JP2017034372A - Cable harness device and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive cable harness device maintaining waveform quality of a signal transmitted with a simple configuration and reducing unnecessary radiation.SOLUTION: A cable harness device includes: first and second circuit boards; and a plurality of conductive lines electrically connecting them. On the first circuit board, first and second wiring patterns being a differential signal line pair are electrically connected via a first resistor. On the second circuit board, third and fourth wiring patterns being a differential signal line pair are electrically connected via a second resistor. A combined resistance value when the first and second resistors are connected in parallel is set to be within ±20% of a differential signal output impedance value of an electronic device being mounted onto the first circuit board and outputting a differential signal to the first wiring pattern and the second wiring pattern.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a cable harness device and an electronic apparatus including the cable harness device.

  For example, LVDS (Low Voltage Differential Signaling) and USB (Universal Serial Bus) are known as methods for transmitting digital signals at high speed between a plurality of circuit boards or electronic devices constituting an electronic device. A differential signal line pair is used. The operation signal line pair is configured to transmit a specific transmission line impedance by using two signal line pairs and a ground pattern on the circuit board. For transmission between circuit boards and between electronic devices, two signal line pairs are drawn out as lead wires and transmitted as a cable harness member having a twist structure.

In addition to the cable harness member of this twist structure, as an inexpensive member, for example, an FFC (Flexible Flat Cable) having a structure in which a plurality of conductive lines are supported by an insulating material is used, and disclosed in Patent Document 1 and Patent Document 2. As described above, there has been known a method in which a differential signal line pair is formed as it is in an FFC to transmit and receive differential signals.
For transmission of differential signals using a twisted cable harness member, for example, as in Patent Document 3, in order to reduce unnecessary radiation due to a flowing current, the input side and the output side of the differential signal line pair In both cases, there has been known a differential signal transmission method in which wirings electrically connected to a differential signal line pair are electrically connected via a resistor.

JP 2010-143154 A JP 2013-4506 A Japanese Patent Laying-Open No. 2005-073073

  When handling a differential signal line as described above, it is necessary to first match the differential output impedance of the signal on the electronic device side that transmits the signal with the impedance on the termination side that is set on the electronic device side that receives the signal. is there. This is to reduce reflection loss of a signal to be transmitted and received, and is a so-called impedance matching design. Further, regarding a signal transmission path between electronic devices to be transmitted and received, particularly in a high-frequency signal exceeding 10 MHz, it is necessary to match the impedance of the transmission path with the output impedance of the electronic device on the signal transmission side even in the signal transmission path. . Unless such an impedance matching design is adopted, reflection at each of the connection portion between the input portion of the signal source and the signal transmission path and the connection portion between the signal transmission path and the termination portion serving as a load can be suppressed. It becomes difficult.

  Therefore, in the prior art, the differential transmission path is designed so that the differential output impedance of the electronic device on the signal transmission side is 100Ω and the differential impedance is 100Ω on the mounting substrate. For the cable harness member that electrically connects the circuit boards, a member having a differential signal line impedance of 100Ω is selected, and the terminal resistor serving as a differential load is set to 100Ω in the receiving electronic device. Consistent design was performed.

  However, since the conventional cable harness member purchases a commercially available member whose impedance is controlled with the above-described configuration with respect to the differential signal line, it is easy to be a complicated and expensive member due to the component configuration of the electronic device to be manufactured. In addition, in the configuration such as LVDS, since a plurality of differential signal line pairs such as for clock lines and multi-channel data lines are used, individual-specific cable harness members are often required, which further increases the cost. It was easy.

  In addition, when the cable harness member as described above is applied to transmission / reception of signals between mounting boards in the same electronic device, it is necessary to store the cable harness member in an excess space or a gap of the electronic device. The cable harness member having flexibility is stored by folding the cable harness member. At this time, the cable harness member in which the impedance of the signal line is controlled to a value such as 50Ω or 100Ω is likely to change the impedance of the signal line due to an external shape change such as folding, and the waveform quality of the signal to be transmitted is changed by this impedance change. There was a concern of deterioration.

