Communication device

Abstract

Disclosed is a communication device in which interference between filter components on a printed circuit board is suppressed while high-frequency characteristics are preserved. The communication device includes a printed circuit board 30 having: a plurality of differential signal line pairs 200, 201 formed in a distributed manner on respective sides of the circuit board, the differential signal lines pairs connecting a communication LSI 110 to a connector 120; and common mode choke coils 130, 131 provided midway between lines of the respective differential signal line pairs 200, 201. The common mode choke coils 130 and 131 are arranged on respective surfaces of the printed circuit board 30 so as to overlap each other in the thickness direction of the printed circuit board. An internal wiring layer of the printed circuit board 30 has a frame ground wiring 300 and a signal ground wiring 400 formed therein such that the frame ground wiring 300 and / or the signal ground wiring 400 is positioned between the common mode choke coils 130 and 131.

Description

Communication device

[0001] The present invention relates to a communication device that transmits signals over a network, and more particularly to a communication device that includes a plurality of connectors to which cables for transmitting signals are connected.

[0002] In recent years, the development of autonomous driving systems and the advancement of driver assistance systems have been rapidly progressing from the perspective of reducing traffic accidents and alleviating the burden of driving operations on drivers. In recent years, functions such as hands-free, which controls the steering of the vehicle without driver input under specific conditions, and eyes-free, which allows the driver to take their eyes off the road, have been realized. Automated driving electronic control units (AD-ECUs) and advanced driver assistance system electronic control units (ADAS-ECUs) that realize these functions have numerous sensors, such as cameras, LiDAR (Light Detection and Ranging), and sonar, connected by cables to acquire information from the outside world.

[0003] Furthermore, as new features such as connectivity, personalization, and infotainment are added, the electrical / electronic architecture (E / E architecture) of automobiles is evolving into a vehicle-centralized "zone architecture" that integrates processing for powertrain, body system, and safety system domains into the vehicle's central computer. As a result, the integrated ECU, which acts as the vehicle's central computer, will be connected to numerous cables for backbone transmission with the zone ECUs located in each zone within the vehicle.

[0004] As the in-vehicle systems become more advanced and multifunctional, the amount of data transmitted between ECUs has been increasing, and the standardization of in-vehicle network specifications enabling transmission speeds of Gbps or higher has been progressing. Also, in communication with sensors centered around cameras, the standardization of a method of differential transmission of high-speed signals exceeding Gbps using a twisted pair cable has been advancing. Furthermore, in these specifications, for harness weight reduction, the standardization of a power-over-data-line (PoDL) power superimposition technique for superimposing power on the cable for data transmission has also been progressing.

[0005] Such high-speed networking is progressing not only in in-vehicle control devices but also in communication devices in various fields. In a high-speed network, the current spectrum used for data transmission exists at a high level up to the region exceeding GHz, and it is necessary to suppress the radiation of electromagnetic waves in the high-frequency band. Also, since elements such as communication LSIs process signals up to the GHz band, it is necessary to suppress the intrusion of noise in the GHz band.

[0006] In such high-speed data transmission, for example, Patent Document 1 discloses a printed circuit board configured to cancel in-phase noise transmitted through a differential signal line pair using a common-mode filter.

[0007] Japanese Unexamined Patent Application Publication No. 2015-231006

[0008] Among communication devices, some, like in-vehicle control devices such as the above-described AD / ADAS-ECU and integrated ECU, are required to be miniaturized due to installation space constraints. When the number of cables connected to a communication device increases, the number of common-mode filters provided on the printed circuit board also increases. Therefore, when trying to connect more cables using a plurality of connectors, in order to avoid interference in the placement locations of the filter components constituting the common-mode filter, it is necessary to increase the distance between the connectors, which poses a problem that it becomes difficult to miniaturize the housing.

[0009] In view of the above-mentioned problems, the object of the present invention is to reduce the size of the printed circuit board and, consequently, the communication device, by narrowing the spacing between connectors while avoiding interference between filter components on the printed circuit board.

[0010] A communication device according to the present invention, in one preferred embodiment, includes a printed circuit board having an internal wiring layer on which a first ground wire and a second ground wire are formed; a connector portion disposed on the printed circuit board to which a plurality of pairs of cables, each transmitting differential signals, are connected; a communication element disposed on the printed circuit board to process the differential signals transmitted by the plurality of pairs of cables; a first signal line pair formed on one side of the printed circuit board to connect the connector portion and the communication element and to transmit a first differential signal among the differential signals transmitted by the plurality of pairs of cables between the connector portion and the communication element; and a connector formed on the other side of the printed circuit board to connect the connector portion and the communication element and to transmit the differential signals transmitted by the plurality of pairs of cables. The device comprises: a second signal line pair for transmitting a second differential signal, which is different from a first differential signal among the transmitted differential signals, between the connector and the communication element; a first filter provided in the middle of the first signal line pair and positioned on one side of the printed circuit board to reduce common-mode noise; and a second filter provided in the middle of the second signal line pair and positioned on the other side of the printed circuit board, positioned so that at least a portion of it overlaps with the first filter in the thickness direction of the printed circuit board to reduce common-mode noise, wherein at least one of the first and second ground lines extends into the region where the first and second filters overlap in the thickness direction of the printed circuit board and is formed to cover at least a portion of the overlapping region.

