as ground trace 260 may be formed on one or more of these layers.

As described earlier, a surge event may occur during operation of circuit 200. For instance, a user, while carrying a static electric charge, may contact an external element of circuit 200, such as button 220, button 225, or IR receiver 230. The ESD that occurs from the user due to the static electric charge may enter the element and conduct into the ground of the element. The ESD causes high current to flow. The current that flows into the ground of the element will continue to flow into the ground used in circuit 200. This current, if allowed to flow into ground plane 250, may disturb the operation of SoC 205, memory 210, or memory 210 including damaging those elements.

However, the ground for the element (e.g., button 220, button 225, or IR receiver 230) uses ground trace 260 instead of ground plane 250. Ground trace 260 is separated from ground plane 250 by slot 265 and provides a separate and otherwise direct ground connection between the element and F- connector 240. The high current from the ESD or surge that enter the ground at the element is conducted to the ground on F-connector 240 and further exits circuit 200 through the ground on the external cable connected to F- connector 240. Slot 265 isolates the current flow from the ground for the element. Slot 265 extends from the element to F-connector 240 and allows ground trace 260 to connect to ground plane 250 only at that point. The width of slot may be a width that prevents unexpected coupling, including inductive or capacitive coupling, between ground trace 260 and ground plane 250. In one embodiment, slot 265 is .25 millimeters wide. As a result, ground trace 260 provides a separate and electrically isolated ground path for conducting current from ESD or surge current susceptible components, such as switches, buttons, and IR receivers, to the F-connector that is separated from the main board ground used for the remaining circuits.

It is important to note that the elements, such as button 220, button 225, or IR receiver 230, are often located at almost the farthest point from F- connector 240. For example, button 220, button 225, and IR receiver 230 may be located for use on a front panel of a device while F-connector 240 may be located for use on the back panel.

Elements, such as button 220, button 225, and IR receiver 225, may include a common ground point. In such a configuration, the ground current associated with the signal connection (e.g., connection 222, connection 227, and connection 232) will also be directed through ground trace 260. In some cases signal performance may be affected by the long and positionally different ground connection between the element and ground plane 250 used by SoC 205 with respect to the signal connection. In order to address this issue, more than one ground connection may be provided for any or all of the elements. For instance, button 220, button 225, and/or IR receiver 225 may include a metal or conductive shield with a ground connection separate from the signal ground connection for the element. The ground for the shield, which is more likely to be contacted or otherwise absorb the ESD or surge current, may be connected to ground trace 260. A second ground connection for button 220, button 225, and/or IR receiver 230 may be connected to ground plane 250 through connection 222, connection 227, or connection 232 (e.g., at SoC 205).

Ground trace 260 may also include portion of the conductive surface that is exposed by removing the top surface solder resist mask. The exposed conductive surface may be located at or near an element (e.g.,) that is prone to ingress from an ESD or surge event. The expose conductive surface may induce the current from the ESD or surge event into ground trace 260 without allowing the current to enter into the element of the ground structure for the element.

It is important to note that circuit 200 includes elements, such as button 220, button 225, and IR receiver 230, incorporated directly or mounted on a printed circuit board used for circuit 200. These elements are typically associated with a front panel interface for a device (e.g., set-top box 102 described in FIG. 1 ). The arrangement in circuit 200 may be easily adapted for an arrangement that includes a separate front panel assembly that contains buttons and an IR receiver. A ground connection, made with a conductive wire, would connect a ground point on the separate front panel assembly to ground trace 260 in order to operate in the manner described above. Further, as described earlier, devices (e.g., set top box 102 described in FIG. 1 ) that may use circuit 200 often use a power supply circuit that does not connect directly to the low potential earth ground as part of the main power connection. However, in some cases, the ground arrangement including a separate ground trace 260 as described in circuit 200 may still be effective even when used in devices that include a low potential earth ground connected through a power supply circuit. In many systems, RF connector 240 is connected to the earth grounding rod at the signal receiving antenna (e.g., ODU 101 in FIG. 1 ) through the ground shield of a coaxial cable as part of the normal installation of the signal receiving antenna. The braided conductive ground element in coaxial cable is generally a lower impedance path for ESD to get to earth ground than the earth ground connection used in the powers supply that travels through the normal house power wiring.