  The present invention has been made in view of such problems, and the object of the present invention is to provide a simple configuration for a cable harness device that electrically connects between electronic devices and between mounting boards in the electronic devices. Thus, it is an object to provide a cheaper cable harness device that maintains the waveform quality of a signal to be transmitted and reduces unnecessary radiation caused by the cable harness device.

  Application Example 1 A cable harness device including a first circuit board, a second circuit board, and a plurality of conductive lines that electrically connect the first circuit board and the second circuit board. The first conductive line has a differential signal line pair for transmitting a differential signal by the first signal line and the second signal line, and the first conductive line forms a differential signal line pair on the first circuit board. The wiring pattern and the second wiring pattern are electrically connected to one end portions of the first signal line and the second signal line, respectively, and the first wiring pattern and the second wiring pattern are connected to each other. The third wiring pattern and the fourth wiring pattern, which are electrically connected via the resistor and form a differential signal line pair on the second circuit board, are the first signal line and the second signal line. Electrically connected to the other end of the The wiring pattern and the fourth wiring pattern are electrically connected via the second resistor, and the combined resistance value when the first resistor and the second resistor are connected in parallel is the first resistance value. A differential of an electronic device mounted on a first circuit board for supplying a differential signal to the first signal line and the second signal line and outputting the differential signal to the first wiring pattern and the second wiring pattern It is characterized by being set within ± 20% of the signal output impedance value.

  According to this application example, it is possible to provide a cheaper cable harness device that maintains the waveform quality of signals transmitted and received between circuit boards and reduces unnecessary radiation caused by the cable harness device with a simple configuration. Specifically, according to the above configuration, the differential signal output impedance of the electronic device and the impedance on the load side to which the cable harness device is connected are in an impedance matching state. Thereby, while being able to hold | maintain the waveform quality of the signal transmitted / received between mounting boards, the unnecessary radiation resulting from a cable harness apparatus can be reduced.

  Application Example 2 In the cable harness device described in the application example, the signal transmission / reception relationship between the first circuit board and the second circuit board is such that the first circuit board side is the transmission side, The second circuit board side is the receiving side, and the resistance value of the second resistor is set within ± 20% of the differential transmission line impedance value between the first signal line and the second signal line. It is preferable.

  According to this application example, even when a commercially available cable harness member is used, the impedance of the transmission line impedance between the first signal line and the second signal line and the second resistor are designed to be impedance matched. The Thereby, the component reflected by the second resistor in the transmitted differential signal is reduced, the waveform quality of the signal transmitted / received between the mounting boards can be maintained, and unnecessary radiation caused by the cable harness device is reduced. A cheaper cable harness device can be provided.

  Application Example 3 In the cable harness device according to the application example, the length of the cable harness member in the cable harness device is derived from the length of the cable harness member, the transmission time T of the signal to be transmitted, and the signal to be transmitted. It is preferable that the relational expression T> t is satisfied with respect to the transition time t of the voltage level state of the waveform.

  According to this application example, in the case of transmitting a high-frequency signal waveform with a fast rise time, particularly in a differential signal line pair of an electronic device, using a long cable harness device, the quality of the signal waveform is maintained and unnecessary radiation is transmitted. Noise can be reduced.

  Application Example 4 In the cable harness device according to the application example described above, the first circuit board and the second circuit board are mounted on different electronic devices, and signals are transmitted and received between different electronic devices. preferable.

  According to this application example, it is possible to provide a less expensive cable harness device that maintains the waveform quality of signals transmitted and received between electronic devices and reduces unnecessary radiation caused by the cable harness device.

  Application Example 5 In the cable harness device according to the application example described above, it is preferable that the first circuit board and the second circuit board are mounted in the same electronic device, and signals are transmitted and received in the electronic device. .

  According to this application example, a less expensive cable harness that maintains the waveform quality of signals transmitted and received between mounted circuit boards and reduces unnecessary radiation caused by the cable harness device in the same electronic device casing. It is possible to provide a device and contribute to the miniaturization design of electronic equipment.

  Application Example 6 The cable harness device described in the application example preferably includes a plurality of differential signal line pairs.