[0011] A communication device according to the present invention, in another preferred embodiment, comprises: a printed circuit board having a plurality of internal wiring layers on which at least one of a first ground wiring and a second ground wiring is formed; a connector portion disposed on the printed circuit board to which a plurality of pairs of cables, each transmitting differential signals, are connected; a communication element disposed on the printed circuit board to process the differential signals transmitted by the plurality of pairs of cables; a first signal line pair formed on one side of the printed circuit board to connect the connector portion and the communication element and to transmit a first differential signal among the differential signals transmitted by the plurality of pairs of cables between the connector portion and the communication element; and a first signal line pair formed on the other side of the printed circuit board to connect the connector portion and the communication element and to transmit a first differential signal among the differential signals transmitted by the plurality of pairs of cables. The device comprises: a second signal line pair that transmits a second differential signal different from a first differential signal between the connector and the communication element; a first filter provided in the middle of the first signal line pair and positioned on one side of the printed circuit board to reduce common-mode noise; and a second filter provided in the middle of the second signal line pair and positioned on the other side of the printed circuit board, positioned such that at least a portion of it overlaps with the first filter in the thickness direction of the printed circuit board to reduce common-mode noise, wherein at least one of the plurality of internal wiring layers has at least one of a first ground wire and a second ground wire that extends into the region where the first filter and the second filter overlap in the thickness direction of the printed circuit board and is formed to cover at least a portion of the overlapping region.

[0012] According to the present invention, interference between filter components on a printed circuit board can be avoided, connectors can be installed at a high density by narrowing the spacing between them, and the printed circuit board can be miniaturized, thereby enabling the miniaturization of communication devices. Other novel features of the present invention and the technical problems solved thereby will become clear from the description and drawings herein.

[0013] This is a schematic exploded perspective view showing the configuration of one embodiment of an in-vehicle control device, which is an example of a communication device to which the present invention is applied. This is a schematic external view of a part of the connection portion between the communication LSI and the connector of the printed circuit board, viewed from the front. This is a schematic external view of a part of the connection portion between the communication LSI and the connector of the printed circuit board, viewed from the back. This is a schematic diagram showing an example of ground wiring formed in the internal wiring layer of the printed circuit board in the region between the communication LSI and the connector. This is a schematic cross-sectional view of the dashed-dotted line A-A in Figure 4, viewed in the direction of the arrow. This is a schematic plan view showing an example of ground wiring formed in the internal wiring layer of the printed circuit board in the second embodiment. This is a schematic cross-sectional view of the dashed-dotted line B-B in Figure 6, viewed in the direction of the arrow. This is a schematic plan view showing an example of ground wiring formed in the internal wiring layer of the printed circuit board in the third embodiment. This is a schematic cross-sectional view of the dashed-dotted line C-C in Figure 8, viewed in the direction of the arrow. This is a schematic plan view showing an example of ground wiring formed in the internal wiring layer of the printed circuit board in the fourth embodiment. This is a schematic cross-sectional view of the dashed-dotted line D-D in Figure 10, viewed in the direction of the arrow.

[0014] Hereinafter, representative embodiments of the present invention will be described with reference to the drawings. Note that the embodiments and drawings described below are illustrative examples for explaining the present invention, and have been omitted or simplified as appropriate for clarity of explanation. Furthermore, please note that the position, size, shape, and extent of each component shown in the drawings may not necessarily accurately represent them, in order to facilitate understanding of the invention.

[0015] Figure 1 is a schematic exploded perspective view showing the configuration of one embodiment of an in-vehicle control device, which is an example of a communication device to which the present invention is applied.

[0016] The in-vehicle control device 10 may be, for example, an AD / ADAS-ECU that performs autonomous driving or assists the driver's driving operations while communicating with various control units that control multiple sensing devices and equipment such as the engine, brakes, and steering, or it may be an integrated ECU that aggregates and integrates information from zone ECUs located in various parts of the vehicle to perform integrated control. Here, control devices such as these devices that are mounted on a vehicle and perform processing to realize various functions by connecting multiple devices and equipment via a network are collectively referred to as in-vehicle control devices.

[0017] The in-vehicle control device 10 of this embodiment is configured by housing a printed circuit board 30, on which electronic circuits are formed, in a space within a housing composed of, for example, a metal base housing 20 and a cover 25. The housing does not necessarily have to be made of metal and may be made of, for example, a resin material, but it is desirable that electromagnetic shielding be provided at least in the parts where high-speed signals are handled.

[0018] The printed circuit board 30 is equipped with a microcontroller unit (MCU) 100 that constitutes the in-vehicle control system, multiple communication LSIs 110, and multiple connectors 120 to which cables for network connection are connected.

[0019] The MCU100 is equipped with an arithmetic unit, memory, and I / O ports, and by executing processing according to the program stored in memory using the arithmetic unit, it can realize the functions implemented as an in-vehicle control device.

