Drive circuit

Abstract

The present invention improves signal quality in a drive circuit having a driver.　This drive circuit comprises a driver, an amplitude adjusting unit, and a common voltage adjusting unit. In the drive circuit, the driver outputs a differential signal. The amplitude adjusting unit generates, from one of a pair of voltages, the other of the pair of voltages, and supplies the other voltage to one of a power supply terminal and a ground terminal of the driver. The common voltage adjusting unit generates, from an intermediate voltage of the pair of voltages, one of the pair of voltages, and supplies the one voltage to the other of the power supply terminal and the ground terminal.

Description

Technical Field

[0001] The present technology relates to a drive circuit. More specifically, it relates to a drive circuit that outputs a signal.

Background Art

[0002] Conventionally, in a drive circuit on the transmission side of a communication interface, in addition to a driver, a voltage regulator is often arranged to control the amplitude of the driver. For example, a drive circuit has been proposed in which voltage regulators are provided on each of the power supply side and the ground side together with a driver (see, for example, Patent Document 1). The voltage regulator on the power supply side in this drive circuit generates the high level of the driver output from a predetermined reference voltage, and the voltage regulator on the ground side generates the low level of the driver output from that reference voltage.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above - mentioned conventional technology, by arranging voltage regulators on both the power supply side and the ground side, an improvement in PSRR (Power Supply Rejection Ratio) is attempted. However, in the above - mentioned drive circuit, due to the input offset of the operational amplifier in the voltage regulator, variations may occur in the amplitude and common voltage of the output signal of the driver. These variations may cause a deterioration in signal quality.

[0005] The present technology has been created in view of such a situation, and an object thereof is to improve signal quality in a drive circuit provided with a driver.

Means for Solving the Problems

[0006] This technology has been made to solve the above-mentioned problems. Its first aspect is a drive circuit comprising a driver that outputs a differential signal, an amplitude adjustment unit that generates one of the pair of voltages from the other of the pair of voltages and supplies it to one of the power supply terminal and the ground terminal of the driver, and a common voltage adjustment unit that generates one of the pair of voltages from the intermediate voltage between the pair of voltages and supplies it to the other of the power supply terminal and the ground terminal. This brings about the effect that the amplitude and the common voltage are adjusted.

[0007] Also, in this first aspect, the common voltage adjustment unit may include a common-side reference voltage generation unit that generates a predetermined common-side reference voltage, and an operational amplifier that generates one of the pair of voltages from the common-side reference voltage and the intermediate voltage. This brings about the effect that one of the pair of voltages is generated from the common-side reference voltage and the intermediate voltage.

[0008] Also, in this first aspect, the common-side reference voltage generation unit may include a pair of first resistors connected in series between a power supply node and a ground node, and the voltage of the connection node of the pair of first resistors may be supplied as the common-side reference voltage. This brings about the effect that the power supply voltage is divided.

[0009] Also, in this first aspect, the common-side reference voltage generation unit may include a pair of first transistors connected in series between a power supply node and a ground node, and the voltage of the connection node of the pair of first transistors may be supplied as the common-side reference voltage. This brings about the effect that the power supply voltage is divided.

[0010] Also, in this first aspect, the common-side reference voltage generation unit may include a pair of first capacitors connected in series between a power supply node and a ground node, and the voltage of the connection node of the pair of first capacitors may be supplied as the common-side reference voltage. This brings about the effect that the difference in the power supply voltage is divided.

[0011] Also, in this first aspect, an intermediate voltage generation unit that generates the intermediate voltage from the pair of voltages may be further provided. This brings about the effect that the intermediate voltage is generated from the pair of voltages.

[0012] Also, in this first aspect, the intermediate voltage generation unit may include a pair of second resistors connected in series between the pair of voltages, and the voltage of the connection node of the pair of second resistors may be supplied as the intermediate voltage. This brings about the effect that the difference between the pair of voltages is divided.

[0013] Also, in this first aspect, the intermediate voltage generation unit may include a pair of second transistors connected in series between the pair of voltages, and the voltage of the connection node of the pair of second transistors may be supplied as the intermediate voltage. This brings about the effect that the difference between the pair of voltages is divided.

[0014] Also, in this first aspect, the intermediate voltage generation unit may include a pair of second capacitors connected in series between the pair of voltages, and the voltage of the connection node of the pair of second capacitors may be supplied as the intermediate voltage. This brings about the effect that the difference between the pair of voltages is divided.

[0015] Also, in this first aspect, the amplitude adjustment unit may include an amplitude-side reference voltage generation unit that generates a predetermined amplitude-side reference voltage, and a negative feedback circuit that generates the other of the pair of voltages from the amplitude-side reference voltage and one of the pair of voltages. This brings about the effect that the other of the pair of voltages is negatively feedbacked.

[0016] Also, in this first aspect, the amplitude-side reference voltage generation unit may include a current source and a third resistor connected in series between one of the pair of voltages and one of the power supply node and the ground node, and the voltage of the connection node of the current source and the third resistor may be supplied as the amplitude-side reference voltage. This brings about an effect of generating a voltage corresponding to the current of the current source and the resistance value of the third resistor.

[0017] Also, in this first aspect, the amplitude adjustment unit may generate the higher one of the pair of voltages from the lower one of the pair of voltages and supply it to the power supply terminal, and the common voltage adjustment unit may generate the lower one of the pair of voltages from the intermediate voltage and supply it to the ground terminal. This brings about an effect that the amplitude adjustment unit is arranged on the power supply side and the common voltage adjustment unit is arranged on the ground side.

[0018] Also, in this first aspect, the amplitude adjustment unit may generate the lower one of the pair of voltages from the higher one of the pair of voltages and supply it to the ground terminal, and the common voltage adjustment unit may generate the higher one of the pair of voltages from the intermediate voltage and supply it to the power supply terminal. This brings about an effect that the amplitude adjustment unit is arranged on the ground side and the common voltage adjustment unit is arranged on the power supply side.