  According to this application example, it is possible to consolidate the cable harness devices for the electronic equipment to be manufactured, and it is possible to provide an inexpensive cable harness device.

  Application Example 7 In the cable harness device according to the application example described above, the cable harness member has a plurality of conductive lines arranged in parallel in the longitudinal direction of the cable harness member on a tape-like flexible insulating material. preferable.

  According to this application example, it is possible to provide a cable harness device that contributes to miniaturization design for electronic equipment to be manufactured.

  Application Example 8 It is preferable that the electronic device described in the application example includes the cable harness device.

  According to this application example, it is possible to provide an electronic device including a cheaper cable harness device that maintains the waveform quality of signals transmitted and received between boards and reduces unnecessary radiation caused by the cable harness with a simple configuration. .

1 is a schematic configuration diagram of a cable harness device according to Embodiment 1. FIG. The model figure for simulating the waveform quality of a differential signal. The schematic block diagram of FFC. The figure which showed the simulation result of waveform quality. The figure which showed the simulation result of waveform quality. The figure which showed the tendency of unnecessary radiation. The model figure for simulating the waveform quality of the bent FFC. The enlarged view which shows the bending state of bent FFC. The figure which showed the simulation result of the waveform quality of bent FFC.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the scale of each member is made different from the actual scale so that each member can be recognized.

(Embodiment 1)
FIG. 1 is a schematic configuration diagram illustrating the principle of the cable harness device according to the first embodiment. First, a schematic configuration of the cable harness device according to the present embodiment will be described with reference to FIG. In the present embodiment, an example in which two circuit boards are connected using a cable harness device will be described.

  The cable harness device 70 shown in FIG. 1 electrically connects the first circuit board 100 and the second circuit board 200. In FIG. 1, a portion surrounded by a one-dot chain line is a cable harness device 70. The cable harness device 70 includes a cable harness member 10, a resistor 150 on the first circuit board 100, a resistor 250 on the second circuit board 200, and the like.

  The cable harness member 10 has a plurality of conductive lines. The plurality of conductive lines include a ground line 3, a first signal line, and a second signal line. The first signal line is the differential pair line 1, and the second signal line is the differential pair line 2. The differential pair line 1 and the differential pair line 2 form a differential signal line pair.

  One end portions of the differential pair lines 1 and 2 are connected to a wiring pattern 101 as a first wiring pattern and a wiring pattern 102 as a second wiring pattern, respectively, on the circuit board 100. The wiring patterns 101 and 102 are electrically connected to differential signal output ends 111 and 112 of an IC (Integrated Circuit) 110 as an electronic device, which is a differential signal transmission side on the circuit board 100, respectively. Forming a differential pair. The wiring pattern 101 and the wiring pattern 102 forming a differential pair are electrically connected via a resistor 150 as a first resistor.

  The other ends of the differential pair lines 1 and 2 are electrically connected to a wiring pattern 201 as a third wiring pattern and a wiring pattern 202 as a fourth wiring pattern on the circuit board 200, respectively. Yes. The wiring patterns 201 and 202 are electrically connected to the differential signal input terminals 211 and 212 of the IC 210 on the differential signal receiving side on the circuit board 200, respectively, to form a differential pair. . The wiring pattern 201 and the wiring pattern 202 forming a differential pair are electrically connected via a resistor 250 as a second resistor.

  Furthermore, the ground wiring pattern 103 in the first circuit board 100 is used as a ground potential necessary for transmitting and receiving digital differential signals by the ground line 3 of the cable harness member 10 in the second circuit board 200. It is connected to the ground wiring pattern 203.

  At this time, the resistance value (referred to as R2) of the resistor 250 is preferably set to a value equal to the differential impedance set by the differential pair lines 1 and 2 and the ground line 3 of the cable harness member 10. However, since the resistor 250 is set by a normal chip part or the like, the selection is relatively close to the differential impedance value in the E24 system (JIS C 5063). As a guideline, it is preferable to select a value within Z0 ± 20% of the differential impedance value (Z0) while observing actual electrical characteristics. This is based on the simulation results of the inventors. In the first place, the differential impedance value can also be obtained by a method of calculating from the cross-sectional structure of the transmission line or by measurement with a digitizing oscilloscope or the like. However, since it may actually have frequency characteristics, it is practical to provide a width of about ± 20% with respect to the obtained differential impedance value Z0.

