A high-precision source measurement unit

Abstract

The present invention discloses a high-precision source measurement unit. On the basis of the prior art, the D / A conversion circuit is improved. A low-noise amplifier Amp and four resistors are used to add the outputs V1 and V2 of two DACs with a set proportionality coefficient of 2 N to increase the resolution of digital-to-analog conversion by N bit, greatly improving the resolution and sampling rate of the D / A conversion circuit, that is, using the DAC splicing technology to achieve high-bandwidth and high-precision signal output. At the same time, in the present invention, both the voltage A / D conversion circuit and the current A / D conversion circuit are time-interleaved analog-to-digital conversion devices, which improves the signal sampling rate and further improves the measurement accuracy and bandwidth.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic measurement, and more specifically, relates to a high-precision source measurement unit. Background Art

[0002] Source Measurement Unit (SMU) is an instrument that integrates the functions of voltage source and current source, used to measure and manipulate the voltage and current of electronic devices. SMU integrates the functions of voltage source and current source, can provide stable voltage and current output at the same time, and can measure the voltage and current on the device, thus simplifying the configuration and connection of the test system. SMU is usually used to test the electrical characteristics and parameters of electronic devices such as semiconductor devices, integrated circuits, sensors, etc.

[0003] A current measurement circuit, a source measurement unit and a semiconductor detection device are disclosed in a Chinese invention patent application with publication number CN 117969940A published on May 3, 2024, which can be applied to the field of semiconductor detection. The current measurement circuit provided by it can automatically switch the resistors involved in the voltage division according to the current size when the current on the power supply line changes at a high rate. The smaller the current of the power supply line, the more resistors participate in the voltage division, and the larger the current of the power supply line, the fewer resistors participate in the voltage division. Based on the optimized configuration of the resistance value of each resistor, the potential difference between the two input terminals of the voltage acquisition module is always in an ideal range, which not only helps to improve the measurement accuracy, but also can avoid the burning of related devices.

[0004] However, the source measurement unit is a closed-loop feedback control system. With the increasing demand for measurement frequency and measurement accuracy, the existing source measurement unit cannot achieve high-precision measurement of broadband electronic devices under test. At the same time, system stability, measurement bandwidth and measurement accuracy have also become key issues restricting the development of SMU instruments. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a high-precision source measurement unit to achieve high-bandwidth and high-precision signal output and high-bandwidth and high-precision measurement of electronic devices.

[0006] To achieve the above-mentioned purpose of the invention, the high-precision source measurement unit of the present invention includes a control unit, a D / A conversion circuit, an output drive circuit, a gear switching circuit, a voltage A / D conversion circuit and a current A / D conversion circuit;

[0007] The control unit controls the D / A conversion circuit to output a precision voltage signal, which is then output to the gear switching circuit for gear switching after the output drive circuit enhances the output drive capability, and then loaded onto the electronic device under test;

[0008] Wherein, the gear switching circuit includes a current gear circuit and a voltage gear circuit;

[0009] The current range circuit is composed of a current sampling resistor array, a current switch matrix and a programmable instrument amplifier, wherein the current sampling resistor array is used for voltage-current conversion and feedback current sampling, the precision voltage signal output by the output drive circuit is loaded onto the electronic device under test through the sampling resistor array, the current switch matrix realizes current output range switching and current measurement range switching by selecting different sampling resistors in the current sampling resistor array to access the path from the output drive circuit to the electronic device under test, and the programmable instrument amplifier obtains the voltage across the sampling resistor and sends it to the current A / D conversion circuit for analog-to-digital conversion to obtain the current measurement value and input it into the control unit;

[0010] The voltage range circuit is composed of a voltage switch matrix and a programmable instrument amplifier. The voltage switch matrix is ​​used to select a local measurement mode or a remote measurement mode to obtain the voltage across the electronic device under test. Then, the programmable instrument amplifier processes the obtained voltage and sends it to the voltage A / D conversion circuit to obtain the voltage measurement value and input it into the control unit.

