JP2015136277A - Circuit device, circuit board and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit device, a circuit board and an electronic apparatus which can detect a chopping current with high accuracy.SOLUTION: A circuit device 200 comprises: a bridge circuit 210 including transistors Q1, Q2 on a high side and transistors Q3, Q4 on a low side; a first terminal SN1 for connecting a current Id passing through the bridge circuit 210 to one end of a sense resistor 290; a second terminal SN2 for connecting the current Id to the other end of the sense resistor 290; and a third terminal RNF connected on a source side of the transistors Q3, Q4 on the low side.

Description

  The present invention relates to a circuit device, a circuit board, an electronic device, and the like.

  As a method for controlling the drive current of a DC motor, a method for controlling a chopping current is known. In this method, a sense resistor is connected to an H bridge circuit, and a voltage at one end of the sense resistor (a node connected to the H bridge side) is compared with a reference voltage that defines a chopping current by a comparator. Based on the comparison result, the chopping current is controlled by switching from the charge period to the decay period.

JP 2010-12873 A

  Since the motor drive current flows through the sense resistor, power is consumed. However, since the power is not used for driving the motor, a loss occurs, which causes a reduction in power efficiency. Therefore, it is desirable to reduce the sense resistance. However, when the sense resistance value decreases, for example, the voltage drop caused by the parasitic resistance of the wiring becomes relatively large as an error component with respect to the potential difference between both ends of the sense resistor, so an error occurs in the detected value of the chopping current, There is a problem that errors occur in the rotational speed and torque of the motor.

  Patent Document 1 discloses a control device for an electric power steering device that detects a voltage across a sense resistor and detects whether the current detection circuit is in a normal state or an abnormal state based on the voltage. ing. However, this method detects normal / abnormal conditions, and there is no disclosure of the above problems.

  According to some aspects of the present invention, it is possible to provide a circuit device, a circuit board, an electronic device, and the like that can detect a chopping current with high accuracy.

  One embodiment of the present invention includes a bridge circuit having a high-side transistor and a low-side transistor, a first terminal connected to one end of a sense resistor for detecting a current flowing in the bridge circuit, The present invention relates to a circuit device including a second terminal for connecting to the other end of the sense resistor and a third terminal connected to the source side of the low-side transistor.

  According to one embodiment of the present invention, one end of the sense resistor is connected to the first terminal, the other end of the sense resistor is connected to the second terminal, and the third terminal is a transistor on the low side of the bridge circuit. Connected to the source side. Thus, by providing the first terminal, the second terminal, and the third terminal in the circuit device, it becomes possible to detect the chopping current with high accuracy.

  In one embodiment of the present invention, charging is performed by detecting a voltage difference between a first voltage that is the voltage at the one end of the sense resistor and a second voltage that is the voltage at the other end of the sense resistor. A detection circuit that detects a charge current in a period, and a control circuit that performs on / off control of the high-side transistor and the low-side transistor based on a detection result of the detection circuit, 1 terminal is connected to a first input node of the detection circuit, the second terminal is connected to a second input node of the detection circuit, and the third terminal is connected to the detection circuit via a wiring. It may be a terminal for connecting to the one end of the sense resistor.

  By providing the first terminal and the second terminal for inputting the voltage across the sense resistor, the voltage across the sense resistor is different from the current path passing through the sense resistor from the third terminal. Can be input to the detection circuit. Since the voltage difference between both ends of this sense resistor is not affected by the parasitic resistance existing in the current path, the detection error of the chopping current can be reduced by detecting the voltage difference with the detection circuit.

  In the aspect of the invention, the distance between the third terminal and the bridge circuit may be shorter than the distance between the first terminal and the bridge circuit and the distance between the second terminal and the bridge circuit. .

  The transistor of the bridge circuit has a parasitic diode between the drain and the substrate of the circuit device, and current flows through the substrate through the parasitic diode during the decay period, the substrate potential fluctuates, and the detection accuracy of the chopping current is improved. Reduce. In this respect, according to one embodiment of the present invention, since the first terminal and the second terminal connected to the detection circuit can be arranged apart from the bridge circuit, the influence of the fluctuation of the substrate potential can be reduced, and the chopping current can be reduced. Detection accuracy can be improved.