  With the above-described configuration, the differential pair lines 1 and 2 and the resistor 250 serving as a terminal resistance thereof are in an impedance matching state. As a result, the signal transmitted through the differential pair lines 1 and 2 can extremely reduce the component reflected by the resistor 250.

Next, the resistance value (R1) of the resistor 150 is set as follows. Since it is necessary to set the impedance value on the output load side to be equal to the output impedance value (Z1) of the signal of the IC 110, the resistance of the resistor 150 to satisfy the following (Equation 1) A value should be set.
1 / Z1 = 1 / R1 + 1 / R2 (Formula 1)

That is, since the combined resistance value of the parallel connection of the resistor 150 and the resistor 250 on the load side is equal to the output impedance value of the signal of the IC 110, all the output signals of the IC 110 can be transmitted to the load side. . Modify both sides of (Equation 1)
Z1 = R1 × R2 / (R1 + R2) (Formula 2)
In this case, the right side of (Equation 2) (the combined resistance value of the resistor 150 and the resistor 250) is designed to have a width of ± 20% with respect to the left side Z1 (the output impedance of the signal of the IC 110). preferable. This is based on the simulation results of the inventors. That is, since the resistance values of R1 and R2 are set from chip resistance components having a constant value such as E24 system, they are set to fall within ± 20% of Z1.

  As a result, the voltage amplitude of the signal output from the IC 110 can be transmitted to the IC 210 side on the receiving side with a minimum loss in the voltage amplitude of the signal.

  Note that the IC 110 and IC 210 in FIG. 1 may have a transmission / reception relationship opposite to the above, and each of the IC 110 and IC 210 may also be used for transmission / reception.

FIG. 2 shows a configuration in which the cable harness device 500 according to the present invention is mounted on a printer. When the cable harness device 500 is mounted on an electronic device, an electromagnetic field simulation was performed in order to examine the state of the waveform quality of the transmitted differential signal. In this electromagnetic field simulation, a printer is used as an example of an electronic device.
Here, the printer 800 is a model in which a metal portion that is mainly electromagnetically affected is extracted, and a main board 300 (a circuit that realizes the function of the printer) as a first circuit board and a second circuit board. As a sub board 600 (LCD: mounted with a display such as Liquid Crystal Display). The cable harness device 500 is mounted to electrically connect the main board 300 and the sub board 600.

A space 1000 in the model of FIG. 2 is an area to be calculated, and the dimensions of each part are as follows. For simplicity, it is composed of copper alone. In the printer 800, the width direction is defined as the X direction, the height direction is defined as the Y direction, and the depth (thickness) direction is defined as the Z direction.
Similarly, the sub-board 600 has an outer shape of 186 mm in the X direction, 55 mm in the Y direction, and 1.6 mm in the Z direction, and is made of copper alone for the sake of simplicity of the model. The main board 300 is mounted on a metal frame 400 (outer shape: 380 mm in the X direction, 74 mm in the Y direction, and 112 mm in the Z direction) made of a steel plate, and is electrically connected to the metal frame 400 with screws 301, 302, and 303. Yes. Further, the cable harness device 500 has one end connected to the connector part 305 of the main board 300 and the other end connected to the connector part 605 of the sub board 600.

  Here, the FFC 50 shown in FIG. 3 was used as the cable harness member of the cable harness device 500. As shown in FIG. 3, the FFC 50 has a plurality of copper conductive lines and an insulating material 57. Line-shaped wirings 51, 52, 53, and 54 are arranged as the plurality of conductive lines. The line-shaped wiring 51 to the line-shaped wiring 54 have a thickness of 0.035 mm, a width of 0.7 mm and a so-called 1 mm pitch with a space between the line-shaped wirings of 0.3 mm with respect to the cross-sectional shape in the width direction. . The insulating material 57 that supports each line-like wiring has a relative dielectric constant of 3.5 and covers each line-like wiring by 0.05 mm in the thickness direction. In addition, although FFC was used as a cable harness member in this embodiment, it is not limited to this. For example, a twisted cable harness may be used.