[0019] Also, in this first aspect, the driver may be an SST (Source Series Terminated) type driver. This brings about an effect that the voltage required for driving the driver is reduced and the speed is increased.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

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Figure 8

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Figure 10

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Figure 14

Embodiments for Carrying Out the Invention

[0021] Hereinafter, embodiments for carrying out the present technology (hereinafter referred to as embodiments) will be described. The description will be made in the following order. 1. First Embodiment (Example in which an amplitude adjustment unit is arranged on the power supply side and a common voltage adjustment unit is arranged on the ground side) 2. Second Embodiment (Example where the amplitude adjustment unit is arranged on the ground side and the common voltage adjustment unit is arranged on the power supply side) 3. Application Examples to Moving Bodies

[0022] <1. First Embodiment> [Configuration Example of Interface Circuit] FIG. 1 is a block diagram showing a configuration example of an interface circuit in an embodiment of the present technology. This interface circuit is a circuit for transmitting signals and includes a transmission circuit 100 and a reception circuit 300. In this interface circuit, for example, the LVDS (Low Voltage Differential Signaling) standard is used.

[0023] The transmission circuit 100 is a circuit for transmitting signals and includes a transmission signal generation unit 110 and a drive circuit 200.

[0024] The transmission signal generation unit 110 generates a signal to be transmitted. This transmission signal generation unit 110 generates, for example, a differential signal and supplies it to the drive circuit 200 via the signal line 119.

[0025] The drive circuit 200 amplifies the differential signal from the transmission signal generation unit 110 and outputs it to the transmission line 209. The reception circuit 300 receives the differential signal from the drive circuit 200 by a receiver or the like.

[0026] [Configuration Example of Drive Circuit] FIG. 2 is a block diagram showing a configuration example of the drive circuit 200 in the first embodiment of the present technology. This drive circuit 200 includes an amplitude adjustment unit 210, a common voltage adjustment unit 230, and an output unit 250.

[0027] The output unit 250 generates a differential signal based on the input signal VIN which is a differential signal, and supplies it as the output signal VOUT to the receiving circuit 300 via the transmission line 209. Also, a high voltage VRH is input to the power supply terminal of the output unit 250, and a low voltage VRL is input to the ground terminal of the output unit 250. Here, the low voltage VRL is lower than the high voltage VRH. Further, the output unit 250 generates an intermediate voltage VC between the high voltage VRH and the low voltage VRL, and supplies it to the common voltage adjustment unit 230. Note that the high voltage VRH and the low voltage VRL are examples of a pair of voltages described in the claims.

[0028] The amplitude adjustment unit 210 adjusts the amplitude of the output signal VOUT (i.e., the differential signal). This amplitude adjustment unit 210 generates the high voltage VRH from the low voltage VRL, and supplies it to the power supply terminal of the output unit 250.

[0029] The common voltage adjustment unit 230 adjusts the common voltage of the differential signal. This common voltage adjustment unit 230 generates the low voltage VRL from the intermediate voltage VC, and supplies it to the ground terminal of the output unit 250.

[0030] FIG. 3 is a circuit diagram showing a configuration example of the amplitude adjustment unit 210, the common voltage adjustment unit 230, and the output unit 250 in the first embodiment of the present technology. The amplitude adjustment unit 210 includes an amplitude-side reference voltage generation unit 220 and a negative feedback circuit 215. The negative feedback circuit 215 includes a resistor 211, a variable resistor 212, an operational amplifier 213, and a pMOS (p-channel Metal Oxide Semiconductor) transistor 214.

[0031] The amplitude adjustment unit 210 generates a predetermined amplitude-side reference voltage V swref from the low voltage VRL.

[0032] The resistor 211 and the variable resistor 212 are connected in series between the node of the high voltage VRH and the node of the low voltage VRL.

[0033] The amplitude-side reference voltage V is applied to the inverting input terminal (-) of the operational amplifier 213.swref is input, and the non-inverting input terminal (+) is connected to the connection node of resistor 211 and variable resistor 212. Also, the output terminal of operational amplifier 213 is connected to the gate of pMOS transistor 214.

[0034] The source of pMOS transistor 214 is connected to the node of power supply voltage Vdd, and the drain is connected to variable resistor 212. The voltage at the connection node of pMOS transistor 214 and variable resistor 212 is supplied to output section 250 as high voltage VRH.

[0035] Also, common voltage adjustment section 230 includes common-side reference voltage generation section 240, operational amplifier 231, and nMOS (n-channel MOS) transistor 232.

[0036] Common-side reference voltage generation section 240 generates a predetermined common-side reference voltage V coref .

[0037] The intermediate voltage VC is input to the non-inverting input terminal (+) of operational amplifier 231, and the common-side reference voltage V coref is input to the inverting input terminal (-). Also, the output terminal of operational amplifier 231 is connected to the gate of nMOS transistor 232.

[0038] The source of nMOS transistor 232 is connected to the ground node of ground voltage. Also, the voltage at the drain of nMOS transistor 232 is supplied to amplitude adjustment section 210 and output section 250 as low voltage VRL.

[0039] Also, output section 250 includes intermediate voltage generation section 260 and driver 270. The high voltage VRH from amplitude adjustment section 210 is supplied to the power supply terminal of driver 270 via intermediate voltage generation section 260. Also, the low voltage VRL from common voltage adjustment section 230 is supplied to the ground terminal of driver 270 via intermediate voltage generation section 260.

[0040] The intermediate voltage generation unit 260 generates an intermediate voltage VC from the high voltage VRH and the low voltage VRL. The driver 270 generates and outputs a differential output signal based on the differential input signal.

[0041] FIG. 4 is a circuit diagram showing a configuration example of the amplitude-side reference voltage generation unit 220, the common-side reference voltage generation unit 240, and the intermediate voltage generation unit 260 in the first embodiment of the present technology.

[0042] The amplitude-side reference voltage generation unit 220 includes, for example, a current source 221 and a resistor 222. These current source 221 and resistor 222 are connected in series between the power supply node of the power supply voltage Vdd and the node of the low voltage VRL, with the current source 221 on the power supply side. Also, the voltage of the connection node of the current source 221 and the resistor 222 is supplied to the operational amplifier 213 as the amplitude-side reference voltage V swref Note that the resistor 222 is an example of the third resistor described in the claims.