  In one embodiment of the present invention, the distance between the first terminal and the detection circuit and the distance between the second terminal and the detection circuit may be shorter than the distance between the third terminal and the detection circuit. .

  In this case, since the detection circuit can be arranged away from the third terminal connected to the bridge circuit, the influence of the fluctuation of the substrate potential as described above can be reduced, and the detection accuracy of the chopping current can be improved.

  In one embodiment of the present invention, the first terminal and the second terminal are disposed on a first side of the circuit device, and the third terminal is disposed on a second side of the circuit device. May be.

  In this way, by arranging the first terminal, the second terminal, and the third terminal on different sides, the distance between the first terminal, the second terminal, and the third terminal can be increased. Accordingly, the distance between the bridge circuit connected to them and the detection circuit can be increased.

  In one embodiment of the present invention, a ground terminal connected to a substrate of the circuit device is included, and the distance between the ground terminal and the first terminal and the distance between the ground terminal and the second terminal are the ground terminal. And may be shorter than the distance between the third terminals.

  The current flowing from the parasitic diode of the bridge circuit to the substrate flows to the ground terminal connected to the substrate. According to one embodiment of the present invention, since the ground terminal can be arranged away from the bridge circuit, the substrate resistance to the ground terminal can be increased. This makes it difficult for current to flow from the parasitic diode to the substrate, so that fluctuations in the substrate potential can be reduced.

  In one embodiment of the present invention, a pre-driver that drives the bridge circuit based on the on / off control signal is included, wherein the first terminal and the second terminal are a first side of the circuit device. The third terminal is disposed on the second side of the circuit device, and the direction from the second side to the third side opposite to the second side is defined as the first direction. In this case, the pre-driver may be disposed on the first direction side of the bridge circuit, and the detection circuit may be disposed on the first direction side of the pre-driver.

  In this way, the bridge circuit can be disposed on the second side where the third terminal is disposed, and the pre-driver and the detection circuit can be disposed along the first direction. The first terminal and the second terminal can be connected to the detection circuit from the first side. With such an arrangement, the bridge circuit and the detection circuit can be arranged apart from each other.

  In one embodiment of the present invention, the detection circuit differentially amplifies the first voltage input to the first input node and the second voltage input to the second input node. A differential amplifier circuit may be included.

  In this way, it is possible to detect the chopping current by amplifying the voltage difference between both ends of the sense resistor with the differential amplifier circuit and comparing the voltage with the reference voltage. Since the differentially amplified voltage is not affected by the parasitic resistance as described above, the detection error of the chopping current can be reduced.

  According to another aspect of the present invention, there is provided a circuit board on which any one of the circuit devices described above is mounted, and a first wiring that connects the first terminal and the one end of the sense resistor. A circuit board including: a second wiring that connects the second terminal and the other end of the sense resistor; and a third wiring that connects the third terminal and the one end of the sense resistor. Related to.

  In this way, the voltage at both ends of the sense resistor can be input to the first and second terminals by the first and second wires different from the third wire through which the current from the bridge circuit to the sense resistor flows. Thereby, the voltage across the sense resistor can be detected without being affected by the parasitic resistance generated in the third wiring.

  Still another embodiment of the present invention relates to an electronic device including any one of the circuit devices described above.

The circuit apparatus of a comparative example. Operation | movement explanatory drawing of the circuit apparatus of a comparative example. 1 is a configuration example of a circuit device and a circuit board according to the present embodiment. 3 shows a detailed configuration example of a differential amplifier circuit. An example of a cross-sectional structure of an N-type transistor having a DMOS structure. 4 is a layout configuration example of the circuit device according to the present embodiment. The waveform which measured the voltage of the one end of the sense resistance in a comparative example, and the voltage difference of the both ends of the sense resistance in this embodiment. Deviation of chopping current measured at each set value of the D / A converter circuit. 1 is a configuration example of an electronic apparatus according to an embodiment.

  Hereinafter, preferred embodiments of the present invention will be described in detail. The present embodiment described below does not unduly limit the contents of the present invention described in the claims, and all the configurations described in the present embodiment are indispensable as means for solving the present invention. Not necessarily.