Turning to FIG. 3, a diagram of another exemplary circuit 300 including a ground structure in a device in accordance with the present disclosure is shown. Circuit 300 may be included as part of set top box 102 used as part of system 100 described in FIG. 1 . Circuit 300 may alternatively be used as part of an entertainment device, communication receiver, transmitter, and/or transceiver device including, but not limited to, a handheld radio, a gateway, a modem, a cellular or wireless telephone, a television, a home computer, a tablet, and a media content player. It is important to note that several components and interconnections necessary for complete operation of circuit 300 are not shown in the interest of conciseness, as the components not shown are well known to those skilled in the art.

In circuit 300, SoC 305 connects to memory 310 through connection 312 and memory 315 through connection 317. SoC 305 also connects to button 320 through connection 322 and button 325 through connection 327. Further, SoC 305 connects to infra-red (IR) receiver 330 through connection 332. Additionally, SoC 305 connects to RF circuit 335 through connection 337. RF circuit 335 further connects to RF connector 340. Finally, SoC 305 connects to input/output (I/O) connector 370 through connection 372. SoC 305, memory 310, memory 315, and RF circuit 335 are connected into ground plane 350. Button 320, button 335, and IR receiver 330 are connected into ground trace 360. I/O connector 370 is connected into ground trace 375. RF connector 340 is connected into ground plane 350, ground trace 360, and ground trace 375. Slot 365 is shown between ground plane 350 and ground trace 375. Slot 380 is shown between ground plane 350 and ground trace 375. Except as described below, the operation of the elements of circuit 300 are similar to like numbered elements described for circuit 200 in FIG. 2 and will not be further described here.

I/O connector 370 may include one or more components for interfacing signals to and from circuit 300. In one embodiment, I/O connector 370 may be an HDMI connector from providing an output signal to a television in a manner similar to that described for audio/video output 126 described in FIG. 1 . In another embodiment, I/O connector 370 may by an Ethernet connector or universal serial bus (USB) connector for communicating signals on a home network, similar to external communication interface 120 described in FIG. 1 .

As with button 320, button 325, and IR receiver 330, I/O connector 370 may be prone to ingress current from an ESD or surge event. Circuit 300 includes ground trace 375 and slot 380 that operate in the same manner as described above for ground trace 260 and slot 265.

Some circuits that are used in conjunction with signals passing through an I/O connection circuits (e.g., USB, HDMI) require the ground trace 375 and ground plane 350 be connected together at I/O connector 370 in order to maintain a controlled transmission line impedance for connection 372 from I/O connector 370 to SoC 305. I/O connector 370 is connected to both ground plane 250 and ground trace 375 only at the connection 372 in order to maintain a controlled impedance (e.g., 75 ohms) for the signal traces in connection 372. Ground trace 375 still provides a separate and isolated ground path for current to F-connector 340 that is induced from an ESD or surge event. The location, position, and extension of slot 380 discourages the currents from flowing in ground plane 350 while minimally affecting connection 372.

Turning now to FIG. 4, a flow chart of an exemplary process 400 for controlling ground currents in a device caused by ESD or surge events in accordance with the present disclosure is shown. Process 400 will primarily be described with respect to circuit 200 described in FIG. 2. The steps of process 400 may equally apply to circuit 300 described in FIG. 3. Additionally, one or more of the steps in process 400 may be equally applicable to set top box 102 described in FIG. 1 . Further, it is important to note that some of the steps described in process 200 may be implemented more than once, may be implemented recursively, or may be omitted. Such modifications may be made without any effect to the overall aspects of process 400.

At step 410, operation of the device is initialized. The initialization, at step 410, may include for example, a user pressing a power button (e.g., button 220) on the device. At step 420, an ESD or surge event occurs with the device. The ESD or surge event induces current into components and/or the circuit board ground of circuit 200. The event may be caused, for instance, by the user pressing the button press to initialize the device, in step 410, after the body of the user has become electrostatically charged. The ESD may induce current into a shield around the power button (e.g., button 220).