[0043] Also, the common-side reference voltage generation unit 240 includes, for example, resistors 241 and 242 and a capacitor 243. The resistors 241 and 242 are connected in series between the power supply node and the ground node. The capacitor 243 is inserted between the connection node of the resistors 241 and 242 and the ground node. The voltage of the connection node of the resistors 241 and 242 is supplied to the operational amplifier 231 as the common-side reference voltage V cоref Note that the resistors 241 and 242 are examples of the first resistor described in the claims.

[0044] Also, the intermediate voltage generation unit 260 includes, for example, resistors 261 and 262 having substantially the same resistance value. These resistors are connected in series between the high voltage VRH and the low voltage VRL. Also, the voltage of the connection node of the resistors 261 and 262 is supplied to the operational amplifier 231 as the intermediate voltage VC. Note that the resistors 261 and 262 are examples of the second resistor described in the claims.

[0045] With the circuit configuration illustrated in the figure, in the amplitude adjustment unit 210, the high voltage VRH is negatively fed back to the non-inverting input terminal (+) of the operational amplifier 213, and the amplitude is adjusted by this negative feedback circuit. Also, in the common voltage adjustment unit 230, the low voltage VRL is negatively fed back to the non-inverting input terminal (+) of the operational amplifier 231, and the common voltage is adjusted by this negative feedback circuit. The thick lines in the figure indicate the paths of negative feedback.

[0046] Assuming the value of the current supplied by the current source 221 is I' and the resistance value of the resistor 222 is R', the amplitude-side reference voltage V swref is expressed by the following equation. V swref = VRL + I'R' ··· Equation 1

[0047] Also, due to the negative feedback on the amplitude adjustment unit 210 side, assuming the resistance value of the resistor 211 is R1 and the resistance value of the variable resistor 212 is R2, the voltage V + at the non-inverting input terminal (+) of the operational amplifier 213 is expressed by the following equation. V + = (R1·VRH + R2·VRL) / (R1 + R2) ··· Equation 2

[0048] Also, the input offset ofs2 of the operational amplifier 213 is expressed by the following equation. ofs2 = V + - V swref ··· Equation 3

[0049] Substituting Equation 1 and Equation 2 into Equation 3 and transforming, the following equation is obtained. VRH = {(R1 + R2) / R1}(I'R' + ofs2) + VRL … Equation 4

[0050] Also, from Equation 4, the difference (i.e., the amplitude) ΔV between the high voltage VRH and the low voltage VRL is expressed by the following equation. ΔV = {(R1 + R2) / R1}(I'R' + ofs2) ··· Equation 5

[0051] Based on Equation 5, the offset component of the amplitude ΔV is expressed by the following equation. {(R1 + R2) / R1} of s2 ··· Equation 6

[0052] Also, when the resistance values of resistors 241 and 242 are made substantially the same, the common-side reference voltage V cоref is represented by the following equation. V cоref = Vdd / 2 ··· Equation 7

[0053] Also, the input offset ofs1 of the operational amplifier 231 is represented by the following equation. ofs1 = VC - V cоref ··· Equation 8

[0054] Substituting Equation 7 into Equation 8 gives the following equation. VC = Vdd / 2 + ofs1 ··· Equation 9

[0055] Also, due to the negative feedback on the common voltage adjustment unit 230 side, the intermediate voltage VC is represented by the following equation. VC = VRL + ΔV / 2 ··· Equation 10

[0056] Substituting and transforming Equations 5 and 9 into Equation 10 gives the following equation. VRL = Vdd / 2 + ofs1 -{(R1 + R2) / 2R1}(I'R' + ofs2)… Equation 11

[0057] Substituting Equation 11 into Equation 4 gives the following equation. VRH = Vdd / 2 + ofs1 +{(R1 + R2) / 2R1}(I'R' + ofs2)… Equation 12

[0058] From Equations 11 and 12, the offset component of the common voltage is ofs1.

[0059] [Configuration Example of Driver] FIG. 5 is a circuit diagram showing a configuration example of the driver 270 in the first embodiment of the present technology. This driver 270 includes pMOS transistors 271, 273, 276, and 279, and nMOS transistors 272, 274, 277, and 280. Further, the driver 270 includes regulators 275 and 278, and resistors 281 and 282.

[0060] The pMOS transistor 271 and the nMOS transistor 272 are connected in series between the power supply node and the ground node and function as the first-stage inverter. The pMOS transistor 273 and the nMOS transistor 274 are connected in series between the power supply node and the ground node and function as the second-stage inverter.

[0061] The regulator 275 controls the voltage at the sources of the pMOS transistors 276 and 279 to be constant. The regulator 278 controls the voltage at the sources of the nMOS transistors 277 and 280 to be constant.

[0062] The pMOS transistor 276 and the nMOS transistor 277 are connected in series between the regulators 275 and 278 and function as the third-stage inverter. The pMOS transistor 279 and the nMOS transistor 280 are connected in series between the regulators 275 and 278 and function as the fourth-stage inverter.

[0063] The negative input signal VIN- is input to the first-stage inverter, and the output of that inverter is input to the fourth-stage inverter. The positive input signal VIN+ is input to the second-stage inverter, and the output of that inverter is input to the third-stage inverter.

[0064] The output of the third-stage inverter is connected to one end of the resistor 281, and the positive output signal VOUT+ is output from the other end of that resistor 281. The output of the fourth-stage inverter is connected to one end of the resistor 282, and the negative output signal VOUT- is output from the other end of that resistor 282.