1. Comparative Example FIG. 1 shows a circuit device of a comparative example. The circuit device 200 includes a bridge circuit 210 that supplies a drive current to a motor 280 (for example, a DC motor or a stepping motor), a control circuit 240 that outputs a PWM signal to the bridge circuit 210, and a pre-driver that buffers the PWM signal. 260 and a detection circuit 250 that detects a voltage VS at one end of the sense resistor 290. The detection circuit 250 includes a D / A conversion circuit 230 that outputs a reference voltage VR, and a comparator 221 that compares the reference voltage VR and the voltage VS at one end of the sense resistor 290.

  The operation of the circuit device 200 will be described with reference to FIG. In the charging period TC, the transistors Q1 and Q4 of the bridge circuit 210 are turned on, and the transistors Q2 and Q3 are turned off. At this time, since the current Id (charge current) flowing through the motor 280 increases, the voltage VS increases. The comparator 221 detects that the voltage VS has reached the reference voltage VR and activates the signal CQ1, and the control circuit 240 receives the activated signal CQ1 and switches from the charge period TC to the decay period TD. A current when the voltage VS reaches the reference voltage VR is referred to as a chopping current IL.

  In the decay period TD, the transistors Q2 and Q3 of the bridge circuit 210 are turned on and the transistors Q1 and Q4 are turned off. At this time, the current Id (decay current) flowing through the motor 280 decreases. For example, the elapse of a predetermined time is counted by a counter, and the decay period TD is switched to the charge period TC.

  In this way, the current flowing through the motor 280 rises and falls with the chopping current IL as the upper limit, and the average becomes the drive current of the motor 280. Since the chopping current is determined by the reference voltage VR, the drive current can be set by changing the reference voltage VR, and the rotation speed and torque of the motor 280 can be controlled.

Now, the voltage VS at one end of the sense resistor 290 when the chopping current IL is flowing can be expressed by the following equation (1).
VS = Rs · IL + Rp · IL (1)

  Here, Rs is the resistance value of the sense resistor 290, and Rp is the resistance value of the parasitic resistors Rp1 and Rp2 generated in the current path of the drive current.

  The circuit device 200 is composed of, for example, an IC chip (integrated circuit device), and the terminals of the circuit device 200 correspond to terminals of a package of the IC chip or pads on a silicon substrate. The circuit board 200, which is an IC chip, is mounted on a printed board. The sense resistor 290 is mounted on the printed board as a circuit component. In this case, as the parasitic resistances Rp1 and Rp2, for example, the resistance of the lead wire of the terminal RNF of the circuit device 200, the contact resistance of soldering, the wiring resistance of the printed board on which the circuit device 200 is mounted, and the like are assumed.

  For example, considering the charge period, heat is generated by the on-resistances of the transistors Q1 and Q4 and the sense resistor 290, resulting in power loss. In particular, the sense resistor 290 is provided for current control, and there is a problem that it is desired to reduce the resistance value as much as possible to reduce the power loss.

  However, as can be seen from the above equation (1), when the resistance value Rs of the sense resistor 290 is decreased, the error Rp · IL of the voltage VS due to the parasitic resistance is relatively increased. Since the chopping current IL is detected when VS = VR, if the error Rp · IL increases, the chopping current IL has a large error from the desired current value IL = VR / Rs, and the motor 280 Torque is inaccurate. Since the resistance value Rp of the parasitic resistance depends on the wiring pattern of the printed circuit board and the like, the resistance value Rp is not determined unless the circuit device 200 is actually mounted. It is difficult to reduce the resistance value Rs from the viewpoint of detection accuracy.

2. Circuit Device and Circuit Board FIG. 3 shows a configuration example of a circuit device and a circuit board according to this embodiment that can solve the above-described problems. The circuit device 200 (for example, an integrated circuit device) includes a bridge circuit 210, a control circuit 240, a detection circuit 250, a pre-driver 260, a first terminal SN1, a second terminal SN2, and a third terminal RNF. In addition, the same code | symbol is attached | subjected about the component same as the component demonstrated in FIG. 1, and description is abbreviate | omitted suitably.

  The bridge circuit 210 includes high-side transistors Q1 and Q2 and low-side transistors Q3 and Q4. The third terminal RNF is connected to the source side of the low-side transistors Q3 and Q4.