[0020] The printed circuit board 30 has a connector section on its outer edge, to which a plurality of connectors 120 are provided, to which cables for transmitting data signals are connected. For data transmission, for example, a shielded twisted-pair cable (STP cable) that is metal-coated and transmits data signals as differential signals is used. In addition to a type that connects a pair of signal lines, a multi-pole type connector that can connect multiple pairs of signal lines can be used for the connector 120.

[0021] The communication LSI 110 is located between the MCU 100 and the connector 120. It converts data received from the MCU 100 into data signals that can be transmitted via the cable connected to the connector 120 and transmits them, and also converts data signals sent via the cable into data that the MCU 100 can handle and sends them to the MCU 100.

[0022] Figure 2 is a schematic view of a portion of the connection between the communication LSI 110 and the connector 120 of the printed circuit board 30, as seen from the front side. For the sake of explanation, in this specification, the side of the printed circuit board 30 on which the communication LSI 110 is mounted is referred to as the front surface, and the opposite side is referred to as the back surface.

[0023] In Figure 2, two communication LSIs 110a and 110b are arranged on the surface of the printed circuit board 30. Connectors 120a and 120b are arranged on the outer edge of the printed circuit board 30. In this specification, when distinguishing between similar components and wiring having the same function, an alphabetical subscript will be added after the reference number. When there is no need to particularly distinguish between them and they are described in general terms, the alphabetical subscript will be omitted.

[0024] The communication LSI 110 is capable of inputting and outputting four sets of differential signals and has four sets of eight input / output terminals that can connect four sets of signal line pairs. Of the four sets of input / output terminals of the communication LSI 110, two sets are connected to signal line pairs 200 formed on the surface of the printed circuit board 30. The other two sets of input / output terminals are led to the back surface of the printed circuit board 30 via vias 210 and connected to signal line pairs formed on the back surface, as will be described later.

[0025] The connector 120 is a multi-pin connector capable of connecting four pairs of cables, and has four sets of eight connection terminals to which four pairs of signal lines 200 can be connected. Similar to the communication LSI 110, two of the four sets of connection terminals of the connector 120 are connected to signal line pairs 200 formed on the surface of the printed circuit board 30, and the other two sets are connected via vias 220 to signal line pairs formed on the back of the printed circuit board 30.

[0026] The signal line pairs 200 are formed on the surface of the printed circuit board 30 and connect the communication LSI 110 and the connector 120 on the surface of the printed circuit board 30. Specifically, signal line pairs 200a and 200b connect the communication LSI 110a and the connector 120a, and signal line pairs 200c and 200d connect the communication LSI 110b and the connector 120b. Note that the communication LSI 110 and the connector 120 do not need to correspond one-to-one in this way; one communication LSI 110 may be connected to multiple connectors 120, and conversely, one connector 120 may be connected to multiple communication LSIs 110.

[0027] Common mode choke coils 130a, 130b, 130c, and 130d are connected to the signal line pairs 200a, 200b, 200c, and 200d, respectively. The common mode choke coil 130 functions as a filter (common mode noise filter) that suppresses the transmission of in-phase noise components superimposed on the differential signals transmitted by the signal line pairs 200 from the connector 120 to the communication LSI 110, or from the communication LSI 110 to the connector 120.

[0028] A coupling capacitor 140 is connected to each signal line that makes up the signal line pair 200, which connects the common mode choke coil 130 and the connector 120, to block the DC component.

[0029] Furthermore, between each signal line constituting the signal line pair 200 and the ground wire, a termination component consisting of a resistor 150 and a capacitor 160 connected in series, and an ESD element 170 that protects the circuit from surge voltages such as static electricity are connected. The ground wire side terminal of the capacitor 160 constituting the termination component is connected to the frame ground wire formed on the surface of the printed circuit board 30, and / or to the frame ground wire formed in the internal wiring layer of the printed circuit board 30 via a via 230. Similarly, the ground side terminal of the ESD element 170 is connected to the frame ground wire formed on the surface of the printed circuit board 30, and / or to the frame ground wire formed in the internal wiring layer of the printed circuit board 30 via a via 240.

[0030] The coupling capacitor 140, termination components (resistor 150 and capacitor 160), and ESD element 170 do not necessarily have to be located on the connector 120 side; some or all of them may be located on the communication LSI 110 side of the common mode choke coil 130. In this case, the terminals on the ground side of the termination components and ESD element are connected to the signal ground wiring, which becomes the reference potential of the electronic circuit including the communication LSI 110 on the printed circuit board 30.

[0031] Please note that in Figure 2, for the sake of clarity, frame ground wiring and signal ground wiring formed on the printed circuit board 30, circuit components other than those mentioned above, the signal wiring connecting them, and power supply wiring are omitted from the illustration.

[0032] Figure 3 is a schematic view of a portion of the connection area between the communication LSI 110 and the connector 120 of the printed circuit board 30, as seen from the back.

[0033] Figure 3 shows the back surface of the printed circuit board 30 corresponding to the portion shown in Figure 2, and the communication LSIs 110a and 110b and connectors 120a and 120b located on the front surface of the printed circuit board 30 are shown by dashed lines.