[0065] As illustrated in the figure, a driver 270 having a circuit configuration in which termination resistors (i.e., resistor 281 and resistor 282) are inserted in series with the output of a subsequent-stage circuit (the third-stage and fourth-stage inverters) is called an SST (Source Series Terminated) type driver. Since this SST type can be driven at a low voltage and is fast compared with the nMOS type described later, drivers for performing serial data communication are shifting from the NMOS type to the SST type. However, the SST type driver has a problem in that the variation in the offset component of the common voltage is large. In particular, the deterioration of the error is remarkable at high amplitudes with a large gain setting. For this reason, especially when using an SST type driver, it is required to adjust the common voltage and reduce its variation.

[0066] Here, assume a drive circuit having a configuration in which the amplitude adjustment unit 210 and the common voltage adjustment unit 230 are not arranged as a comparative example.

[0067] FIG. 6 is a circuit diagram showing a configuration example of a drive circuit 200 in the comparative example. The drive circuit 200 of this comparative example includes a high-voltage side voltage regulator 219, a low-voltage side voltage regulator 410, a reference voltage generation circuit 430, and a driver 270. The high-voltage side voltage regulator 219 includes a current source 221, a resistor 222, a resistor 211, a variable resistor 212, an operational amplifier 213, and a pMOS transistor 214. The connection configuration of these elements is the same as that of the amplitude adjustment unit 210. However, the connection node of the resistor 222 and the resistor 211 is not connected to the node of the low voltage VRL, and the reference voltage V ref is input. V ref = Vdd / 2 + ofs ··· Equation 13

[0068] In the above equation, ofs is the input offset of the operational amplifier in the reference voltage generation circuit 430.

[0069] Substitute VRL in Equation 4 with V in Equation 13 refBy replacing it, the following equation is obtained. VRH = {(R1 + R2) / R1}(I'R' + оfs2) + Vdd / 2 + оfs ··· Equation 14

[0070] Also, the low-voltage side voltage regulator 410 includes a current source 421, a resistor 422, a resistor 411, a variable resistor 412, an operational amplifier 413, and an nMOS transistor 414. The connection configuration of these elements is vertically symmetric with the high-voltage side voltage regulator 219. That is, the resistor 422 is inserted on the power supply side. Also, the connection node of the current source 421 and the resistor 422 is connected to the inverting input terminal (-) of the operational amplifier 413, and the connection node of the resistor 411 and the variable resistor 412 is connected to the non-inverting input terminal (+) of the operational amplifier 413. Also, the low-voltage side voltage regulator 410 supplies the low voltage VRL to the driver 270.

[0071] The current values and resistance values of the current source 421, the resistor 422, the resistor 411, and the variable resistor 412 are the same as those of the current source 221, the resistor 222, the resistor 211, and the variable resistor 212, and the input offset of the operational amplifier 413 is set to оfs1. In this case, the following equation is obtained. VRL = {(R1 + R2) / R1}(-I'R' + оfs1) + Vdd / 2 + оfs ··· Equation 15

[0072] Based on Equation 14 and Equation 15, the offset component of the amplitude is represented by the following equation. {(R1 + R2) / R1}оfs2 -{(R1 + R2) / R1}оfs1 ··· Equation 16

[0073] Also, the offset component of the common voltage is represented by the following equation. {(R1 + R2) / 2R1}оfs2 + {(R1 + R2) / 2R1}оfs1 + оfs ··· Equation 17

[0074] From Equation 6 and Equation 16, by providing the amplitude adjustment unit 210 that refers to the low voltage VRL, the influence of the input offset ofs1 on the ground side can be canceled from the offset component of the amplitude. In contrast, in a comparative example that does not refer to the low voltage VRL, the influence of the input offset ofs1 cannot be canceled. Therefore, the latter has a larger variation in amplitude due to the offset.

[0075] Also, from Equation 17, by providing the common voltage adjustment unit 230 that refers to the intermediate voltage, the influence of the input offsets ofs and ofs2 can be canceled from the offset component of the common voltage. In contrast, in a comparative example that does not refer to the intermediate voltage, the influence of the input offsets ofs and ofs2 cannot be canceled. Therefore, the latter has a larger variation in the common voltage due to the offset. In particular, when an SST type driver is used, the variation in the common voltage becomes a problem.

[0076] Although the resistors 241 and 242 are arranged in the common side reference voltage generation unit 240, the circuit configuration is not limited to this.

[0077] For example, as illustrated in a of FIG. 7, a pMOS transistor 244 and an nMOS transistor 245 connected in series between the power supply node and the ground node can also be arranged. These transistors are diode-connected, and their on-resistances are substantially the same. Also, the voltage of the connection node of the pMOS transistor 244 and the nMOS transistor 245 is supplied as the common side reference voltage V cоref to be supplied.

[0078] Also, as illustrated in b of the same figure, the pMOS transistor 244 in a of the same figure can be replaced with an nMOS transistor 246.

[0079] Also, as illustrated by c in the same figure, the nMOS transistor 245 at a in the same figure can be replaced with a pMOS transistor 247. Note that the pMOS transistor 244, nMOS transistor 245, nMOS transistor 246, and pMOS transistor 247 are examples of the first transistor described in the claims.

[0080] Also, as illustrated by d in the same figure, capacitors 248 and 249 connected in series between the power supply node and the ground node can be arranged. The values of these capacitors are substantially the same, and the voltage of the connection node of capacitors 248 and 249 is supplied as the common-side reference voltage V cоref Note that the capacitors 248 and 249 are examples of the first capacitor described in the claims.

[0081] Also, although the resistors 261 and 262 are arranged in the intermediate voltage generation unit 260, the circuit configuration is not limited to this.

[0082] For example, as illustrated by a in FIG. 8, a pMOS transistor 263 and an nMOS transistor 264 connected in series between the node of the high voltage VRH and the node of the low voltage VRL can be arranged. These transistors are diode-connected, and their on-resistances are substantially the same. Also, the voltage of the connection node of the pMOS transistor 263 and the nMOS transistor 264 is supplied as the intermediate voltage VC.

[0083] Also, as illustrated by b in the same figure, the pMOS transistor 263 at a in the same figure can be replaced with an nMOS transistor 265.