  Specifically, the transistors Q1 to Q4 are MOS transistors configured in an H bridge. The high-side transistors Q1 and Q2 are P-type transistors, for example, and are connected to the high potential power supply side rather than the low-side transistors. The low-side transistors Q3 and Q4 are N-type transistors, for example, and are connected to the low-potential power supply side rather than the high-side transistors.

  More specifically, the source nodes of the high-side transistors Q1 and Q2 are connected to the node of the power supply voltage VCC, and the source nodes of the low-side transistors Q3 and Q4 are connected to the third terminal RNF. To the node N1. One end of a sense resistor 290 is connected to the third terminal RNF. The drain nodes of the transistors Q1 and Q3 are connected to a terminal OUT1 to which one end of the motor 280 is connected. The drain nodes of the transistors Q2 and Q4 are connected to a terminal OUT2 to which the other end of the motor 280 is connected.

  The transistors Q1 to Q4 include parasitic diodes D1 to D4 configured by a MOS structure, which are connected in parallel to the transistors Q1 to Q4.

  Here, all of the transistors Q1 to Q4 may be composed of N-type MOS transistors. Alternatively, the transistors Q1 to Q4 may be configured with bipolar transistors. In this case, the diodes D1 to D4 are not parasitic diodes but circuit elements.

  The first terminal SN1 is connected to one end of a sense resistor 290 for detecting a current Id flowing through the bridge circuit 210. The second terminal SN2 is connected to the other end of the sense resistor 290.

  Specifically, the sense resistor 290 has a terminal TR1 at one end and a terminal TR2 at the other end. The sense resistor 290 is generally a component provided outside the circuit device 200. The terminals TR1 and TR2 correspond to terminals at both ends of a resistance element as a component, for example. The circuit device 200 and the sense resistor 290 are mounted on a circuit board. A first wiring L1 that connects the terminal TR1 and the first terminal SN1 and a second wiring L2 that connects the terminal TR2 and the second terminal SN2 are arranged on the circuit board. In addition to the wirings L1 and L2, the circuit board includes a third wiring L3 that connects the terminal TR1 and the third terminal RNF, a fourth wiring L4 that connects the terminal TR2 and a ground voltage node, Is placed.

  In this manner, the voltage across the sense resistor 290 is input to the first terminal SN1 and the second terminal SN2 by dividing the wiring, so that the current path from the bridge circuit 210 to the ground voltage and the sense resistor 290 The voltage path for taking out the voltage at both ends can be separated. As a result, even when a voltage drop due to the parasitic resistance as in the second term on the right side of the above equation (1) occurs in the current path, the voltage difference between the first terminal SN1 and the second terminal SN2 Is determined only by the voltage difference across the sense resistor 290. Therefore, by detecting the voltage difference, the chopping current IL can be accurately detected, and the chopping current can be accurately detected even if the resistance value of the sense resistor 290 is reduced.

  Next, the detection circuit 250 that detects a voltage difference between the first terminal SN1 and the second terminal SN2 will be described.

  The first input node NI1 of the detection circuit 250 is connected to the first terminal SN1, and the second input node NI2 of the detection circuit 250 is connected to the second terminal SN2. Then, the detection circuit 250 detects a charge current flowing through the motor 280 during the charge period by detecting a voltage difference between the input nodes NI1 and NI2.

  Specifically, the detection circuit 250 includes a comparator 221, a D / A conversion circuit 230, and a differential amplifier circuit 270.

  The first input node NI1 is, for example, a positive input node of the differential amplifier circuit 270, and the second input node NI2 is, for example, a negative input node of the differential amplifier circuit 270. Then, differential amplifier circuit 270 differentially amplifies the voltages at these nodes and outputs voltage VQ.

  The D / A conversion circuit 230 converts a code (information, digital data) specifying the current value of the chopping current into an analog reference voltage VR. For example, the D / A conversion circuit 230 includes a ladder resistor, and a code corresponds to each tap of the ladder resistor. The code is written in, for example, a register (not shown) from an external host (for example, a CPU), and a reference voltage VR corresponding to the code is output.

  The comparator 221 compares the voltage VQ with the reference voltage VR. When the voltage VQ exceeds the reference voltage VR, the comparator 221 changes the output signal CQ1 from inactive (for example, H level) to active (for example, L level).