[0011] The D / A conversion circuit includes two DACs, a low noise amplifier and four resistors R 1 , R 2 , R 3 , R 4 The output voltage of the first DAC is directly input to the positive input terminal of the low noise amplifier, and the output voltage of the second DAC is input through the resistor R 2 Input to the negative input terminal of the low noise amplifier through the resistor R 4 Connect the output terminal of the low noise amplifier to the negative input terminal. The negative input terminal of the low noise amplifier is connected to the negative input terminal through the resistor R 3 to ground through resistor R 1 To the output offset adjustment voltage V CC , get the precise voltage signal V O :

[0012]

[0013] Among them, V 1 The voltage converted from the high-bit voltage value output by the control unit, V 2 The voltage converted from the low-bit voltage value output by the control unit, V CC Output offset adjustment voltage, four resistors R 1 , R 2 , R 3 , R 4 According to the set proportionality factor 2 N To confirm:

[0014] 2 N =1+R 2 / R 1 +R 2 / R 3 +R 2 / R 4

[0015] Wherein, N is the digital-to-analog conversion resolution that needs to be improved, which is a positive integer, and its value is less than or equal to the resolution of the second DAC;

[0016] The voltage A / D conversion circuit and the current A / D conversion circuit are both time-interleaved analog-to-digital converters (TIADC for short).

[0017] The object of the invention of the present invention is achieved in this way:

[0018] The high-precision source measurement unit of the present invention improves the D / A conversion circuit on the basis of the prior art, adopts a low-noise amplifier Amp and four resistors to output V of two DACs. 1 、V 2 Proceed with the set scaling factor 2 N By adding, the resolution of the digital-to-analog conversion is increased by N bits, and the resolution and sampling rate of the D / A conversion circuit are greatly improved, that is, the DAC splicing technology is used to achieve high-bandwidth and high-precision signal output. At the same time, the voltage A / D conversion circuit and the current A / D conversion circuit used in the present invention are both time-interleaved analog-to-digital conversion devices, which improves the signal sampling rate, thereby improving the measurement accuracy and bandwidth. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the principle of a specific implementation of the high-precision source measurement unit of the present invention. DETAILED DESCRIPTION

[0020] The specific implementation of the present invention is described below in conjunction with the accompanying drawings so that those skilled in the art can better understand the present invention. It should be noted that in the following description, when the detailed description of known functions and designs may dilute the main content of the present invention, these descriptions will be omitted here.

[0021] Figure 1 It is a schematic diagram of the principle of a specific implementation of the high-precision source measurement unit of the present invention.

[0022] In this embodiment, if Figure 1As shown, the high-precision source measurement unit of the present invention includes a control unit 1, a D / A conversion circuit 2, an output drive circuit 3, a gear switching circuit, a voltage A / D conversion circuit 5 and a current A / D conversion circuit 6.

[0023] The control unit 1 controls the D / A conversion circuit 2 to output a precision voltage signal, which is then output to the gear switching circuit for gear switching after the output driving capability is enhanced by the output driving circuit 3, and then loaded onto the electronic device under test. The gear switching circuit includes a current gear circuit 401 and a voltage gear circuit 402.

[0024] The current range circuit 401 is composed of a current sampling resistor array 4011, a current switch matrix 4012 and a programmable instrument amplifier 4013, wherein the current sampling resistor array 4011 is used for voltage-current conversion and feedback current sampling, the precision voltage signal output by the output drive circuit 3 is loaded onto the electronic device under test 7 through the sampling resistor array 4011, the current switch matrix 4012 realizes current output range switching and current measurement range switching by selecting different sampling resistors in the current sampling resistor array 4011 to connect the path from the output drive circuit 3 to the electronic device under test 7, the programmable instrument amplifier 4013 obtains the voltage across the sampling resistor and sends it to the current A / D conversion circuit 6 for analog-to-digital conversion, obtains the current measurement value, and inputs it into the control unit 1.