[0084] Also, as illustrated by c in the same figure, the nMOS transistor 264 at a in the same figure can be replaced with a pMOS transistor 266. Note that the pMOS transistor 263, nMOS transistor 264, nMOS transistor 265, and pMOS transistor 266 are examples of the second transistor described in the claims.

[0085] Also, as illustrated by d in the same figure, capacitors 267 and 268 connected in series can be arranged between the node of the high voltage VRH and the node of the low voltage VRL. The values of these capacitors are substantially the same, and the voltage of the connection nodes of capacitors 267 and 268 is supplied as the intermediate voltage VC. Note that capacitors 267 and 268 are an example of the second capacitor described in the claims.

[0086] Each of the circuits of the common-side reference voltage generation unit 240 illustrated in FIGS. 4 and 7 and each of the circuits of the intermediate voltage generation unit 260 illustrated in FIGS. 4 and 8 can be arbitrarily combined.

[0087] FIG. 9 is a diagram showing an example of waveforms of differential signals and common voltage components in the first embodiment of the present technology. In the figure, a shows the waveforms of the output signals VOUT+ and VOUT− when there is a shift in the timing of each transition. In the figure, b shows the waveform of the common voltage component corresponding to a in the figure.

[0088] In the figure, c shows the waveforms of the output signals VOUT+ and VOUT− when there is a shift in each rise time. In the figure, d shows the waveform of the common voltage component corresponding to c in the figure.

[0089] In the figure, e shows the waveforms of the output signals VOUT+ and VOUT− when there is a shift in each amplitude. In the figure, f shows the waveform of the common voltage component corresponding to e in the figure.

[0090] In the figure, g shows the waveforms of the output signals VOUT+ and VOUT− with common-mode noise superimposed on each. In the figure, h shows the waveform of the common voltage component corresponding to g in the figure.

[0091] As illustrated in the figure, fluctuations occur in the components of the common voltage due to timing, amplitude, rise-time deviation, and common-mode noise, which cause radiation of external EMI (Electro Magnetic Interference).

[0092] As described above, by arranging the common voltage adjustment unit 230, fluctuations in the common voltage can be suppressed and EMI can be reduced.

[0093] Note that although an SST type driver is used as the driver 270, as illustrated in FIG. 10, an nMOS type driver can also be used. In this case, instead of the third and fourth inverters and the regulator 278, resistors 291 and 292, and nMOS transistors 293 to 296 are arranged.

[0094] In the nMOS type, one end of the resistor 291 is connected to the regulator 275, and the other end is commonly connected to the drains of the nMOS transistors 293 and 295. One end of the resistor 292 is connected to the ground node, and the other end is commonly connected to the sources of the nMOS transistors 294 and 296.

[0095] Also, the nMOS transistors 293 and 294 are connected in series between the resistors 291 and 292. The nMOS transistors 295 and 296 are connected in series between the resistors 291 and 292. The output of the first-stage inverter is input to the gates of the nMOS transistors 294 and 295, and the output of the second-stage inverter is input to the gates of the nMOS transistors 293 and 296. The connection node of the nMOS transistors 293 and 294 is connected to the resistor 282, and the connection node of the nMOS transistors 295 and 296 is connected to the resistor 281.

[0096] Thus, according to the first embodiment of the present technology, since the common voltage adjustment unit 230 generates the low voltage VRL from the intermediate voltage VC and supplies it to the ground terminal of the driver 270, variations in the common voltage can be suppressed. As a result, the quality of the output signal can be improved.

[0097] <2. Second Embodiment> In the above-described first embodiment, the amplitude adjustment unit 210 generates the high voltage VRH, and the common voltage adjustment unit 230 generates the low voltage VRL. However, conversely, the amplitude adjustment unit 210 can generate the low voltage VRL, and the common voltage adjustment unit 230 can generate the high voltage VRH. The drive circuit 200 of this second embodiment is different from the first embodiment in that the amplitude adjustment unit 210 generates the low voltage VRL and the common voltage adjustment unit 230 generates the high voltage VRH.

[0098] FIG. 11 is a block diagram showing a configuration example of the drive circuit 200 in the second embodiment of the present technology. The drive circuit 200 of this second embodiment is different from the first embodiment in that the amplitude adjustment unit 210 generates the low voltage VRL from the high voltage VRH and supplies it to the ground terminal of the driver 270. Also, the common voltage adjustment unit 230 is different from the first embodiment in that it generates the high voltage VRH from the intermediate voltage VC and supplies it to the power supply terminal of the driver 270. Further, an nMOS transistor 215 is arranged in the amplitude adjustment unit 210 instead of a pMOS transistor, and a pMOS transistor 233 is arranged in the common voltage adjustment unit 230 instead of an nMOS transistor.

[0099] As illustrated in the figure, by arranging the amplitude adjustment unit 210 on the ground side, the influence of the input offset of the op-amp on the power supply side can be canceled in terms of amplitude. Also, by arranging the common voltage adjustment unit 230 on the power supply side, the influence of the input offset of the op-amp on the ground side can be canceled in terms of the common voltage.

[0100] FIG. 12 is a circuit diagram showing a configuration example of an amplitude-side reference voltage generation unit 220 in the second embodiment of the present technology. The amplitude-side reference voltage generation unit 220 in the second embodiment is different from the first embodiment in that the current source 221 is arranged on the ground side.

[0101] As described above, according to the second embodiment of the present technology, since the amplitude adjustment unit 210 is arranged on the ground side, the influence of the input offset of the power supply-side operational amplifier can be canceled in terms of amplitude. Also, since the common voltage adjustment unit 230 is arranged on the power supply side, the influence of the input offset of the ground-side operational amplifier can be canceled in terms of the common voltage.

[0102] <3. Application Examples to Moving Bodies> The technology according to the present disclosure (the present technology) can be applied to various products. For example, the technology according to the present disclosure may be realized as a device mounted on any type of moving body such as an automobile, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, a personal mobility device, an airplane, a drone, a ship, a robot, etc.

[0103] FIG. 13 is a block diagram showing a schematic configuration example of a vehicle control system, which is an example of a movement control system to which the technology according to the present disclosure can be applied.