  The control circuit 240 performs on / off control of the high-side transistors Q1 and Q2 and the low-side transistors Q3 and Q4 based on the detection result of the detection circuit 250. That is, when the output signal CQ1 of the comparator 221 becomes active, the charge period is switched to the decay period, the control signal (PWM signal) for turning off the transistors Q1 and Q4 and the control signal (PWM signal for turning on the transistors Q2 and Q3). ) Is output. The pre-driver 260 includes buffers 261 to 264. These buffers 261 to 264 buffer control signals and supply drive signals G1 to G4 to the gates of the transistors Q1 to Q4.

  As described above, the differential amplifier circuit 270 amplifies the voltage difference between the first terminal SN1 and the second terminal SN2, so that the voltage difference between both ends of the sense resistor 290 can be output as the voltage VQ. Since this voltage VQ is not affected by the parasitic resistance, it is a desired voltage determined by the resistance value of the sense resistor 290. Then, by comparing the voltage VQ with the reference voltage VR, the chopping current IL becomes an accurate current value corresponding to the reference voltage VR, and the torque of the motor 280 specified by the code of the D / A conversion circuit 230 is accurately realized. Is done.

3. Differential Amplifier Circuit FIG. 4 shows a detailed configuration example of the differential amplifier circuit 270 described above. Differential amplifier circuit 270 includes an operational amplifier 271 and resistance elements 272 to 275.

  The resistance element 272 is provided between the first input node NI1 and the inverting input terminal of the operational amplifier 271. Resistance element 273 is provided between output node NQ and the inverting input terminal of operational amplifier 271. The resistance element 274 is provided between the second input node NI2 and the non-inverting input terminal of the operational amplifier 271. The resistance element 275 is provided between the node of the ground voltage and the non-inverting input terminal of the operational amplifier 271.

  The resistance values of the resistance elements 272 and 274 are R1, and the resistance values of the resistance elements 273 and 275 are R2. In this case, the output voltage VQ = (R2 / R1) · (VI2-VI1) is output to the output node NQ. The resistance value R1 and the resistance value R2 may be the same or different.

4). Layout In the comparative example of FIG. 1, the cause of the detection error of the chopping current is a parasitic diode in the transistor of the bridge circuit 210 in addition to the parasitic resistance. This will be described below.

  FIG. 5 shows an example of a cross-sectional structure of the transistor Q3 (or Q4). In this example, an N-type transistor Q3 having a DMOS (Double-Diffused MOSFET) structure is formed on a P-type silicon substrate.

  Specifically, an N-type buried layer (NBLA) is formed on a P-type substrate (Psub), a P-type epitaxial layer is formed on the buried layer, and an N-type well (NNLC) is formed in the epitaxial layer. . An N type diffusion layer is formed on the N type well to form a drain. Further, a P-type well (PBDA) is formed on the N-type well, and an N-type diffusion layer is formed on the P-type well to form a source.

  The P-type substrate is connected to the ground terminal AGND of FIG. 1, and the drain is connected to the output terminal OUT1 to the motor 280. Since the drain is in contact with the P-type substrate through the N-type layer (NWLC, NBLA), a parasitic diode Dp1 is generated between the drain and the P-type substrate. In the decay period, the transistors Q2 and Q3 are turned on, and a regenerative current flows from the ground toward the power source. At this time, the output terminal OUT1 has a negative potential lower than the ground voltage. Therefore, a forward voltage is applied to the parasitic diode Dp1, and a current flows from the ground terminal AGND to the drain via the P-type substrate.

  As shown in FIG. 1, since the P-type substrate has a substrate resistance Rsub (parasitic resistance), the substrate potential fluctuates when a current flows from the ground terminal AGND to the drain. Due to this fluctuation, the detection circuit 250 is affected, and the reference voltage VR and the voltage VS at one end of the sense resistor 290 cannot be accurately compared, and the detection accuracy of the chopping current is lowered.

  FIG. 6 shows a layout configuration example of the circuit device 200 of the present embodiment that can solve the above-described problems. The circuit device 200 is mounted on a printed board as an IC chip, for example, and the sense resistor 290 is mounted on the printed board as a circuit component. FIG. 6 is a layout configuration example inside the circuit device 200 when the printed circuit board is viewed in plan.