[0034] The via 210 to which the input / output terminals of the communication LSIs 110a and 110b are connected, and the via 220 connected to the connector terminal are connected by signal line pairs 201a, 201b, 201c, and 201d.

[0035] Common mode choke coils 131a, 131b, 131c, and 131d are connected to the signal line pairs 201a, 201b, 201c, and 201d, respectively. The common mode choke coils 131a, 131b, 131c, and 131d are arranged so as to overlap with the common mode choke coils 130a, 130b, 130c, and 130d in the thickness direction of the printed circuit board 30 (so that they overlap when the board surface of the printed circuit board 30 is viewed from the front or back side).

[0036] A coupling capacitor 141 is connected to each signal line that makes up the signal line pair 201, which connects the common mode choke coil 131 and the connector 120, to block the DC component.

[0037] Furthermore, similar to the signal line pair 200, a termination component consisting of a resistor 151 and a capacitor 161 connected in series, and an ESD element 171 that protects the circuit from surge voltages such as static electricity are connected between each signal line constituting the signal line pair 201 and the ground wire. These ground wire terminals are connected to frame ground wiring formed on the back surface and / or to frame ground wiring formed in the internal wiring layer of the printed circuit board 30 via vias 230 and 240.

[0038] The coupling capacitor 141, the resistor 151, the capacitor 161, and the ESD element 171 that constitute the termination components are arranged in a manner similar to the common mode choke coil, so as to substantially overlap with the coupling capacitor 140, the resistor 150, the capacitor 160, and the ESD element 170 that are placed on the surface, in the thickness direction of the printed circuit board 30. This allows vias 230 and 240 to be easily shared between components placed on the surface and components placed on the back of the printed circuit board 30. Note that, similar to the corresponding components on the surface, some or all of the coupling capacitor 141, termination components (resistor 151 and capacitor 161), and ESD element 171 may be located on the communication LSI 110 side of the common mode choke coil 130.

[0039] It should be noted that the components placed on the front and back surfaces of the printed circuit board 30 do not necessarily need to overlap each other in the thickness direction of the printed circuit board 30. However, it is desirable that the common mode choke coils 130 and 131, which occupy a relatively large area on the printed circuit board 30, be arranged so that at least a portion of them overlap each other.

[0040] Figure 4 is a schematic diagram showing an example of a ground wiring pattern formed in the internal wiring layer of the printed circuit board 30 in the region between the communication LSI 110 and the connector 120. Note that in Figure 4, components placed on the surface of the printed circuit board 30 are also shown to facilitate understanding of their positional relationship with the components placed on the surface of the printed circuit board 30.

[0041] The frame ground wiring 300 is formed on the outer edge of the printed circuit board 30. In particular, near where the common mode choke coils 130 and 131 are located, the frame ground wiring 300 is formed extending from the connector 120 side end of the common mode choke coil 130 toward the connector 120. The shielding of the STP cable is electrically connected to the frame ground wiring 300 via the connector 120. The frame ground wiring 300 is also electrically connected to a metal screw that is screwed into the base housing, for example, at the screw fastening portion that fixes the printed circuit board 30 to the base housing, via a termination component in which a resistor and a capacitor are connected in series.

[0042] The signal ground wiring 400 is formed on the printed circuit board 30 in the area where the electronic circuit, including the MCU 100 and the communication LSI 110, is mounted. In particular, near where the common mode choke coils 130 and 131 are located, the signal ground wiring 400 is formed extending from the end of the common mode choke coil 130 on the communication LSI 110 side toward the direction toward where the communication LSI 110 is mounted. The signal ground wiring 400 provides a reference potential to the MCU 100, the communication LSI 110, and other components constituting the electronic circuit.

[0043] In the vicinity of the area where the common mode choke coil 130 is located, the frame ground wiring 300 protrudes toward the signal ground wiring 400 and is formed to cover approximately half of the area between the common mode choke coil 130 and the common mode choke coil 131.

[0044] Similarly, the signal ground wiring 400 protrudes toward the frame ground wiring 300 side and is formed to cover substantially the remaining half region between the common mode choke coil 130 and the common mode choke coil 131. A gap is provided between the frame ground wiring 300 and the signal ground wiring 400, and a region where neither the frame ground wiring 300 nor the signal ground wiring 400 exists is formed within the region between the common mode choke coil 130 and the common mode choke coil 131.

[0045] FIG. 5 is a schematic cross-sectional view of the portion of the dashed-dotted line A - A in FIG. 4 as viewed in the arrow direction. In FIG. 5, components other than the communication LSI 110a, the connector 120a, and the common mode choke coils 130b and 131b are not shown for simplification of the explanation. Further, FIG. 5 shows the state of the internal wiring layer between the common mode choke coil 130b and the common mode choke coil 131b, but the following explanation is common to the internal wiring layer between the other common mode choke coils 130. For this reason, hereinafter, the subscripts attached to the reference numerals indicating each part are omitted in the explanation.