[0104] The vehicle control system 12000 includes a plurality of electronic control units connected via a communication network 12001. In the example shown in FIG. 13, the vehicle control system 12000 includes a drive system control unit 12010, a body system control unit 12020, an out-of-vehicle information detection unit 12030, an in-vehicle information detection unit 12040, and an integrated control unit 12050. Also, as the functional configuration of the integrated control unit 12050, a microcomputer 12051, an audio / video output unit 12052, and an in-vehicle network I / F (interface) 12053 are shown.

[0105] The drive system control unit 12010 controls the operations of devices related to the vehicle's drive system according to various programs. For example, the drive system control unit 12010 functions as a control device for a driving force generation device for generating the driving force of the vehicle such as an internal combustion engine or a driving motor, a driving force transmission mechanism for transmitting the driving force to the wheels, a steering mechanism for adjusting the steering angle of the vehicle, and a braking device for generating the braking force of the vehicle.

[0106] The body system control unit 12020 controls the operations of various devices installed in the vehicle body according to various programs. For example, the body system control unit 12020 functions as a control device for a keyless entry system, a smart key system, a power window device, or various lamps such as a headlamp, a backlamp, a brake lamp, a turn signal, or a fog lamp. In this case, radio waves transmitted from a portable device that substitutes for a key or signals from various switches can be input to the body system control unit 12020. The body system control unit 12020 receives these inputs of radio waves or signals and controls the vehicle's door lock device, power window device, lamps, etc.

[0107] The out-of-vehicle information detection unit 12030 detects information outside the vehicle equipped with the vehicle control system 12000. For example, an imaging unit 12031 is connected to the out-of-vehicle information detection unit 12030. The out-of-vehicle information detection unit 12030 causes the imaging unit 12031 to capture an image outside the vehicle and receives the captured image. The out-of-vehicle information detection unit 12030 may perform object detection processing or distance detection processing such as for a person, a vehicle, an obstacle, a sign, or characters on the road surface based on the received image.

[0108] The imaging unit 12031 is an optical sensor that receives light and outputs an electrical signal according to the amount of received light. The imaging unit 12031 can output the electrical signal as an image or can output it as distance measurement information. Also, the light received by the imaging unit 12031 may be visible light or may be non-visible light such as infrared light.

[0109] The in-vehicle information detection unit 12040 detects information inside the vehicle. For example, a driver state detection unit 12041 that detects the state of the driver is connected to the in-vehicle information detection unit 12040. The driver state detection unit 12041 includes, for example, a camera that images the driver, and the in-vehicle information detection unit 12040 may calculate the degree of driver fatigue or concentration based on the detection information input from the driver state detection unit 12041, or may determine whether the driver is dozing off.

[0110] Based on the information inside and outside the vehicle acquired by the out-vehicle information detection unit 12030 or the in-vehicle information detection unit 12040, the microcomputer 12051 can calculate control target values for the driving force generation device, the steering mechanism, or the braking device, and output a control command to the drive system control unit 12010. For example, the microcomputer 12051 can perform cooperative control for realizing functions of an ADAS (Advanced Driver Assistance System) including collision avoidance or shock mitigation of the vehicle, following driving based on the inter-vehicle distance, vehicle speed maintenance driving, collision warning of the vehicle, or lane departure warning of the vehicle.

[0111] In addition, based on the information around the vehicle acquired by the out-vehicle information detection unit 12030 or the in-vehicle information detection unit 12040, the microcomputer 12051 can perform cooperative control for the purpose of autonomous driving, etc., which controls the driving force generation device, the steering mechanism, or the braking device, etc., to drive autonomously without relying on the driver's operation.

[0112] Also, based on the out-vehicle information acquired by the out-vehicle information detection unit 12030, the microcomputer 12051 can output a control command to the body system control unit 12020. For example, the microcomputer 12051 can perform cooperative control for the purpose of anti-glare, such as controlling the headlamp according to the position of the preceding vehicle or oncoming vehicle detected by the out-vehicle information detection unit 12030 and switching the high beam to the low beam.

[0113] The audio-visual output unit 12052 transmits at least one of an audio output signal and a visual output signal to an output device capable of notifying information visually or aurally to the vehicle occupants or outside the vehicle. In the example of FIG. 13, as the output devices, an audio speaker 12061, a display unit 12062, and an instrument panel 12063 are illustrated. The display unit 12062 may include, for example, at least one of an on-board display and a head-up display.

[0114] FIG. 14 is a diagram showing an example of the installation position of the imaging unit 12031.

[0115] In FIG. 14, the imaging unit 12031 has imaging units 12101, 12102, 12103, 12104, and 12105.

[0116] The imaging units 12101, 12102, 12103, 12104, and 12105 are provided, for example, at positions such as the front nose of the vehicle 12100, side mirrors, rear bumper, back door, and the upper part of the front windshield inside the vehicle cabin. The imaging unit 12101 provided at the front nose and the imaging unit 12105 provided at the upper part of the front windshield inside the vehicle cabin mainly acquire images in front of the vehicle 12100. The imaging units 12102 and 12103 provided at the side mirrors mainly acquire images on the sides of the vehicle 12100. The imaging unit 12104 provided at the rear bumper or the back door mainly acquires images behind the vehicle 12100. The imaging unit 12105 provided at the upper part of the front windshield inside the vehicle cabin is mainly used for detecting a preceding vehicle or pedestrians, obstacles, traffic lights, traffic signs, or lanes.

[0117] Note that FIG. 14 shows an example of the imaging ranges of imaging units 12101 to 12104. Imaging range 12111 indicates the imaging range of imaging unit 12101 provided on the front nose, imaging ranges 12112 and 12113 indicate the imaging ranges of imaging units 12102 and 12103 provided on the side mirrors respectively, and imaging range 12114 indicates the imaging range of imaging unit 12104 provided on the rear bumper or back door. For example, by overlapping the image data captured by imaging units 12101 to 12104, an overhead image of vehicle 12100 viewed from above can be obtained.