  The length of the FFC 50 in the longitudinal direction is 236 mm. Here, the line wirings 53 and 54 are ground lines connected to the ground wiring patterns of the main board 300 and the sub board 600, respectively, and are configured to be directly connected to the main board 300 and the sub board 600. The line wirings 51 and 52 are differential pair lines for transmitting a differential signal between the main board 300 and the sub board 600.

<Examination of waveform quality>
In order to examine the waveform quality of the signal transmitted through the FFC 50 for the above configuration, first, between the both ends of the line wirings 51 and 52 of the FFC 50 and the ground wiring patterns of the main board 300 and the sub board 600, respectively. An electromagnetic field simulation was performed by setting a total of four ports for acquiring 1 GHz S-parameters from direct current.

  By the electromagnetic field simulation described above, the 4-port S parameter of the FFC 50 that becomes the cable harness member of the cable harness device 500 is obtained. This is converted into a circuit model for performing circuit simulation such as SPICE (Simulation Program with Integrated Circuit Emphasis) and applied to the circuit simulation of the circuit configuration shown in FIG. Here, the circuit model of the FFC 50 is the cable harness member 10 (FIG. 1) of the cable harness device 70.

  In the FFC 50, the line wirings 53 and 54 are ground lines, and the line wirings 51 and 52 are differential pair lines. Here, the cable harness device 70 of FIG. 1 has one ground line, but the FFC 50 (cable harness device 500) has two ground lines. This is because the cable harness device 70 has been described with a simplified configuration. Actually, a configuration in which differential signal line pairs are arranged between ground lines, such as the FFC 50, is more preferable. Further, when a plurality of differential signal line pairs are provided, a configuration in which a plurality of ground lines are provided and each differential signal line pair is arranged between the ground lines is preferable.

  The differential impedance having the above-described configuration can be calculated by electromagnetic field simulation with respect to the cross-sectional structure in the width direction of the FFC 50, and is about 135Ω. Therefore, if the resistance value (R2) of the resistor 250 in FIG. 1 is 135Ω, the differential impedance of the FFC 50 and the resistor 250 are perfectly impedance matched, but in fact, the resistor 250 is selected from the chip resistor components. R2 = 130 (Ω).

  Next, a circuit model provided from a semiconductor vendor or the like is applied as the circuit model of the differential signal output of the IC 110 on the transmission side in FIG. Specifically, since the output impedance value (Z1) of the differential signal is normally 100Ω, when the resistance value (R1) of the resistor 150 is R1 = 430 (Ω), (Expression 1) is substantially satisfied. be able to. In addition, a circuit model provided from a semiconductor vendor or the like can be applied to the circuit model of the differential signal input of the IC 210 on the receiving side. First, the resistance values R1 and R2 are within a range of ± 20% with respect to the left side (Z1) of (Equation 2), and the resistance value R2 is within ± 20% with respect to the impedance value of the differential line. It is preferable that each chip resistance component is selected so as to be in the above range. This is based on the simulation results of the inventors.

  A signal waveform was simulated by the configuration of the circuit model described above. As a signal to be handled, a differential signal having a voltage amplitude of ± 0.35 V was transmitted at 500 Mbps from the IC 110 on the transmission side. FIG. 4 shows a so-called eye pattern in which the voltage waveform is overwritten in the specific period at the differential signal input terminals 211 and 212 of the receiving side IC 210 at this time. For comparison, FIG. 5 shows an eye pattern of the differential voltage at the differential signal input ends 211 and 212 when the resistor 150 is omitted and the resistor 250 is 100Ω as a conventional configuration. Here, in FIGS. 4 and 5, the horizontal axis represents a specific period of 0 ns to 4 ns (unit: nanosecond), and the vertical axis represents a differential voltage (unit: V).