[0025] The voltage range circuit 402 is composed of a voltage switch matrix 4021 and a programmable instrument amplifier 4022. The voltage switch matrix 4021 is used to select a local measurement mode or a remote measurement mode to obtain the voltage across the electronic device 7 under test. Then, the programmable instrument amplifier 4022 processes the obtained voltage and sends it to the voltage A / D conversion circuit 5 to obtain the voltage measurement value and input it into the control unit 1.

[0026] The voltage measurement accuracy is affected by the output current and the wire resistance. In the present invention, the two measurement modes are switched by the voltage switch matrix 4021. When the wiring is inconvenient, the local measurement mode can reduce the wiring overhead. When the precision measurement is required, the remote measurement mode can achieve the best measurement accuracy. The programmable instrument amplifier is used to process the feedback voltage signal.

[0027] Since the source measurement unit has many gears and a large dynamic range, a programmable instrumentation amplifier is used to process the feedback current signal. The programmable instrumentation amplifier has a high input common-mode rejection ratio, which can effectively filter out the unwanted common-mode voltage signal in the current measurement. Secondly, by adjusting the amplification factor of the programmable instrumentation amplifier, the measurement signal can be adjusted to the appropriate ADC sampling range to provide the best ADC performance and enhance the system's current measurement dynamic range.

[0028] Based on the above-mentioned prior art, in order to achieve high-bandwidth and high-precision signal output, the present invention improves the D / A conversion circuit. The D / A conversion circuit 2 mainly converts the digital voltage signal of the main control unit 1 into an analog voltage signal output. The output resolution and sampling rate of the DAC affect the accuracy and bandwidth of the source measurement unit. At the same time, the resolution and sampling rate of the DAC are contradictory. The higher the resolution, the lower the sampling rate. Therefore, the present invention can use two high-speed (high sampling rate) low-resolution DACs for splicing to obtain a high-speed and high-precision (high resolution) D / A conversion circuit 2.

[0029] Specific as Figure 1 As shown, the D / A conversion circuit 2 includes two DACs, namely DAC1 and DAC2, a low noise amplifier Amp, and four resistors R 1 , R 2 , R 3 , R 4 , the output voltage of the first DAC, DAC1, is V 1 Directly input to the positive input terminal of the low noise amplifier Amp, the second DAC output voltage is DAC2 output voltage V 2 Through the resistor R 2 Input to the negative input terminal of the low noise amplifier Amp, through the resistor R 4 Connect the output terminal of the low noise amplifier Amp to the negative input terminal. The negative input terminal of the low noise amplifier Amp is connected through the resistor R 3 to ground through resistor R 1 To the output offset adjustment voltage V CC .

[0030] The circuit transfer function is derived as follows:

[0031] (V 2 -V 1 ) / R 2 +(V cc -V 1 ) / R 1 =V 1 / R 3 +(V 1 -V o ) / R 4

[0032] R 1 *R 3 *R 4 (V 2 -V 1 )+R 2 *R 3 *R 4 (V cc -V 1 )=R 1 *R2 *R 4 *V 1 +R 1 *R 2 *R 3 (V 1 -V o )

[0033] R 1 *R 3 *R 4 *V 2 -R 1 *R 3 *R 4 *V 1 +R 2 *R 3 *R 4 *V cc -R 2 *R 3 *R 4 *V 1 =R 1 *R 2 *R 4 *V 1 +R 1 *R 2 *R 3 *V 1 -R 1 *R 2 *R 3 *V o

[0034] R 1 *R 2 *R 3 *V o =R 1 *R 2 *R 4 *V 1 +R 1 *R 2 *R 3 *V 1 -R 1 *R 3 *R 4 *V 2 +R 1 *R 3 *R 4 *V 1 -R 2 *R 3 *R 4 *V cc +R 2 *R 3 *R 4 *V1

