Communication device

Abstract

The goal is to miniaturize communication devices by avoiding interference between filter components on a printed circuit board while maintaining high-frequency characteristics. [Solution] Multiple differential signal line pairs 200, 201 connecting the communication LSI 110 and the connector 120 are formed distributed on both sides of the printed circuit board 30, and common mode choke coils 130, 131 are provided in the middle of each differential signal line pair. On both sides of the printed circuit board 30, the common mode choke coils 130, 131 are arranged to overlap in the thickness direction of the printed circuit board 30, and at least one of the frame ground wiring 300 and signal ground wiring 400 formed in the internal wiring layer of the printed circuit board 30 is positioned between the common mode choke coils 130, 131.

Description

Technical Field

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

Background Art

[0002] Recently, from the viewpoints of reducing traffic accidents caused by automobiles and lightening the driving operation burden on drivers, the development of autonomous driving systems and the advancement of driving support systems have been rapidly promoted. In recent years, functions such as hands-free that controls the steering of a vehicle without depending on the steering operation by a driver under specific conditions and eyes-free that enables a driver to look away from the driving state have been realized. In-vehicle control devices such as an autonomous driving electronic control unit (AD-ECU) and an advanced driving assistance system electronic control unit (ADAS-ECU) that realize such functions are connected with a number of sensors such as cameras, LiDAR (Light Detection And Ranging), and sonars by cables in order to acquire information from the outside world.

[0003] In addition, while new functions such as connectivity, personalization, and infotainment are being added, the electrical / electronic architecture (E / E architecture) of automobiles is changing to a vehicle-integrated "zone architecture" that integrates the processing of the power train, body domain, and safety domain into the vehicle's central computer. For this reason, a large number of cables are connected to the integrated ECU responsible for the vehicle's central computer for the purpose of backbone transmission with the zone ECUs arranged in each zone within the vehicle.

[0004] As in-vehicle systems become more sophisticated and multi-functional, the amount of data transmitted between ECUs is also increasing, leading to the standardization of in-vehicle networks that enable transmission speeds of Gbps or more. Furthermore, standardization is progressing for differential transmission of high-speed signals exceeding Gbps using twisted-pair cables in communication with sensors, primarily cameras. In addition, these standards are also advancing the standardization of a power-over-data line (PoDL) technology, which superimposes power onto the data transmission cable to reduce the weight of the harness.

[0005] This trend towards higher network speeds is progressing not only in automotive control systems but also in communication devices across various fields. In high-speed networks, the current spectrum used for data transmission exists at a large level in the region exceeding GHz, necessitating the suppression of electromagnetic wave radiation in the high-frequency band. Furthermore, since elements such as communication LSIs process signals up to the GHz band, it is also necessary to suppress the interference of GHz-band noise.

[0006] In such high-speed data transmission, for example, Patent Document 1 discloses a printed circuit board that cancels common-mode noise transmitted on a differential signal line pair using a common-mode filter. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2015-231006 [Overview of the project] [Problems that the invention aims to solve]

[0008] Some communication devices, such as the aforementioned AD / ADAS-ECUs and integrated ECUs used in automobiles, require miniaturization due to space constraints. As the number of cables connected to the communication device increases, the number of common-mode filters provided on the printed circuit board also increases. Therefore, when attempting to connect more cables using multiple connectors, it becomes necessary to widen the spacing between connectors to avoid interference between the filter components that make up the common-mode filters, which presents a challenge in miniaturizing the enclosure.

[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 distance between connectors while avoiding interference between filter components on the printed circuit board. [Means for solving the problem]

[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 for transmitting a second differential signal different from a first differential signal between a connector and a 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 multiple 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. [Effects of the Invention]

[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. [Brief explanation of the drawing]

[0013] [Figure 1] 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. [Figure 2] This is a schematic view of a portion of the connection area between the communication LSI and the connector on a printed circuit board, as seen from the surface. [Figure 3] This is a schematic view of a portion of the connection area between the communication LSI and the connector on a printed circuit board, seen from the back. [Figure 4] This is a schematic diagram showing an example of ground wiring formed in the internal wiring layer of a printed circuit board in the region between the communication LSI and the connector. [Figure 5] This is a schematic cross-sectional view of the area indicated by the dashed line AA in Figure 4, viewed in the direction of the arrow. [Figure 6] This is a schematic plan view showing an example of ground wiring formed in the internal wiring layer of a printed circuit board in the second embodiment. [Figure 7] This is a schematic cross-sectional view of the area BB shown by the dashed line in Figure 6, viewed in the direction of the arrow. [Figure 8] This is a schematic plan view showing an example of ground wiring formed in the internal wiring layer of a printed circuit board in the third embodiment. [Figure 9] This is a schematic cross-sectional view of the area CC shown by the dashed line in Figure 8, viewed in the direction of the arrow. [Figure 10] This is a schematic plan view showing an example of ground wiring formed in the internal wiring layer of a printed circuit board in the fourth embodiment. [Figure 11] This is a schematic cross-sectional view of the area indicated by the dashed line DD in Figure 10, viewed in the direction of the arrow. [Modes for carrying out the invention]

[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 examples for explaining the present invention, and for the sake of clarity of explanation, appropriate omissions or simplifications have been made. Also, for the sake of easy understanding of the invention, note that the positions, sizes, shapes, ranges, etc. of the respective components shown in the drawings may not necessarily represent them accurately.