  In the verification with the eye pattern, it is possible to determine whether the signal quality is good or not by overlaying and displaying rectangular wave waveforms for various bit columns. That is, the higher the degree of rectangular wave overlap, the wider the central area of the waveform (the eye opens), and the better the received signal quality. Conversely, the lower the degree of rectangular wave overlap, the lower the center of the waveform. This means that the area of the part is narrow (the eye is closed), and the received signal quality is poor.

  Comparing FIG. 4 and FIG. 5, it can be seen that the eye pattern (FIG. 4) of the cable harness device 500 is opened by about ± 0.05 V in voltage. That is, the received signal waveform quality is improved compared to the conventional configuration (FIG. 5). Further, with respect to the maximum voltage amplitude on the receiving side, the differential voltage ± 0.35 V is more than ± 0.55 V in the conventional configuration (FIG. 5), whereas the configuration of the present embodiment (FIG. 4). Is ± 0.45 V or less, and the maximum voltage amplitude is suppressed and improved. In addition, it can be seen that the maximum voltage amplitude is large in the conventional configuration and may exceed the allowable voltage level at the input end on the receiving side.

  From the above, the cable harness device 500 can maintain the quality of the signal waveform to be transmitted.

Further, as described above, the length of the FFC 50 is 236 mm. The transmission time T of the signal to be transmitted in the signal line of the FFC 50 (the time for the signal input from one end of the signal line to reach the other end) is about 1 ns depending on the configuration of the FFC 50. At this time, the voltage level transition time (rise time: time from voltage level value change 10% to 90%) (t) in the waveform of the input signal is about 0.7 ns from FIG. 4 and FIG.
T> t (Formula 3)
It has become a relationship. That is, the signal to be transmitted is in a state in which the state transition of the voltage level of the rectangular wave is completed in the transmission path of the FFC 50, which means that there is a potential distribution depending on the wavelength of the signal within the range of the length of the FFC 50. . Therefore, when impedance mismatch occurs at the terminal end of the transmission line, the phenomenon that the voltage at the terminal end becomes higher or lower than the design value becomes remarkable. In order to eliminate this phenomenon, as a high-frequency circuit design concept, the characteristic impedance of the signal transmission path and the impedance of the signal source to be transmitted are made the same, and the resistance (load) at the end of the transmission path is also the same impedance. In order to maintain the signal waveform quality, it is necessary to employ so-called impedance matching.

  According to the cable harness device of the present invention, since the impedance matching described above can be realized, even if the cable harness device is long (T is large), the quality of the signal waveform (t is small) by high-speed data transfer. Can be maintained.

<Examination of unnecessary radiation>
Next, in the printer mounted with the cable harness device of the present invention, a simulation study was performed on the situation of unnecessary radiation. The simulation model examined is substantially the same as that in FIG. 2, but in the connector portion 305 on the main board 300 of the cable harness device 500, a signal source is provided for each signal line of the differential pair of the FFC 50 (each signal source impedance is 50Ω). Of the signal sources, the other of the signal sources is grounded on the main substrate 300 (ground wiring pattern), and the signal phase difference between the signal sources is 180 degrees. Thereby, the output impedance of the signal as the differential signal source can be set to 100Ω. Further, in order to obtain a configuration of a cable harness device that matches the present invention, a 430Ω resistor (R1) is electrically connected between the signal lines of the differential pair of the FFC 50 in the vicinity of the connector portion 305.

  In addition, in the vicinity of the connector portion 605 on the sub-board 600, a 130Ω resistor (R2) is electrically connected between the signal lines to be the differential pair of the FFC 50 in order to obtain a cable harness device conforming to the present invention. . Each signal line that is a differential pair of the FFC 50 is grounded with a load capacitance of 3 pF on the sub-substrate 600 (ground wiring pattern), and a pseudo load of an IC element is attached.

  With respect to the simulation model described above, the radiated electromagnetic field from the printer 800 during operation of the signal source was evaluated as unnecessary radiation. Moreover, it compared with the case of the simulation model which mounted the conventional cable harness apparatus. Specifically, a conventional cable harness device is obtained by omitting the 430Ω resistor and replacing the 130Ω resistor with 100Ω in the simulation model described above. Next, the unnecessary radiation amount (X) in the simulation model to which the cable harness device of the present invention was applied was compared with the unnecessary radiation amount (Y) in the case where the conventional cable harness device was applied. The result is shown in FIG.