[0035] V o =R 4 / R 3 *V 1 +V 1 -R 4 / R 2 *V 2 +R 4 / R 2 *V 1 -R 4 / R 1 *V cc +R 4 / R 1 *V 1

[0036] V o =(R 4 / R 3 +1+R 4 / R 2 +R 4 / R 1 )*V 1 -R 4 / R 2 *V 2 -R 4 / R 1 *V cc

[0037] Therefore, the actual transfer function of the circuit is the precise voltage signal V O :

[0038]

[0039] Among them, V 1 The voltage converted from the high-bit voltage value output by control unit 1, V 2 The voltage converted from the low-bit voltage value data output by the control unit 1, V CC Output offset adjustment voltage, four resistors R 1 , R 2 , R 3 , R 4 According to the set proportionality factor 2 N To confirm:

[0040] 2 N =1+R 2 / R 1 +R 2 / R 3 +R 2 / R 4

[0041] Wherein, N is the digital-to-analog conversion resolution that needs to be improved, which is a positive integer, and its value is less than or equal to the resolution of the second DAC.

[0042] When the ratio coefficient of the two DACs, DAC1 and DAC2, is 1 / 1024, the DAC resolution is increased by 10 bits, and when the ratio coefficient is 1 / 2048, the DAC resolution is increased by 11 bits. By combining two 14-bit resolution DACs, you can get 24-bit resolution and 25-bit resolution DACs respectively.

[0043] The ADC voltage and current A / D conversion circuit mainly converts the analog voltage and current signals of the output port into digital signals and sends them to the main control unit for digital processing. The output resolution and sampling rate of the A / D conversion circuit also affect the accuracy and bandwidth of the source measurement unit.

[0044] In the present invention, the voltage A / D conversion circuit 5 and the current A / D conversion circuit 6 are both time-interleaved analog-to-digital converters (TIADC for short). Figure 1 As shown, M ADCs are used to sample using time-interleaved sampling technology, and the sampling clock is provided by PLL. By adjusting the phase difference of the phase-locked loop, that is, the PLL outputs the clock to each ADC to 2π / M degrees, and then using the phase and gain calibration technology to perform ADC matching calibration, the purpose of improving the ADC sampling rate is achieved. In this embodiment, M=4, by controlling the phase difference of the PLL output clock to 90 degrees, and then calibrating the gain and sampling clock phase of the ADC by the time-interleaved sampling self-calibration technology. After the source measurement unit is powered on, the voltage A / D conversion circuit 5 and the current A / D conversion circuit 6 are calibrated in turn.

[0045] Due to the constraints of integrated circuits, the high sampling rate and high resolution of ADC cannot be achieved at the same time. For source measurement units, high sampling rate and high resolution ADC are essential. Using multiple ADCs for time-interleaved sampling can effectively improve the system sampling rate, but due to the device differences and sampling clock phase deviations between the ADCs, multiple ADCs cannot achieve accurate time-interleaved sampling. The source measurement unit is a device that integrates output and acquisition. With the help of the internal D / A conversion circuit 2, time-interleaved sampling self-calibration can be achieved. First, the D / A conversion circuit 2 is used to output a DC voltage, which is sent to the voltage A / D conversion circuit 5 and the current A / D conversion circuit 6 through the gear switching circuit 4 for collection respectively. The collected data is sent to the main control module 1 for multi-chip ADC gain calibration. Then, the D / A conversion circuit 2 is used to output a standard sine wave, and multiple ADCs are used for collection. The collected data is sent to the main control module 1 for data splicing. The spliced ​​data is compared with the standard sine wave. According to the comparison results, the sampling clock phase output by the phase-locked loop PLL to the ADC is adjusted, and finally the gain calibration and phase calibration of multi-chip ADC time-interleaved sampling are achieved. Through the above method, the sampling rates of the voltage A / D conversion circuit 5 and the current A / D conversion circuit 6 can be effectively increased to M times the sampling rate of the single-chip ADC.