[0118] At least one of imaging units 12101 to 12104 may have a function of acquiring distance information. For example, at least one of imaging units 12101 to 12104 may be a stereo camera composed of a plurality of imaging elements, or may be an imaging element having pixels for phase difference detection.

[0119] For example, based on the distance information obtained from imaging units 12101 to 12104, microcomputer 12051 obtains the distance to each solid object within imaging ranges 12111 to 12114 and the temporal change of this distance (relative speed with respect to vehicle 12100), and thus can extract, as the leading vehicle, the closest solid object on the traveling path of vehicle 12100 that travels in substantially the same direction as vehicle 12100 at a predetermined speed (for example, 0 km / h or more). Further, microcomputer 12051 can set the inter-vehicle distance to be secured in advance in front of the leading vehicle, and perform automatic brake control (including follow-up stop control) and automatic acceleration control (including follow-up start control), etc. In this way, cooperative control for the purpose of autonomous driving, etc., which runs autonomously without relying on the driver's operation, can be performed.

[0120] For example, based on the distance information obtained from the imaging units 12101 to 12104, the microcomputer 12051 can classify and extract solid object data related to solid objects into two-wheeled vehicles, ordinary vehicles, large vehicles, pedestrians, utility poles, and other solid objects, and can be used for automatic avoidance of obstacles. For example, the microcomputer 12051 discriminates obstacles around the vehicle 12100 into obstacles visible to the driver of the vehicle 12100 and obstacles difficult to visually recognize. Then, the microcomputer 12051 determines a collision risk indicating the degree of risk of collision with each obstacle, and when the collision risk is equal to or higher than a set value and there is a possibility of collision, it outputs an alarm to the driver via the audio speaker 12061 or the display unit 12062, or performs forced deceleration or avoidance steering via the drive system control unit 12010, thereby providing driving assistance for collision avoidance.

[0121] At least one of the imaging units 12101 to 12104 may be an infrared camera that detects infrared rays. For example, the microcomputer 12051 can recognize a pedestrian by determining whether a pedestrian exists in the captured images of the imaging units 12101 to 12104. Such recognition of a pedestrian is performed, for example, by a procedure of extracting feature points in the captured images of the imaging units 12101 to 12104 as infrared cameras, and a procedure of performing pattern matching processing on a series of feature points indicating the outline of an object to determine whether it is a pedestrian. When the microcomputer 12051 determines that a pedestrian exists in the captured images of the imaging units 12101 to 12104 and recognizes the pedestrian, the audio and image output unit 12052 controls the display unit 12062 to superimpose and display a rectangular outline for emphasis on the recognized pedestrian. Further, the audio and image output unit 12052 may control the display unit 12062 to display an icon or the like indicating a pedestrian at a desired position.

[0122] Above, an example of a vehicle control system to which the technology according to the present disclosure can be applied has been described. The technology according to the present disclosure can be applied to, for example, the imaging unit 12031 among the configurations described above. Specifically, the transmission circuit 100 in FIG. 1 can be applied to the communication interface of the imaging unit 12031. By applying the technology according to the present disclosure to the imaging unit 12031, it is possible to adjust the variations in amplitude and common voltage and improve the signal quality.

[0123] Note that the above-described embodiments show examples for embodying the present technology, and there is a corresponding relationship between the matters in the embodiments and the invention specifying matters in the claims. Similarly, there is a corresponding relationship between the invention specifying matters in the claims and the matters in the embodiments of the present technology with the same name. However, the present technology is not limited to the embodiments, and can be embodied by making various modifications to the embodiments without departing from the gist thereof.

[0124] Note that the effects described in this specification are merely examples and are not limiting, and there may be other effects.

[0125] Note that the present technology can also have the following configuration. (1) A driver that outputs a differential signal, An amplitude adjustment unit that generates the other of the pair of voltages from one of the pair of voltages and supplies it to one of the power supply terminal and the ground terminal of the driver, A common voltage adjustment unit that generates the one of the pair of voltages from the intermediate voltage between the pair of voltages and supplies it to the other of the power supply terminal and the ground terminal A drive circuit comprising (2) The common voltage adjustment unit includes A common side reference voltage generation unit that generates a predetermined common side reference voltage, An operational amplifier that generates the one of the pair of voltages from the common side reference voltage and the intermediate voltage The drive circuit according to (1) above, comprising. (3) The common-side reference voltage generation unit includes a pair of first resistors connected in series between a power supply node and a ground node, and the voltage of the connection node of the pair of first resistors is supplied as the common-side reference voltage The drive circuit according to (2) above. (4) The common-side reference voltage generation unit includes a pair of first transistors connected in series between a power supply node and a ground node, and the voltage of the connection node of the pair of first transistors is supplied as the common-side reference voltage in the drive circuit according to (2) above. (5) The common-side reference voltage generation unit includes a pair of first capacitors connected in series between a power supply node and a ground node, and the voltage of the connection node of the pair of first capacitors is supplied as the common-side reference voltage The drive circuit according to (2) above. (6) The drive circuit further includes an intermediate voltage generation unit that generates the intermediate voltage from the pair of voltages. The drive circuit according to any one of (1) to (5) above. (7) The intermediate voltage generation unit includes a pair of second resistors connected in series between the pair of voltages, and the voltage of the connection node of the pair of second resistors is supplied as the intermediate voltage The drive circuit according to (6) above. (8) The intermediate voltage generation unit includes a pair of second transistors connected in series between the pair of voltages, and the voltage of the connection node of the pair of second transistors is supplied as the intermediate voltage The drive circuit according to (6) above. (9) The intermediate voltage generation unit includes a pair of second capacitors connected in series between the pair of voltages, and the voltage of the connection node of the pair of second capacitors is supplied as the intermediate voltage The drive circuit according to (6) above. (10) The amplitude adjustment unit includes an amplitude-side reference voltage generation unit that generates a predetermined amplitude-side reference voltage, A negative feedback circuit that generates the other voltage of the pair of voltages from the amplitude-side reference voltage and the one of the pair of voltages The drive circuit according to any one of (1) to (9) above, comprising the same. (11) The amplitude-side reference voltage generation unit includes a current source and a third resistor connected in series between the one of the pair of voltages and one of a power supply node and a ground node, The drive circuit according to (10) above, wherein the voltage of the connection node of the current source and the third resistor is supplied as the amplitude-side reference voltage. (12) The amplitude adjustment unit generates the higher voltage of the pair of voltages from the lower voltage of the pair of voltages and supplies it to the power supply terminal, The common voltage adjustment unit generates the lower voltage of the pair of voltages from the intermediate voltage and supplies it to the ground terminal The drive circuit according to any one of (1) to (11) above. (13) The amplitude adjustment unit generates the lower voltage of the pair of voltages from the higher voltage of the pair of voltages and supplies it to the ground terminal, The common voltage adjustment unit generates the higher voltage of the pair of voltages from the intermediate voltage and supplies it to the power supply terminal The drive circuit according to any one of (1) to (11) above. (14) The driver is an SST (Source Series Terminated) type driver The drive circuit according to any one of (1) to (13) above.