  As shown in FIG. 6, the upper direction in the drawing is the first direction DR1, the opposite direction of the first direction DR1 is the second direction DR2, and the direction orthogonal to the first direction DR1 is the third direction DR3. The direction opposite to the third direction DR3 is defined as a fourth direction DR4.

  It is assumed that the first side HN1 of the circuit device 200 is disposed on the fourth direction DR4 side, and the second side HN2 is disposed on the second direction DR2 side. In this case, the first bridge circuit region, the second bridge circuit region, the driver circuit region, the analog circuit region, and the logic circuit region are arranged in this order in the first direction DR1 from the second side HN2 side. The second bridge circuit region is arranged on the third direction DR3 side of the first bridge circuit region.

  The bridge circuit 210 of FIG. 3 is disposed in each of the first bridge circuit region and the second bridge circuit region. A pre-driver 260 is disposed in the driver circuit area, a detection circuit 250 is disposed in the analog circuit area, and a control circuit 240 is disposed in the logic circuit area.

  The I / O area is an area for inputting / outputting signals and voltages to / from the outside. The I / O area includes, for example, a pad area and an electrostatic protection circuit. The I / O region is arranged along the third side HN3 on the first direction DR1 side of the logic circuit region. Further, the logic circuit area, the analog circuit area, and the driver circuit area are arranged along the first side HN1 on the fourth direction DR4 side.

  In the above layout, the distance between the third terminal RNF and the bridge circuit 210 (first bridge circuit region) is based on the distance between the first terminal SN1 and the bridge circuit 210 and the distance between the second terminal SN2 and the bridge circuit 210. Also short.

  For example, the distance between the terminal and the bridge circuit 210 is defined by the distance from the terminal to the center point of the arrangement area of the bridge circuit 210. In this case, the first terminal SN1 and the second terminal SN2 are provided at positions farther from the center point of the first bridge circuit region than the third terminal RNF.

  In the above layout, the distance between the first terminal SN1 and the detection circuit 250 (analog circuit region) and the distance between the second terminal SN2 and the detection circuit 250 are larger than the distance between the third terminal RNF and the detection circuit 250. short.

  For example, the distance between the terminal and the detection circuit 250 is defined by the distance from the terminal to the center point of the arrangement area of the detection circuit 250. In this case, the first terminal SN1 and the second terminal SN2 are provided closer to the center point of the analog circuit area than the third terminal RNF. Alternatively, the distance between the terminal and the detection circuit 250 may be defined by the distance from the terminal to the center point of the arrangement region of the differential amplifier circuit 270.

  As described above, the parasitic diode Dp1 that causes the substrate potential to fluctuate is generated in the bridge circuit 210. In the present embodiment, the bridge circuit 210 is arranged away from the first terminal SN1 and the second terminal SN2, and the detection circuit 250 is arranged near the first terminal SN1 and the second terminal SN2, so that the bridge The circuit 210 and the detection circuit 250 can be separated. This makes it difficult for the fluctuation of the substrate potential generated in the bridge circuit 210 to be transmitted to the detection circuit 250, and the detection error of the chopping current can be reduced.

  In such a layout, since the sense resistor 290 is considered to be provided near the third terminal RNF, the wiring from both ends of the sense resistor 290 to the first terminal SN1 and the second terminal SN2 becomes long. is expected. However, since the input impedance of the differential amplifier circuit 270 is higher than the parasitic resistance, almost no current flows through the wiring from the both ends of the sense resistor 290 to the first terminal SN1 and the second terminal SN2, and due to the parasitic resistance. Little voltage drop occurs. Therefore, even if the first terminal SN1 and the second terminal SN2 are arranged away from the bridge circuit 210, the detection accuracy of the chopping current is not affected.

  In the above layout, the circuit device 200 includes the ground terminal AGND connected to the substrate of the circuit device 200. The distance between the ground terminal AGND and the first terminal SN1 and the distance between the ground terminal AGND and the second terminal SN2 are shorter than the distance between the ground terminal AGND and the third terminal RNF.

  Considering the positional relationship between the terminal and the bridge circuit 210 described above, the distance between the ground terminal AGND and the bridge circuit 210 (first bridge circuit region) is longer than the distance between the third terminal RNF and the bridge circuit 210. That is, the ground terminal AGND is disposed at a position away from the bridge circuit 210.