[0046] In this embodiment, if Figure 1 As shown, firstly, a DC voltage signal is output through the D / A conversion circuit 2, and then the voltage switch matrix 4021 is switched to the local measurement mode, and 4 voltage ADCs are used to collect the DC voltage signal, and the DC voltage signal is sent to the main control unit 1 for gain calibration. Then, a standard sine wave signal is output through the D / A conversion circuit 2, and 4 voltage ADCs in the voltage A / D conversion circuit 5 are used to collect the sine wave voltage signal, and the sine wave voltage signal is sent to the main control unit 1 for data splicing. The spliced ​​data is compared with the original standard sine wave, and the sampling clock phase of each voltage ADC is adjusted according to the comparison result, and finally the voltage ADC time interleaved sampling self-calibration is completed. When calibrating the current ADC, first close the Kc+ and Kc- switches, introduce the grounding resistor Rc into the current link, and then use the DAC to output the DC voltage signal, and use the 4 current ADCs in the current A / D conversion circuit 6 to collect the DC voltage signal at both ends of the grounding resistor Rc, and send it to the main control unit 1 for gain calibration. Then, the standard sine wave signal is output through the DAC, and the 4 current ADCs in the current A / D conversion circuit 6 are used to collect the sine wave voltage signals at both ends of the grounding resistor Rc, and sent to the main control unit for data splicing. The spliced ​​data is compared with the original standard sine wave, and the sampling clock phase of each current ADC is adjusted according to the comparison result, and finally the current ADC time-interleaved sampling self-calibration is completed.

[0047] The source measurement unit has many current range circuits and a large dynamic range, so the automatic range function is indispensable. When the traditional parallel current range circuit is used for automatic current range switching, there will be a range switching vacuum period, i.e., a transition period, which will greatly reduce the stability and bandwidth of the system. In addition, the current sampling resistor cannot be completely isolated outside the range. For high-precision measurement, the thermal noise of the resistor is an important part that cannot be ignored. Therefore, the present invention changes the current switch matrix 4012 into a series switch matrix, such as Figure 1 shown.

[0048] In this embodiment, six switches are used to realize seven current gears, among which K1 is normally closed and can be replaced by a wire. When K1 is closed (K1 is normally closed and replaced by a wire), the current flows through R1~R7 for the I1 gear; when K2 is closed, the R1 resistor is short-circuited, and the current flows through R2~R7 for the I2 gear; when K3 is closed, the R1 and R2 resistors are short-circuited, and the current flows through R3~R7 for the I3 gear; when K4 is closed, the R1~R3 ​​resistors are short-circuited, and the current flows through R4~R7 for the I4 gear; when K5 is closed, the R1~R4 resistors are short-circuited, and the current flows through R5~R7 for the I5 gear; when K6 is closed, the R1~R5 resistors are short-circuited, and the current flows through R6 and R7 for the I6 gear; when K7 is closed, the R1~R6 resistors are short-circuited, and the current flows through R7 for the I7 gear; the gear priority is K7>K6>K5>K4>K3>K2>K1.

[0049] The source measurement unit has many current gears, and each current measurement needs to be sampled from both ends of the point sampling resistor. In order to reduce circuit overhead, the series current switch matrix is ​​upgraded, and the current gear switch matrix is ​​reused as the positive input end of the instrument amplifier. The negative input end uses a set of multiple-select multiplexers to realize the current measurement gear.