[0046] As described above, the common mode choke coil 130 connected in the middle of the signal line pair 200 formed on the surface of the printed circuit board 30 and the common mode choke coil 131 connected in the middle of the signal line pair 201 formed on the back surface of the printed circuit board 30 are arranged such that at least a part of them overlaps in the thickness direction of the printed circuit board 30.

[0047] The printed circuit board 30 has a plurality of internal wiring layers in which frame ground wirings 300, 310 and signal ground wirings 400, 410 are formed inside. Here, only the internal wiring layers in which the ground wirings are formed are shown, but the printed circuit board 30 may have other internal wiring layers in which signal wirings are formed.

[0048] Among the plurality of internal wiring layers in which the ground wiring is formed, the frame ground wiring 300 and the signal ground wiring 400 formed in the internal wiring layer located in the middle part in the thickness direction of the printed circuit board 30 extend so as to protrude toward the region between the common mode choke coil 130 and the common mode choke coil 131 as shown in FIG. 4. The frame ground wiring 300 and the signal ground wiring 400 are formed with a gap therebetween so as to be physically separated and not contact each other.

[0049] The frame ground wiring 310 formed in other internal wiring layers is formed on the connector 120 side from the ends of the common mode choke coils 130 and 131 on the connector 120 side, and does not extend in the region direction between the common mode choke coil 130 and the common mode choke coil 131. Similarly, the signal ground wiring 410 formed in other internal wiring layers is formed on the communication LSI 110 side from the ends of the common mode choke coils 130 and 131 on the communication LSI 110 side, and does not extend in the region direction between the common mode choke coil 130 and the common mode choke coil 131.

[0050] The common mode choke coils 130 and 131 are usually arranged between the frame ground wiring and the signal ground wiring. When the common mode choke coil 130 arranged on the front surface of the printed circuit board 30 and the common mode choke coil 131 arranged on the back surface of the printed circuit board 30 are arranged at positions overlapping in the thickness direction of the printed circuit board 30 as in the present embodiment, the distance between the common mode chokes becomes close, so there is a risk of crosstalk noise due to electromagnetic interference between the two. In the present embodiment, by interposing the frame ground wiring 300 and the signal ground wiring 400 in the region where the common mode choke coils 130 and 131 arranged on the front and back surfaces of the printed circuit board 30 overlap in the thickness direction of the printed circuit board 30, the generation of crosstalk noise is suppressed.

[0051] It is desirable that the gap between the frame ground wiring 300 and the signal ground wiring 400 be small. For example, in order to reduce the generation of crosstalk noise by more than half, it is desirable that more than half of the area where the common mode choke coils 130 and 131 overlap is covered by the frame ground wiring 300 or the signal ground wiring 400.

[0052] The internal wiring layer on which the frame ground wiring 300 and signal ground wiring 400 are formed is located near an intermediate position in the thickness direction of the printed circuit board, at a distance from both the front and back surfaces. By forming the frame ground wiring 300 or signal ground wiring 400 at an intermediate position in the thickness direction of the printed circuit board 30 in this way, an increase in parasitic capacitance between the common mode choke coils 130, 131 and the frame ground wiring 300 or signal ground wiring 400 can be suppressed.

[0053] In this embodiment, as described above, signal transmission between the connector 120 and the communication LSI 110 is distributed across a signal line pair 200 provided on the front surface and a signal line pair 201 provided on the back surface of the printed circuit board 30. Accordingly, common mode choke coils 130, 131 and other components connected in the middle of the signal line pairs 200, 201 are also distributed and arranged on the front and back surfaces of the printed circuit board 30. These components are arranged so as to substantially overlap each other in the thickness direction of the printed circuit board 30. Furthermore, since frame ground wiring 300 and signal ground wiring 400 are formed in the internal wiring layer between the common mode choke coil 130 on the front surface and the common mode choke coil 131 on the back surface of the printed circuit board, electromagnetic interference that may occur between them is also suppressed.

[0054] In this way, by distributing the connection between the communication LSI 110 and the connector 120 on both the front and back surfaces of the printed circuit board 30, components such as the common mode choke coils 130 and 131 can be arranged without interfering with each other, while reducing the mounting area of ​​the required components on one side. This makes it possible to mount the connectors 120 at a high density with narrower spacing between them. As a result, the printed circuit board 30, and consequently the in-vehicle control device 10, can be miniaturized.

[0055] In this embodiment, both the frame ground wiring 300 and the signal ground wiring 400 extend into the region where the common mode choke coils 130 and 131 overlap. However, the ground wiring extending toward the overlapping region may be at least one of the frame ground wiring 300 and the signal ground wiring 400. It is not necessary for both the frame ground wiring and the signal ground wiring to be formed in each internal wiring layer; only one of them may be formed. Furthermore, the internal wiring layers on which ground wiring is formed may be limited to those on which the frame ground wiring 300 and the signal ground wiring 400 are formed.

[0056] Figure 6 is a schematic plan view showing the ground wiring pattern formed on the internal wiring layer of the printed circuit board 30 in the region between the communication LSI 110 and the connector 120 in the second embodiment, and Figure 7 is a schematic cross-sectional view of the section B-B of Figure 6 as seen in the direction of the arrow.