FIG. 6 shows the maximum value of the amount of unnecessary radiation radiated from the printer 800 with respect to the input signal source of each frequency. Here, the horizontal axis represents the frequency (unit: MHz) of the input signal source. The vertical axis represents the numerical value obtained by subtracting the unnecessary radiation amount (Y) from the unnecessary radiation amount (X), that is, the difference in electric field strength (unit: dB). Therefore, when the difference in electric field strength is lower than 0 dB (negative value), it is indicated that the level of unnecessary radiation is improved (reduced) by applying the cable harness device 500. As shown in FIG. 6, according to the configuration of the cable harness device 500, it can be seen that unnecessary radiation tends to be improved as compared with the conventional configuration.
This is because the voltage amplitude level of the standing wave generated in the signal line of the differential pair of the FFC 50 is reduced by the configuration of the cable harness device 500. This tendency can also be confirmed from the reduction of the ringing level in the signal waveform of FIG. 4 with respect to FIG.

  As described above, according to the cable harness device 500 of the present embodiment, the following effects can be obtained. That is, it is possible to provide a cable harness device that maintains the waveform quality of signals transmitted and received between boards and reduces the occurrence of unnecessary radiation with a simple and inexpensive configuration.

  Note that the present invention is not limited to the above-described embodiment, and various modifications and improvements can be added to the above-described embodiment. A modification will be described below.

(Modification 1)
In the above embodiment (see FIG. 2), the FFC 50 that electrically connects the main board 300 and the sub board 600 has been described as a substantially linear configuration. However, the present invention is not limited to this configuration, and the FFC is bent. Or may have a curvature. Hereinafter, the FFC 59 having a bend will be described as the cable harness device 501 according to the first modification. In addition, about the component same as Embodiment 1, the same number is attached | subjected and the overlapping description is abbreviate | omitted.

  FIG. 7 is a model diagram of the printer 801 on which the cable harness device 501 is mounted. In the printer 801, the main board 300 and the sub board 600 are electrically connected by the cable harness device 501. The printer 801 has the same configuration as the printer 800 except that the cable harness device 501 is used. Here, the XYZ directions defined in the above-described printer 800 (FIG. 2) are applied to the printer 801 and will be described. That is, the main board 300 and the sub board 600 are opposed to each other in the Z direction, and the cable harness device 501 (FFC 59) extends between the main board 300 and the sub board 600 in the Z direction.

  FIG. 8 is a model diagram showing a state of bending (folding) of the FFC 59 in the cable harness device 501, and an enlarged central portion A of the cable harness device 501 in FIG. As shown in FIG. 8, the FFC 59 has two folds 504 and 505 in the shape of a heel.

  Regarding the foldings 504 and 505, the bent state from the main board 300 toward the sub board 600 will be described. Here, in the X direction (the width direction of the printer 801), the direction toward the outside of the printer 801 is the right side, and the opposite direction is the left side. First, a fold 504 is provided in the approximate center of the FFC 59. The fold 504 has a bend of about 90 degrees to the left. By this folding 504, the extending direction of the FFC 59 is once changed from the Z direction to the X direction (the direction toward the inside of the printer 801). Next, a fold 505 is provided at a position advanced by 60 mm from the fold 504. The fold 505 has a bend of about 90 degrees toward the sub-substrate 600 in the Z direction again. By this folding 505, the FFC 59 is connected again after reaching the sub-board 600 by changing the direction of the extension from the X direction to the Z direction again. Note that the FFC 59 has the same configuration as the FFC 50 described above except that the FFC 59 has foldings 504 and 505.