[0015] FIG. 1 is an exploded perspective view schematically showing the configuration in an 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 automatic driving or supports a driver's driving operation while communicating with a plurality of sensing devices and various control units that control devices such as an engine, brakes, and steering, or may be an integrated ECU that aggregates and integrates information from zone ECUs arranged at various parts of the vehicle for integrated control. Here, a control device that is mounted on a vehicle and in which a plurality of devices and apparatuses are connected via a network to perform processing for realizing various functions is collectively referred to as an in-vehicle control device, such as these devices.

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

[0018] The printed circuit board 30 is provided with a microcontroller unit (MCU) 100 that constitutes the in-vehicle control device, a plurality of communication LSIs 110, and a plurality of connectors 120 to which cables for connecting to a network 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 unit.

[0020] The printed circuit board 30 has a connector section on its outer edge, to which multiple 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 one 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 sends them, and also converts data signals received 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 on 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 distinguish between them and they are described in general terms, the alphabetical subscript will be omitted. 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.

[0024] The connector 120 is a multi-pin connector capable of connecting four pairs of cables, and has four sets of eight connection terminals, each capable of connecting four pairs of signal lines 200. 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.

[0025] 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.

[0026] Common mode choke coils 130a, 130b, 130c, and 140d 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] Please note that in Figure 2, for the sake of clarity, frame ground wiring, signal ground wiring, circuit components other than those mentioned above, signal wiring connecting them, and power supply wiring are omitted from the illustration.

[0031] Figure 3 is a schematic view of a portion of the connection area between the communication LSI 110 and the connector 120 on the printed circuit board 30, as seen from the back.

[0032] Figure 3 shows the back surface of the printed circuit board 30 corresponding to the portion shown in Figure 2, with the communication LSIs 110a and 110b and connectors 120a and 120b located on the front surface of the printed circuit board 30 indicated by dashed lines.

[0033] The input / output terminals of communication LSIs 110a and 110b are connected to via 210, and via 220 is connected to the connector terminals, via signal line pairs 201a, 201b, 201c, and 201d.

[0034] Common mode choke coils 131a, 131b, 131c, and 131d are connected to 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).

[0035] 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.

[0036] Furthermore, similar to the signal line pair 200, each signal line constituting the signal line pair 201 is connected to the ground wiring, with a termination component consisting of a resistor 151 and a capacitor 161 connected in series, and an ESD element 171 protecting the circuit from surge voltages such as static electricity. These ground wiring terminals are connected to the frame ground wiring formed on the back surface, and / or to the frame ground wiring formed in the internal wiring layer of the printed circuit board 30 via vias 230 and 240.

[0037] The coupling capacitor 141, the termination components (resistor 151 and capacitor 161), and the ESD element 171 are arranged to overlap almost completely with the coupling capacitor 140, resistor 150, capacitor 160, and ESD element 170 located on the surface of the printed circuit board 30 in the thickness direction, similar to the common mode choke coil. This allows vias 230 and 240 to be easily shared between components located on the surface and components located 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.

[0038] It should be noted that 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.

[0039] Figure 4 is a schematic diagram showing an example of a 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. 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.

[0040] 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.

[0041] 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.

[0042] Near the area where the common mode choke coil 130 is located, the frame ground wiring 300 protrudes toward the signal ground wiring 400, covering approximately half of the area between the common mode choke coil 130 and the common mode choke coil 131. Similarly, the signal ground wiring 400 protrudes toward the frame ground wiring 300, covering approximately the remaining half of the area 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, creating an area within the region between the common mode choke coil 130 and the common mode choke coil 131 where neither the frame ground wiring 300 nor the signal ground wiring 400 is present.

[0043] Figure 5 is a schematic cross-sectional view of the portion indicated by the dashed line AA in Figure 4, viewed in the direction of the arrow. In Figure 5, components other than the communication LSI 110a, connector 120a, and common mode choke coils 130b and 131b are omitted from the illustration for the sake of simplicity. Also, Figure 5 shows the internal wiring layer between common mode choke coil 130b and common mode choke coil 131b, but the following explanation is also common to the internal wiring layer between the other common mode choke coils 130. For this reason, the subscripts attached to the reference numbers indicating each part will be omitted in the following explanation.

[0044] 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 so that at least a portion of them overlap each other in the thickness direction of the printed circuit board 30.

[0045] The printed circuit board 30 has multiple internal wiring layers in which frame ground wiring 300, 310 and signal ground wiring 400, 410 are formed. Although only the internal wiring layers in which ground wiring is formed are shown here, the printed circuit board 30 may also have internal wiring layers in which signal wiring is formed.