[0057] In Figure 6, as with Figure 4, components placed on the surface of the printed circuit board 30 are also shown to facilitate understanding of their positional relationship with the components on the surface of the printed circuit board 30. Also, in Figure 7, as with Figure 5, components other than the communication LSI 110, connector 120, and common mode choke coils 130 and 131 are omitted from the illustration for the sake of simplicity in the explanation. Note that the wiring and component placement on the front and back surfaces of the printed circuit board in this embodiment are the same as in the first embodiment, so Figures 1 to 3 and the explanations based on these drawings can be applied mutatis mutandis, and their explanations are omitted here. Furthermore, in the following, the explanation of parts common to the first embodiment will be omitted, and the explanation will focus on the differences.

[0058] In the first embodiment, since the frame ground wiring 300 and signal ground wiring 400, which are formed on the same internal wiring layer, are used as ground wiring interposed between the common mode choke coils 130 and 131, a gap is provided between the two ground wirings, as can be seen from Figures 4 and 5. In this embodiment, the frame ground wiring 300 and signal ground wiring 400, which are formed on different internal wiring layers, are used, and the area between the common mode choke coils 130 and 131 is formed to be substantially covered by either the frame ground wiring 300 or the signal ground wiring 400, as shown in Figure 6.

[0059] As shown in Figure 7, the printed circuit board 30 of this embodiment has four internal wiring layers on which ground wiring layers are formed. The frame ground wiring 300 formed on the third internal wiring layer from the surface side extends so as to protrude toward the region between the common mode choke coil 130 and the common mode choke coil 131. On the other hand, the signal ground wiring 400 is formed on the second internal wiring layer from the surface side, extending so as to protrude toward the region between the common mode choke coil 130 and the common mode choke coil 131.

[0060] In this way, by using two internal wiring layers that are closer to the middle of the printed circuit board 30 than to the surface or back surface in the thickness direction, as the frame ground wiring 300 and signal ground wiring 400 interposed between the common mode choke coils 130 and 131, the influence of parasitic capacitance between the common mode choke coils 130 and 131 and the frame ground wiring 300 and signal ground wiring 400 can be reduced.

[0061] The frame ground wiring 300 and the signal ground wiring 400 are each formed to extend to the same position along the board surface of the printed circuit board 30, up to the point where the other ground wiring extends. By extending the frame ground wiring 300 and the signal ground wiring 400 to the same position along the board surface of the printed circuit board 30 in this way, the area between the common mode choke coil 130 and the common mode choke coil 131 can be covered with almost no gaps by the frame ground wiring 300 and the signal ground wiring 400.

[0062] In this configuration, the frame ground wiring 300 and the signal ground wiring 400 are formed so that they do not overlap with each other in the thickness direction of the printed circuit board 30. This suppresses the inflow of external noise from the frame ground wiring 300 to the signal ground wiring 400 due to capacitive coupling between the two.

[0063] Note that, while the frame ground wiring 300 and signal ground wiring 400 are present, the frame ground wiring 310 and signal ground wiring 410 extend to the vicinity of the ends of the common mode choke coils 130 and 131, but do not extend into the region between the common mode choke coils 130 and 131.

[0064] In this embodiment, as in the first embodiment, components such as the common mode choke coils 130 and 131 can be arranged without interfering with each other, while reducing the mounting area of ​​the required components on one side, and enabling high-density mounting of the connectors 120 with narrower spacing between them. As a result, the printed circuit board 30 and, consequently, the in-vehicle control device 10 can be miniaturized.

[0065] Furthermore, since the area between the two common-mode choke coils 130 and 131 is covered almost completely by the frame ground wiring 300 and the signal ground wiring 400, crosstalk noise between the common-mode choke coils 130 and 131 can be suppressed more effectively than in the first embodiment.

[0066] Figure 8 is a schematic plan view showing the ground wiring pattern formed on the internal wiring layer of the printed circuit board 30 in the region between the communication LSI 110 and the connector 120 in the third embodiment, and Figure 9 is a schematic cross-sectional view of the section C-C of Figure 8 as seen in the direction of the arrow.

[0067] In Figure 8, as with Figure 4, components placed on the surface of the printed circuit board 30 are also shown to facilitate understanding of their positional relationship with the components on the surface of the printed circuit board 30. Also, in Figure 9, as with Figure 5, components other than the communication LSI 110, connector 120, and common mode choke coils 130 and 131 are omitted from the illustration for the sake of simplicity in the explanation. In this embodiment as well, the wiring and component placement on the front and back surfaces of the printed circuit board are the same as in the first embodiment, so Figures 1 to 3 and the explanations based on these drawings can be applied mutatis mutandis, and their explanations are omitted here. Furthermore, in the following, the explanation of parts common to the first embodiment will be omitted, and the explanation will focus on the differences.

[0068] In the first and second embodiments, the region between the common mode choke coils 130 and 131 is covered by the frame ground wiring 300 and the signal ground wiring 400. In contrast, in this embodiment, the region between the common mode choke coils 130 and 131 is almost entirely covered by the frame ground wiring 300 formed in the internal wiring layer, as shown in Figure 8.