At step 430, after the current is induced into circuit 200 at step 420, circuit 200 provides a ground path through an isolated or separated ground trace to an RF-connector. In one embodiment, the induced current is conducted through ground trace 260 to F-connector 240 where it egresses from the device through the ground shield on a cable connected to F- connector 240. Slot 265 isolates the current flowing, at step 430, in the ground for the element. Slot 265 extends from the element to F-connector 240 and allows ground trace 260 to connect to ground plane 250, used for other elements in circuit 200 sensitive to current from an ESD or surge event, only at that point. Slot 265 also effectively lowers the resistance or impedance for the current to pass to F-connector 240 through ground trace 260 with respect to passing through ground plane 250. As a result, ground trace 260 provides a separate ground path for ESD or surge current susceptible components, such as switches, buttons, and IR receivers, to the F-connector and that is separated from the main board ground used for the remaining circuits.

The embodiments described above relate to an apparatus and method for controlling current due to ESD or other surge events in a device. In particular, the embodiments describe a grounding mechanism for controlling this current within a ground plane in a printed circuit board in the device. The mechanism provides a separate electrically conductive path for current due to ESD and surge events, often referred to as unwanted current or charge induced current, from external sources. The path allows the unwanted current to conduct to the lowest potential ground connection available for the printed circuit board as well as the device. The separate path may also be lower in resistance or impedance to the unwanted current than the other remaining ground structure. The mechanism greatly diminishes the possibility of the unwanted current disrupting normal electronic circuit operations, such as resetting or locking-up the device. Although embodiments which incorporate the teachings of the present disclosure have been shown and described in detail herein, those skilled in the art can readily devise many other varied embodiments that still incorporate these teachings. Having described preferred embodiments of an apparatus and method for controlling current in a device due to an ESD or surge event (which are intended to be illustrative and not limiting), it is noted that modifications and variations can be made by persons skilled in the art in light of the above teachings. It is therefore to be understood that changes may be made in the embodiments of the present disclosure which are within the scope of the disclosure as outlined by the appended claims.

Claims

WHAT IS CLAIMED IS:

1 . An apparatus (300) comprising:

a first interface (320, 325, 330, 370), the first interface providing a first signal to a main control circuit (305), the signal being at least one of a data signal and a control signal;

a radio frequency connector (340), the radio frequency connector providing a second signal received from a broadcast signal source to the main control circuit (305); and

a ground connection (360) on a printed circuit board, the ground connection (360) conductively connecting a ground point at the first interface (320, 325, 330, 370) to a ground point at the radio frequency connector (340), the ground connection (360) used for controlling unwanted current induced at the first interface (320, 325, 330, 370) such that the unwanted current does not affect an operation of the main control circuit (305).

2. The apparatus (300) of claim 1 , wherein the first interface (320, 325, 330, 370) is located at the front of the apparatus (300) and the radio frequency connector (340) is located at the back of the apparatus.

3. The apparatus (300) of claim 1 , wherein the unwanted current is induced by an electrostatic discharge caused by a user being in proximity to the apparatus (300).

4. The apparatus (300) of claim 1 , wherein the first interface (320, 325, 330, 370) further includes a ground connection associated signal that is provided to the main control circuit (305), the ground connection associated with the signal being separate from the ground connection (360) connecting the ground point at the first interface (320, 325, 330, 370) to the ground point at the radio frequency connector (340).

5. The apparatus (300) of claim 4, wherein the first interface (320, 325, 330, 370) includes a conductive shield that connects only to the ground connection (360) connecting the ground point at the first interface (320, 325, 330, 370) to the ground point at the radio frequency connector (340).

6. The apparatus (300) of claim 4, wherein the ground connection for the signal is part of a controlled impedance transmission line structure on a multilayer printed circuit board.

7. The apparatus (300) of claim 1 , wherein the ground connection (360) connecting the ground point at the first interface (320, 325, 330, 370) to the ground point at the radio frequency connector (340) is part of a conductive ground layer on a multi-layer printed circuit board.