Explanation of Signs

[0126] 100 Transmission circuit 110 Transmission signal generation unit 200 Drive circuit 210 Amplitude adjustment unit 211, 222, 241, 242, 261, 262, 281, 282, 291, 292, 411, 422 Resistors 212, 412 Variable resistors 213, 231, 413 Operational amplifiers 214, 233, 244, 247, 263, 266, 271, 273, 276, 279, pMOS transistors 215, 232, 245, 246, 264, 265, 272, 274, 277, 280, 293 - 296, 414 nMOS transistors 215 Negative feedback circuit 219 High - voltage side voltage regulator 220 Amplitude side reference voltage generation unit 221, 421 Current sources 230 Common voltage adjustment unit 240 Common side reference voltage generation unit 243, 248, 249, 267, 268 Capacitors 250 Output unit 260 Intermediate voltage generation unit 270 Driver 275, 278 Regulators 300 Receiver circuit 410 Low - voltage side voltage regulator 430 Reference voltage generation circuit 12031 Imaging unit

Claims

1. A driver that outputs a differential signal, An amplitude adjustment unit that generates the other of the pair of voltages from one of the pair of voltages and supplies it to one of the power supply terminal and the ground terminal of the driver, An intermediate voltage generation unit that generates an intermediate voltage between the pair of voltages from the pair of voltages, A common voltage adjustment unit that generates the one of the pair of voltages from the intermediate voltage and supplies it to the other of the power supply terminal and the ground terminal A drive circuit comprising: The driver outputs the differential signal as an output signal of the drive circuit based on an input signal input to the drive circuit, The amplitude adjustment unit, An amplitude side reference voltage generation unit that generates an amplitude side reference voltage corresponding to one of the pair of voltages, A negative feedback circuit that generates the other of the pair of voltages from the difference between the weighted average of the pair of voltages and the amplitude side reference voltage Comprising, The amplitude adjustment unit adjusts the amplitude of the differential signal by the amplitude side reference voltage generation unit and the negative feedback circuit Drive circuit.

2. The common voltage adjustment unit, A common side reference voltage generation unit that generates a predetermined common side reference voltage, A common side operational amplifier that generates the one of the pair of voltages from the common side reference voltage and the intermediate voltage The drive circuit according to claim 1, comprising:

3. The common side reference voltage generation unit includes a pair of first resistors connected in series between a power supply node and a ground node, The voltage of the connection node of the pair of first resistors is supplied as the common side reference voltage The drive circuit according to claim 2.

4. The common side reference voltage generation unit includes a pair of first transistors connected in series between a power supply node and a ground node, The drive circuit according to claim 2, wherein the voltage of the connection node of the pair of first transistors is supplied as the common side reference voltage.

5. The common side reference voltage generation unit includes a pair of first capacitors connected in series between a power supply node and a ground node, The voltage of the connection node of the pair of first capacitors is supplied as the common side reference voltage The drive circuit according to claim 2.

6. The intermediate voltage generation unit includes a pair of second resistors connected in series between the pair of voltages, The voltage of the connection node of the pair of second resistors is supplied as the intermediate voltage The drive circuit according to claim 1.

7. The intermediate voltage generation unit includes a pair of second transistors connected in series between the pair of voltages, The voltage of the connection node of the pair of second transistors is supplied as the intermediate voltage. The drive circuit according to claim 1.

8. The intermediate voltage generation unit includes a pair of second capacitors connected in series between the pair of voltages, The voltage of the connection node of the pair of second capacitors is supplied as the intermediate voltage. The drive circuit according to claim 1.

9. The negative feedback circuit A pair of third resistors connected in series between the power supply terminal and the ground terminal, An amplitude-side operational amplifier in which the amplitude-side reference voltage is input to the inverting input terminal and the non-inverting input terminal is connected to the connection node of the pair of third resistors, A pMOS (p-channel Metal Oxide Semiconductor) transistor having a gate connected to the output terminal of the amplitude-side operational amplifier and a drain connected to one of the power supply terminal and the ground terminal is provided. The drive circuit according to claim 1.

10. The amplitude-side reference voltage generation unit includes a current source and a fourth resistor connected in series between one of the pair of voltages and one of the power supply node and the ground node, The drive circuit according to claim 1, wherein the voltage of the connection node of the current source and the fourth resistor is supplied as the amplitude-side reference voltage.

11. The amplitude adjustment unit generates the higher one of the pair of voltages from the lower one of the pair of voltages and supplies it to the power supply terminal, The common voltage adjustment unit generates the lower one of the pair of voltages from the intermediate voltage and supplies it to the ground terminal. The drive circuit according to claim 1.

12. The amplitude adjustment unit generates the lower one of the pair of voltages from the higher one of the pair of voltages and supplies it to the ground terminal, The common voltage adjustment unit generates the higher one of the pair of voltages from the intermediate voltage and supplies it to the power supply terminal. The drive circuit according to claim 1.

13. The driver is an SST (Source Series Terminated) type driver. The drive circuit according to claim 1.

Images