[0046] Of the multiple internal wiring layers on which ground wiring is formed, the frame ground wiring 300 and signal ground wiring 400, which are formed on the internal wiring layer located in the middle of 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 Figure 4. The frame ground wiring 300 and the signal ground wiring 400 are formed with a gap between them so that they are physically separated and do not come into contact with each other.

[0047] The frame ground wiring 310 formed on the other internal wiring layer is formed from the connector 120 side end of the common mode choke coils 130 and 131 toward the connector 120, and does not extend in the direction of the region between the common mode choke coil 130 and the common mode choke coil 131. Similarly, the signal ground wiring 410 formed on the other internal wiring layer is formed from the communication LSI 110 side end of the common mode choke coils 130 and 131 toward the communication LSI 110, and does not extend in the direction of the region between the common mode choke coil 130 and the common mode choke coil 131.

[0048] Common mode choke coils 130 and 131 are typically placed between the frame ground wiring and the signal ground wiring. In this embodiment, when the common mode choke coil 130, which is placed on the front surface of the printed circuit board 30, and the common mode choke coil 131, which is placed on the back surface, are positioned in a location that overlaps in the thickness direction of the printed circuit board 30, the distance between the common mode chokes becomes small, which may cause crosstalk noise due to electromagnetic interference between them. In this embodiment, the generation of crosstalk noise is suppressed 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, which are placed on the front and back surfaces of the printed circuit board 30, overlap in the thickness direction of the printed circuit board 30.

[0049] It is desirable that the gap between the frame ground wiring 300 and the signal ground wiring 400 be small. For example, to reduce the generation of crosstalk noise by more than half, it is desirable that more than half of the overlapping area of ​​the common mode choke coils 130 and 131 be covered by the frame ground wiring 300 or the signal ground wiring 400.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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 dashed-dotted line BB section of Figure 6, viewed in the direction of the arrow.

[0055] 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 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.

[0056] 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 almost entirely covered by either the frame ground wiring 300 or the signal ground wiring 400, as shown in Figure 6.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] Note that, in addition to the frame ground wiring 300 and signal ground wiring 400, the frame ground wiring 310 and signal ground wiring 410 are formed up to near 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.

[0062] 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.

[0063] Furthermore, since the area between the two common-mode choke coils 130 and 131 is almost completely covered 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 compared to the first embodiment.

[0064] 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 CC section of Figure 8 as seen in the direction of the arrow.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] On the other hand, the signal ground wiring 420, which is formed on 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.

[0069] 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.

[0070] 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 dashed-dotted line DD section of Figure 10, viewed in the direction of the arrow.

[0071] 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. Furthermore, 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. 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; therefore, Figures 1 to 3 and their corresponding explanations can be applied mutatis mutandis, and their explanations are omitted here. In the following, explanations of parts common to the first embodiment will be omitted, and the focus will be on the differences.

[0072] 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.

[0073] 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.

[0074] 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 towards 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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. [Explanation of symbols]

[0079] 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 section is arranged on the aforementioned printed circuit board, to which multiple pairs of cables, each transmitting differential signals, are connected. A communication element arranged on the printed circuit board and processing the differential signal transmitted by the multiple pairs of paired cables, A first signal line pair formed on one side of the printed circuit board connects the connector portion and the communication element, and transmits a first differential signal among the multiple pairs of paired cables between the connector portion and the communication element, A second signal line pair formed on the other side of the printed circuit board connects the connector portion and the communication element, and transmits a second differential signal, which is different from the first differential signal among the differential signals transmitted by the plurality of pair cables, between the connector portion and the communication element. A first filter is provided in the middle of the first signal line pair and is positioned on one side of the printed circuit board to reduce common-mode noise, The system includes a second filter provided in the middle of the second signal line pair and positioned on the other side of the printed circuit board, 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, A communication device in which at least one of the first ground wiring and the second ground wiring extends within a 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 wire and a second ground wire is formed, A connector section is arranged on the aforementioned printed circuit board, to which multiple pairs of cables, each transmitting differential signals, are connected. A communication element arranged on the printed circuit board and processing the differential signal transmitted by the multiple pairs of paired cables, A first signal line pair formed on one side of the printed circuit board connects the connector portion and the communication element, and transmits a first differential signal among the multiple pairs of paired cables between the connector portion and the communication element, A second signal line pair formed on the other side of the printed circuit board connects the connector portion and the communication element, and transmits a second differential signal, which is different from the first differential signal among the differential signals transmitted by the plurality of pair cables, between the connector portion and the communication element. A first filter is provided in the middle of the first signal line pair and is positioned on one side of the printed circuit board to reduce common-mode noise, The system includes a second filter provided in the middle of the second signal line pair and positioned on the other side of the printed circuit board, 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, A communication device having at least one of the first ground wiring and the second ground wiring, wherein at least one of the plurality of internal wiring layers is an internal wiring layer that extends within a 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 ground wiring and the second ground wiring 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 the 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 one ground wiring, and is formed to be physically separated from the one 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 the 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 a 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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