[0050] Depend on Figure 1It can be seen that the positive input of the programmable instrumentation amplifier uses the current gear switch matrix to switch the sampling point, and the negative input is realized by the matching multiplexer. The specific workflow is that when the I1 current gear is used, K1+ and K1- are closed at the same time; when the I2 current gear is used, K2+ and K2- are closed at the same time; when the I3 current gear is used, K3+ and K3- are closed at the same time; when the I4 current gear is used, K4+ and K4- are closed at the same time; when the I5 current gear is used, K5+ and K5- are closed at the same time; when the I6 current gear is used, K6+ and K6- are closed at the same time; when the I7 current gear is used, K7+ and K7- are closed at the same time. Through the above method, the gear switching transition time can be avoided, the system stability can be enhanced, the circuit measurement noise can be reduced, and the switching overhead can be reduced. Generally, the current sampling resistor array 4011 is composed of D resistors R1~RD connected in series, and the current switch matrix 4012 is composed of D pairs of switches K1+, K1-~KD+, KD-. The precision voltage signal output by the output drive circuit is loaded onto the electronic device under test through D resistors R1~RD resistors in sequence. The d pair of switches Kd+ and Kd- are connected to the front and back ends of the d resistor, wherein the input direction of the precision voltage signal is the front, and the output direction of the electronic device under test is the rear. The switch K1+ is in a normally closed state. When the Id current gear is used, the d pair of switches Kd+ and Kd- are closed, and the remaining switches except the switch K1+ are in an open state.

[0051] PID control algorithm (proportional-integral-differential controller) plays a vital role in the field of automatic control. It is a classic control strategy that is widely used in many fields such as industrial automation, robot control, flight control, temperature control, flow control, etc.

[0052] The source measurement unit can control the two parameters of output voltage and current at the same time. The current is converted from the voltage. The parameters involved in the PID loop operation are different in different working modes. For example, in the constant voltage mode, the loop control parameter is the voltage value, and the current value is used as the threshold; in the constant current mode, the loop control parameter is the current value, and the voltage value is used as the threshold. This control method is simple to implement, but there are risks in the application of source measurement units. Take the constant voltage mode as an example. The system sets the constant voltage output xV and the current limit yA. The PID algorithm will use ΔxV as the error variable. When the output current reaches the limit value but does not reach the voltage setting value, due to the lag of the PID algorithm, the system will switch back and forth between the constant voltage mode and the constant current mode under constant voltage. The output is reflected in the output ringing, which greatly reduces the stability of the system.

[0053] In this embodiment, by nesting the voltage PID and the current PID, the source measurement unit is affected by both the voltage and current parameters during control, which can enhance the stability and responsiveness of the system. Since one PID controller is nested inside another PID controller during control, the two PID controllers are named outer loop PID controller and inner loop PID controller respectively. The following symbols are used to represent the PID controller.

[0054] Outer Loop PID Controller

[0055] Setting value: r outer (t);

[0056] Actual value: y outer (t);

[0057] Output: u outer (t);

[0058] Inner loop PID controller

[0059] Setting value: r inner (t) = u outer (t);

[0060] Actual value: y inner (t);

[0061] Output: u inner (t);

[0062] Outer Loop PID Controller Formula

[0063] where e outer (t) = r outer (t)-y outer (t).

[0064] Inner loop PID controller formula

[0065] where e inner (t) = r inner (t)-y inner (t).

[0066] The control flow is as follows:

[0067] The outer loop PID controller receives the setpoint r outer and the actual output y outer , calculation error e outer ;

[0068] The outer loop PID controller is based on the error e outer Calculate the output u outer, and use it as the setting value r of the inner loop PID controller inner ;

[0069] The inner loop PID controller receives the setpoint r inner and the actual output y inner , calculation error e inner ;

[0070] The inner loop PID controller is based on the error e inner Calculate the output u inner , and use it as the final control signal.

[0071] In different application scenarios, the parameters of the inner and outer loop PID controllers can be changed flexibly.

[0072] In this embodiment, inner and outer loop PID controllers are provided in the main control module 1. In the constant voltage mode, the setting value of the outer loop PID controller is the voltage setting value, and the actual value is the measured voltage value of the electronic device under test. The output value of the outer loop PID controller is used as the setting value of the inner loop PID controller, and the actual value is the difference between the current limiting value and the measured current value of the electronic device under test. The output value of the inner loop PID controller is sent to the output drive circuit 3 as the final control signal.