[0069] The printed circuit board 30 of this embodiment also has four internal wiring layers on which ground wiring layers are formed, as shown in Figure 9. In this embodiment, the frame ground wiring 300 of the third internal wiring layer from the surface side of the printed circuit board 30 extends in the region between the common mode choke coils 130 and 131, in a direction along the substrate surface of the printed circuit board 30, to the location where signal ground wiring 410 formed on the other internal wiring layers exists.

[0070] On the other hand, the signal ground wiring 420, which is formed in the same internal wiring layer as the frame ground wiring 300, is positioned slightly further back towards the communication LSI 110 than the other signal ground wiring 410, maintaining a small gap between it and the frame ground wiring 300. This configuration prevents the frame ground wiring 300 and the signal ground wiring 420 from coming into contact, while the frame ground wiring 300 can almost completely cover the area between the common mode choke coils 130 and 131.

[0071] In this embodiment as well, it is desirable that the frame ground wiring 300 and the signal ground wiring 410 are formed so as not to overlap each other in the thickness direction of the printed circuit board 30. By doing so, it is possible to suppress the inflow of external noise from the frame ground wiring 300 side to the signal ground wiring 410 side due to capacitive coupling.

[0072] Figure 10 is a schematic plan view showing the ground wiring pattern formed on the internal wiring layer of the printed circuit board 30 in the region between the communication LSI 110 and the connector 120 in the fourth embodiment, and Figure 11 is a schematic cross-sectional view of the section D-D of Figure 10 as seen in the direction of the arrow.

[0073] In Figure 10, as with Figure 4, components placed on the surface of the printed circuit board 30 are also shown to facilitate understanding of their positional relationship with the components on the surface of the printed circuit board 30. Also, in Figure 11, as with Figure 5, components other than the communication LSI 110, connector 120, and common mode choke coils 130 and 131 are omitted from the illustration for the sake of simplicity in the explanation. Note that the wiring and component placement on the front and back surfaces of the printed circuit board in this embodiment are the same as in the first embodiment, so Figures 1 to 3 and the explanations based on these drawings can be applied mutatis mutandis, and their explanations are omitted here. Furthermore, in the following, the explanation of parts common to the first embodiment will be omitted, and the explanation will focus on the differences.

[0074] In the third embodiment, the area between the common mode choke coils 130 and 131 is covered by the frame ground wiring 300, but in this embodiment, as shown in Figure 10, the area between the common mode choke coils 130 and 131 is covered by the signal ground wiring 400.

[0075] The printed circuit board 30 of this embodiment also has four internal wiring layers on which ground wiring layers are formed, as shown in Figure 11. In this embodiment, the signal ground wiring 400 of the third internal wiring layer from the surface side of the printed circuit board 30 extends in the region between the common mode choke coils 130 and 131, in a direction along the substrate surface of the printed circuit board 30, to the location where frame ground wiring 310 formed on the other internal wiring layers exists.

[0076] On the other hand, the frame ground wiring 320, which is formed in the same internal wiring layer as the signal ground wiring 400, is positioned slightly further back toward the connector 120 than the other frame ground wirings 310, maintaining a small gap between it and the signal ground wiring 400. This configuration prevents the signal ground wiring 400 from coming into contact with the frame ground wiring 320, while allowing the signal ground wiring 400 to almost completely cover the area between the common mode choke coils 130 and 131.

[0077] Furthermore, it is desirable that the signal ground wiring 400 and the frame ground wiring 310 are formed so as not to overlap each other in the thickness direction of the printed circuit board 30. By doing so, the inflow of external noise from the frame ground wiring 310 to the signal ground wiring 400 due to capacitive coupling can be suppressed.

[0078] In the third and fourth embodiments, as in the second embodiment, components such as the common mode choke coils 130 and 131 can be arranged without interfering with each other, while reducing the mounting area of ​​the required components on one side, and enabling high-density mounting of the connectors 120 with narrower spacing between them. This makes it possible to miniaturize the printed circuit board 30 and, consequently, the in-vehicle control device 10. Furthermore, since the area between the two common mode choke coils 130 and 131 is covered almost without gap by either the frame ground wiring 300 or the signal ground wiring 400, crosstalk noise between the common mode choke coils 130 and 131 can be suppressed more effectively than in the first embodiment.

[0079] According to the embodiments described above, in communication devices such as in-vehicle control devices, it is possible to arrange components such as filters connected between connectors and communication elements on a printed circuit board without interfering with each other, while reducing the area required for component placement on one side of the printed circuit board and increasing the connector mounting density. This makes it possible to miniaturize the printed circuit board and, consequently, the communication device.

[0080] Although the present invention has been described above using representative embodiments as examples, the present invention is not limited thereto and can be implemented in various ways without departing from the spirit of the invention as described in the claims. Furthermore, the embodiments described above are explained in detail for the purpose of clearly illustrating the present invention and are not necessarily limited to those having all the configurations described.