  The current that flows from the parasitic diode Dp1 of the bridge circuit 210 to the ground flows to the ground terminal AGND through the substrate. Since the ground terminal AGND is arranged away from the bridge circuit 210, the current path from the parasitic diode Dp1 to the ground terminal AGND becomes long, and the substrate resistance of the path can be increased. It is considered that the higher the substrate resistance, the more difficult the current flows from the parasitic diode Dp1 to the substrate. Therefore, the fluctuation of the substrate potential can be reduced, and the detection circuit 250 can accurately measure the chopping current.

  In the above layout, the circuit device 200 includes a pre-driver 260 that drives the bridge circuit 210 based on an on / off control signal from the control circuit 240. The first terminal SN1 and the second terminal SN2 are disposed on the first side HN1 of the circuit device 200, and the third terminal RNF is disposed on the second side HN2 of the circuit device 200. The first direction DR1 is a direction from the second side HN2 to the third side HN3 facing the second side HN2. In this case, the pre-driver 260 (driver circuit area) is arranged on the first direction DR1 side of the bridge circuit 210 (first bridge circuit area), and the detection circuit 250 (analog circuit area) is connected to the pre-driver 260. It arrange | positions at the 1st direction DR1 side.

  In this way, the bridge circuit 210 is arranged on the second side HN2 side where the third terminal RNF is arranged, and the pre-driver 260 and the detection circuit 250 are arranged in the first direction DR1 along the first side HN1. Can be placed. Then, the first terminal SN1 and the second terminal SN2 can be connected to the detection circuit 250 from the first side HN1 side. With such an arrangement, the bridge circuit 210 and the detection circuit 250 are naturally arranged apart from each other. As a result, the influence of the substrate potential fluctuation can be suppressed as described above.

5. Measurement result of detection error of chopping current FIGS. 7 and 8 show the results of measurement of detection error of chopping current.

  FIG. 7 is a waveform obtained by measuring the voltage at one end of the sense resistor 290 in the comparative example (VS in FIG. 1) and the voltage difference between both ends of the sense resistor in the present embodiment (VI1-VI2 in FIG. 3). The peak value (maximum value) indicated by A1 is a voltage when it is detected that the reference voltage has been reached in each charge period. This voltage corresponds to the chopping current IL described in FIG.

  FIG. 8 shows the deviation of the chopping current measured at each set value (code) of the D / A conversion circuit 230. That is, the waveform of FIG. 7 is acquired with each set value, the voltage peak value in each charge period is converted into a chopping current, and the measured chopping current is statistically processed to obtain a deviation. The measurement values indicated by circles are the measurement values in the comparative example described in FIG. The measurement values indicated by the square marks are the measurement values in the present embodiment described with reference to FIGS.

  In the comparative example, since the detected value of the chopping current varies due to the above-described parasitic resistance and substrate potential fluctuation, the deviation is large. On the other hand, in this embodiment, since the influence of variations in parasitic resistance and substrate potential can be suppressed, the deviation is smaller than in the comparative example. Further, when the set value of the D / A conversion circuit 230 (that is, the set value of the chopping current) is changed, the variation of the deviation is smaller than that of the comparative example.

  As described above, in this embodiment, since the variation in detection of the chopping current is reduced, the chopping current can be accurately detected even if the sense resistor 290 is reduced. As a result, the sense resistor 290 can be reduced to improve the power efficiency of the motor drive.

6). Electronic Device FIG. 9 shows a configuration example of an electronic device to which the circuit device 200 of the present embodiment is applied. The electronic device includes a processing unit 300, a storage unit 310, an operation unit 320, an input / output unit 330, a circuit device 200, a bus 340 connecting these units, and a motor 280. The circuit device 200 can be realized by an integrated circuit device, for example.

  In the following description, a printer that controls the head and paper feeding by motor drive will be described as an example. However, the present embodiment is not limited to this and can be applied to various electronic devices.

  The input / output unit 330 is configured by an interface such as a USB connector or a wireless LAN, and receives image data and document data. The input data is stored in the storage unit 310 which is an internal storage device such as a DRAM. When the printing instruction is received by the operation unit 320, the processing unit 300 starts a printing operation of data stored in the storage unit 310. The processing unit 300 sends an instruction to the circuit device 200 in accordance with the print layout of the data, and the circuit device 200 rotates the motor 280 based on the instruction to move the head and feed the paper.