8. The apparatus (300) of claim 7, wherein a ground point for the main control circuit (305) is part of the ground layer on the multi-layer printed circuit board and the ground point for the main control circuit (305) and the ground connection connecting the ground point at the first interface (320, 325, 330, 370) to the ground point at the radio frequency connector (340) are separated by a slot in the conductive ground layer.

9. The apparatus (300) of claim 7, wherein the ground connection (360) connecting the ground point at the first interface (320, 325, 330, 370) to the ground point at the radio frequency connector (340) is located on a top surface of the multi-layer printed circuit and include a conductive region that is not covered by a solder resist mask and is located near the first interface (320, 325, 330, 370).

10. The apparatus (300) of claim 1 , wherein the radio frequency connector (340) is an F-connector.

1 1 . The apparatus (300) of claim 1 , wherein the first interface (320, 325, 330, 370) is a digital audio/video connector.

12. The apparatus (300) of claim 1 , wherein the first interface (320, 325, 330, 370) is a front panel interface for use in controlling the apparatus by a user.

13. The apparatus (300) of claim 12, wherein the front panel interface includes at least one of a button, a light source, and infra-red receiver.

14. The apparatus (300) of claim 1 , wherein the unwanted current causes at least one of a lock up of a controller, a reset of the controller, and a state change in a memory circuit connector to the controller, in the main control circuit (305).

15. The apparatus (300) of claim 1 , wherein the apparatus (300) is a signal receiving device for receiving signals provided by a satellite signal service provider.

16. A method (400), comprising:

inducing (420) an unwanted current into a printed circuit board of a device; and

providing (430) a conductive path for the unwanted current on the printed circuit board from a ground at an ingress point for the unwanted current to a ground point at a radio frequency connector such that the unwanted current does not affect an operation of a circuit connected on the printed circuit board.

17. The method (400) of claim 16, wherein the unwanted current is induced by an electrostatic discharge caused by a user being in proximity to the device.

18. The method (400) of claim 16, wherein the unwanted current is induced through a front panel interface for use in controlling the device by a user.

19. The method (400) of claim 18, wherein the front panel interface includes a conductive shield that connects only to the conductive path for the unwanted current.

20. The method (400) of claim 18, wherein the printed circuit board is a multilayer circuit board and wherein conductive path for the unwanted current is located on a top surface of the multi-layer printed circuit and includes a conductive region located near the front panel interface that is not covered by a solder resist mask.

21 . The method (400) of claim 18, wherein the front panel interface includes at least one of a button, a light source, and infra-red receiver.

22. The method (400) of claim 21 , wherein the conductive path for the unwanted current on the printed circuit board from the ground at an ingress point to the ground point at a radio frequency connector is separate from a conductive path for a ground connection associated with a signal that is provided between the at least one of a button, a light source, and infra-red receiver and the circuit connected on the printed circuit board.

23. The method (400) of claim 22, wherein the printed circuit board is a multilayer printed circuit board and wherein the conductive path for the ground connection associated with the signal that is provided between the at least one of a button, a light source, and infra-red receiver and the circuit is part of a controlled impedance transmission line structure on the multi-layer printed circuit board

24. The method (400) of claim 16, wherein the radio frequency connector is an F-connector.

25. The method (400) of claim 16, wherein the unwanted current causes at least one of a lock up of a controller, a reset of the controller, and a state change in a memory circuit connector to the controller in the device.

26. The method (400) of claim 16, wherein the ingress point for the unwanted current is located at the front of the device and the radio frequency connector is located at the back of the device.

27. The method (400) of claim 16, wherein the device is a signal receiving device for receiving signals provided by a satellite signal service provider.

28. The method (400) of claim 16, wherein the unwanted current is induced in a digital audio/video connector.

29. The method (400) of claim 16, wherein the printed circuit board is a multilayer printed circuit board and wherein the conductive path for the unwanted current is part of a conductive ground layer on the multi-layer printed circuit board.

30. The method (400) of claim 29, wherein a conductive path for the ground current for the circuit connected on the printed circuit is also part of the ground layer on the multi-layer printed circuit board and wherein the conductive path for the ground current for the circuit connected on the printed circuit and the conductive path for the unwanted current are separated by a slot in the conductive ground layer.