[0081] 10: Base housing, 20: Cover, 30: Printed circuit board, 110, 110a, 110b: Communication LSI, 120, 120a, 120b: Connector, 130, 130a-130d, 131, 131a-131d: Common mode choke coil, 200, 200a-200d, 201, 201a-201d: Signal line pair, 300, 310, 320: Frame ground wiring, 400, 410, 420: Signal ground wiring

Claims

1. A printed circuit board having an internal wiring layer on which a first ground wire and a second ground wire are formed; a connector portion disposed on the printed circuit board to which a plurality of pairs of cables, each transmitting a differential signal, are connected; a communication element disposed on the printed circuit board to process the differential signals transmitted by the plurality of pairs of cables; a first signal line pair formed on one side of the printed circuit board, connecting the connector portion and the communication element, and transmitting a first differential signal among the differential signals transmitted by the plurality of pairs of cables between the connector portion and the communication element; a second signal line pair formed on the other side of the printed circuit board, connecting the connector portion and the communication element, and transmitting a second differential signal, different from the first differential signal among the differential signals transmitted by the plurality of pairs of cables, between the connector portion and the communication element; a first filter provided in the middle of the first signal line pair and disposed on the one side of the printed circuit board, for reducing common-mode noise; A communication device comprising: a second filter provided in the middle of the second signal line pair and positioned on the other surface of the printed circuit board, positioned such that at least a portion of it overlaps with the first filter in the thickness direction of the printed circuit board, for reducing common-mode noise, wherein at least one of the first ground wiring and the second ground wiring extends into the region where the first filter and the second filter overlap in the thickness direction of the printed circuit board, and covers at least a portion of the overlapping region.

2. The communication device according to claim 1, wherein the first ground wire and the second ground wire are physically separated and formed so as not to come into contact with each other.

3. The communication device according to claim 2, wherein at least half of the overlapping region is covered by either the first ground wiring or the second ground wiring.

4. The communication device according to claim 3, wherein the internal wiring layer on which the first ground wiring and the second ground wiring covering the overlapping region are formed is formed in the thickness direction of the printed circuit board at a position closer to an intermediate position in the thickness direction of the printed circuit board than to the one surface and the other surface.

5. A printed circuit board having a plurality of internal wiring layers on which at least one of a first ground wiring and a second ground wiring is formed; a connector portion disposed on the printed circuit board to which a plurality of pairs of cables, each transmitting a differential signal, are connected; a communication element disposed on the printed circuit board to process the differential signals transmitted by the plurality of pairs of cables; a first signal line pair formed on one side of the printed circuit board, connecting the connector portion and the communication element, and transmitting a first differential signal among the differential signals transmitted by the plurality of pairs of cables between the connector portion and the communication element; a second signal line pair formed on the other side of the printed circuit board, connecting the connector portion and the communication element, and transmitting a second differential signal different from the first differential signal among the differential signals transmitted by the plurality of pairs of cables between the connector portion and the communication element; a first filter provided in the middle of the first signal line pair and disposed on the one side of the printed circuit board, for reducing common-mode noise; A communication device comprising: a second filter provided in the middle of the second signal line pair and positioned on the other surface of the printed circuit board, positioned such that at least a portion of it overlaps with the first filter in the thickness direction of the printed circuit board, for reducing common-mode noise, wherein at least one of the plurality of internal wiring layers has at least one of the first ground wiring and the second ground wiring, which extends into the region where the first filter and the second filter overlap in the thickness direction of the printed circuit board and covers at least a portion of the overlapping region.

6. The communication device according to claim 5, wherein at least half of the overlapping region is covered by either the first ground wiring or the second ground wiring formed in at least one of the internal wiring layers.

7. The communication device according to claim 5, wherein one of the first and second ground wirings formed on at least one internal wiring layer extends in a direction along the substrate surface of the printed circuit board to the location where the other ground wiring formed on another of the plurality of internal wiring layers exists, and covers the overlapping region.

8. The communication device according to claim 7, wherein the other ground wiring formed in at least one internal wiring layer is formed at a position set back from the other ground wiring of the other internal wiring layer relative to the first ground wiring, and is formed to be physically separated from the first ground wiring and not to come into contact with each other.

9. The communication device according to claim 8, wherein the one ground wiring formed on at least one internal wiring layer is formed such that it does not overlap with the other ground wiring formed on the other internal wiring layer in the thickness direction of the printed circuit board.

10. The communication device according to claim 5, wherein the plurality of internal wiring layers include a first internal wiring layer having a first ground wiring formed on it that extends within the overlapping region and covers a part of the overlapping region, and a second internal wiring layer having a second ground wiring formed on it that extends within the overlapping region and covers another part of the overlapping region.

11. The communication device according to claim 10, wherein the first ground wiring formed in the first internal wiring layer and the second ground wiring formed in the second internal wiring layer extend to the same position in the overlapping region in the direction along the substrate surface of the printed circuit board.

12. The communication device according to claim 11, wherein the first ground wiring formed in the first internal wiring layer and the second ground wiring formed in the second internal wiring layer are formed so as not to overlap each other in the thickness direction of the printed circuit board.

13. The communication device according to claim 11, wherein the first internal wiring layer and the second internal wiring layer are the two internal wiring layers closest to the midpoint in the thickness direction of the printed circuit board.

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