Regarding the cable harness device 501 including the bent FFC 59 described above, the waveform quality of the differential signal to be transmitted was examined in the same manner as in the above embodiment. The result is shown in FIG.
FIG. 9 is a diagram showing an eye pattern of a differential signal to be transmitted in the cable harness device 501. It can be seen that the signal degradation is small compared to the eye pattern (FIG. 4) in the cable harness device 500. Further, a good level is still maintained with respect to FIG. 5 which is the conventional configuration. As described above, according to the cable harness device 501 according to the present modification, the following effects can be obtained in addition to the effects in the embodiment.
A space for housing and installing the cable harness device is limited, and it is possible to provide an electronic device capable of maintaining the quality of a signal waveform to be transmitted even when the cable harness member (FFC) is bent or curved and mounted.

(Modification 2)
Although the electronic device of the above embodiment has been described by taking a printer as an example, the cable harness device of the present invention is an electronic device having a plurality of circuit boards in a housing or a plurality of electronic devices having circuit boards. Applicable to transmission of differential signals. Accordingly, for example, the cable harness of the above-described embodiment and the modified example is applied to a wearable terminal such as a scanner, a projector, an HMD (Head Mounted Display), a mobile phone, a small information terminal, a game machine, an AV (Audio Visual) device, and a photographing device. An apparatus can be used, and similar effects can be obtained.
As described above, according to the present modification, the effects of the above-described embodiment, that is, a simple and inexpensive configuration, maintaining the waveform quality of a signal to be transmitted and having various effects of reducing unnecessary radiation noise are provided. An electronic device can be provided.

  DESCRIPTION OF SYMBOLS 1, 2 ... Differential pair line, 3 ... Ground line, 10 ... Cable harness member, 50, 59 ... FFC, 70, 500, 501 ... Cable harness apparatus, 100 ... 1st circuit board, 101, 102, 201, 202 ... Wiring pattern, 150, 250 ... Resistor, 200 ... Second circuit board, 800, 801 ... Printer.

Claims (8)

A cable harness device including a first circuit board, a second circuit board, and a plurality of conductive lines that electrically connect the first circuit board and the second circuit board,
The plurality of conductive lines have a differential signal line pair for transmitting a differential signal by a first signal line and a second signal line,
The first wiring pattern and the second wiring pattern forming a differential signal line pair on the first circuit board are electrically connected to one end of the first signal line and the second signal line, respectively. Connected to
The first wiring pattern and the second wiring pattern are electrically connected via a first resistor,
The third wiring pattern and the fourth wiring pattern forming a differential signal line pair on the second circuit board are electrically connected to the other ends of the first signal line and the second signal line, respectively. Connected to
The third wiring pattern and the fourth wiring pattern are electrically connected via a second resistor,
A combined resistance value when the first resistor and the second resistor are connected in parallel is used to supply a differential signal to the first signal line and the second signal line. It is mounted on a circuit board and is set within ± 20% of a differential signal output impedance value of an electronic device that outputs a differential signal to the first wiring pattern and the second wiring pattern, Cable harness device. The signal transmission / reception relationship between the first circuit board and the second circuit board is such that the first circuit board side is a transmitting side, and the second circuit board side is a receiving side,
The resistance value of the second resistor is set within ± 20% of a differential transmission line impedance value between the first signal line and the second signal line. The cable harness device according to 1.   The length of the cable harness member in the cable harness device is derived from the length of the cable harness member, the transmission time T of the signal to be transmitted, and the transition time t of the voltage level state of the waveform that becomes the signal to be transmitted. The cable harness device according to claim 1, wherein a relational expression satisfying T> t is satisfied.   The first circuit board and the second circuit board are mounted on different electronic devices, respectively, and transmit and receive signals between different electronic devices. The cable harness device according to one item.   4. The device according to claim 1, wherein the first circuit board and the second circuit board are mounted in the same electronic device, and transmit and receive signals within the electronic device. 5. The cable harness device according to claim 1.   The cable harness device according to claim 1, comprising a plurality of the differential signal line pairs.   7. The cable harness member according to claim 1, wherein the plurality of conductive lines are juxtaposed in a longitudinal direction of the cable harness member on a flexible insulating material having a tape shape. The cable harness device according to claim 1.   An electronic apparatus comprising the cable harness device according to any one of claims 1 to 7.

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