  Although the present embodiment has been described in detail as described above, it will be easily understood by those skilled in the art that many modifications can be made without departing from the novel matters and effects of the present invention. Accordingly, all such modifications are intended to be included in the scope of the present invention. For example, a term described at least once together with a different term having a broader meaning or the same meaning in the specification or the drawings can be replaced with the different term in any part of the specification or the drawings. All combinations of the present embodiment and the modified examples are also included in the scope of the present invention. Further, the configurations and operations of the detection circuit, the control circuit, the bridge circuit, the pre-driver, the circuit device, and the electronic device are not limited to those described in this embodiment, and various modifications can be made.

200 circuit device, 210 bridge circuit, 221 comparator,
230 D / A conversion circuit, 240 control circuit, 250 detection circuit,
260 pre-drivers, 261 to 264 buffers, 270 differential amplifier circuits,
271 operational amplifier, 272 to 275 resistance element, 280 motor,
290 sense resistor, 300 processing unit, 310 storage unit, 320 operation unit,
330 I / O unit, 340 bus,
AGND ground terminal, DR1 to DR4, first to fourth directions,
Dp1 parasitic diode, HN1 to HN3, first to third sides,
IL chopping current, Id current, L1 to L4, first to fourth wirings,
NI1, NI2 first and second input nodes, Q1-Q4 transistors,
RNF third terminal, Rp1, Rp2 parasitic resistance, Rsub substrate resistance,
SN1, SN2 first and second terminals, TC charge period,
TD decay period, VR reference voltage

Claims (10)

A bridge circuit having a high-side transistor and a low-side transistor;
A first terminal for connecting to one end of a sense resistor for detecting a current flowing in the bridge circuit;
A second terminal for connection to the other end of the sense resistor;
A third terminal connected to the source side of the low-side transistor;
A circuit device comprising: In claim 1,
A charge current in a charge period is detected by detecting a voltage difference between a first voltage that is the voltage at the one end of the sense resistor and a second voltage that is the voltage at the other end of the sense resistor. A detection circuit;
A control circuit that performs on / off control of the high-side transistor and the low-side transistor based on the detection result of the detection circuit;
Including
The first terminal is connected to a first input node of the detection circuit;
The second terminal is connected to a second input node of the detection circuit;
The circuit device according to claim 3, wherein the third terminal is a terminal for connecting to the one end of the sense resistor via a wiring. In claim 1 or 2,
The distance between the third terminal and the bridge circuit is shorter than the distance between the first terminal and the bridge circuit and the distance between the second terminal and the bridge circuit. In claim 2,
The circuit device characterized in that a distance between the first terminal and the detection circuit and a distance between the second terminal and the detection circuit are shorter than a distance between the third terminal and the detection circuit. In any one of Claims 1 thru | or 4,
The first terminal and the second terminal are disposed on a first side of the circuit device;
The circuit device, wherein the third terminal is disposed on a second side of the circuit device. In any one of Claims 1 thru | or 5,
Including a ground terminal connected to a substrate of the circuit device;
The distance between the ground terminal and the first terminal and the distance between the ground terminal and the second terminal are shorter than the distance between the ground terminal and the third terminal. In claim 2,
Including a pre-driver for driving the bridge circuit based on the on / off control signal;
The first terminal and the second terminal are disposed on a first side of the circuit device;
The third terminal is disposed on a second side of the circuit device;
When the first direction is the direction from the second side to the third side opposite to the second side, the pre-driver is disposed on the first direction side of the bridge circuit, The circuit device, wherein the detection circuit is arranged on the first direction side of the pre-driver. In claim 2,
The detection circuit includes a differential amplifier circuit that differentially amplifies the first voltage input to the first input node and the second voltage input to the second input node. A circuit device characterized. A circuit board on which the circuit device according to any one of claims 1 to 8 is mounted,
A first wiring connecting the first terminal and the one end of the sense resistor;
A second wiring connecting the second terminal and the other end of the sense resistor;
A third wiring connecting the third terminal and the one end of the sense resistor;
A circuit board comprising:   An electronic apparatus comprising the circuit device according to claim 1.

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