[0073] In the constant current mode, the setting value of the outer loop PID controller is the current setting value, and the actual value is the measured current value of the electronic device under test. The output value of the outer loop PID controller is used as the setting value of the inner loop PID controller, and the actual value is the difference between the voltage limit value and the measured voltage value of the electronic device under test. The output value of the inner loop PID controller is sent to the output drive circuit 3 as the final control signal.

[0074] In this embodiment, if Figure 1 As shown, the host computer 8 is mainly used to run the host computer software, set the voltage value, current value, gear, loop response speed and other parameters in the software, and then send them to the main control unit 8 through the PXIe bus protocol. The voltage value of the voltage A / D conversion circuit 5 and the current value collected by the current A / D conversion circuit 6 will also be uploaded to the host computer through the PXIe bus for display and storage.

[0075] Although the above describes the illustrative specific embodiments of the present invention to facilitate those skilled in the art to understand the present invention, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations using the concept of the present invention are protected.

Claims

1. A high-precision source measurement unit, comprising a control unit, a D / A conversion circuit, an output drive circuit, a gear switching circuit, a voltage A / D conversion circuit and a current A / D conversion circuit; The control unit controls the D / A conversion circuit to output a precision voltage signal, which is then output to the gear switching circuit for gear switching after the output drive circuit enhances the output drive capability, and then loaded onto the electronic device under test; in, The gear switching circuit includes a current gear circuit and a voltage gear circuit; The current range circuit is composed of a current sampling resistor array, a current switch matrix and a programmable instrument amplifier, wherein the current sampling resistor array is used for voltage-current conversion and feedback current sampling, the precision voltage signal output by the output drive circuit is loaded onto the electronic device under test through the sampling resistor array, the current switch matrix realizes current output range switching and current measurement range switching by selecting different sampling resistors in the current sampling resistor array to access the path from the output drive circuit to the electronic device under test, and the programmable instrument amplifier obtains the voltage across the sampling resistor and sends it to the current A / D conversion circuit for analog-to-digital conversion to obtain the current measurement value and input it into the control unit; The voltage range circuit is composed of a voltage switch matrix and a programmable instrument amplifier. The voltage switch matrix is ​​used to select a local measurement mode or a remote measurement mode to obtain the voltage across the electronic device under test. Then, the programmable instrument amplifier processes the obtained voltage and sends it to the voltage A / D conversion circuit to obtain the voltage measurement value and input it into the control unit. The D / A conversion circuit includes two DACs, a low noise amplifier and four resistors R1, R2, R3 and R4. The output voltage of the first DAC is directly input to the positive input terminal of the low noise amplifier. The output voltage of the second DAC is input to the negative input terminal of the low noise amplifier through the resistor R2. The output terminal of the low noise amplifier is connected to the negative input terminal through the resistor R4. The negative input terminal of the low noise amplifier is connected to the ground through the resistor R3 and to the output offset adjustment voltage V through the resistor R1. CC , get the precise voltage signal V O : Among them, V1 is the voltage converted from the high-bit voltage value data output by the control unit, V2 is the voltage converted from the low-bit voltage value data output by the control unit, V CC The output offset adjusts the voltage. The four resistors R1, R2, R3, and R4 are set according to the proportional coefficient 2. N To confirm: 2 N =1+R2 / R1+R2 / R3+R2 / R4 Wherein, N is the digital-to-analog conversion resolution that needs to be improved, which is a positive integer, and its value is less than or equal to the resolution of the second DAC; The voltage A / D conversion circuit and the current A / D conversion circuit are both time-interleaved analog-to-digital conversion devices.

2. The high-precision source measurement unit according to claim 1, characterized in that: The current sampling resistor array is composed of D resistors R1~RD resistors connected in series, and the current switch matrix is ​​composed of D pairs of switches K1+, K1-~KD+, KD-. The precision voltage signal output by the output drive circuit is loaded onto the electronic device under test through D resistors R1~RD resistors in sequence. The dth pair of switches Kd+ and Kd- are connected to the front and back ends of the dth resistor, wherein the input direction of the precision voltage signal is the front, and the output direction of the electronic device under test is the rear. The switch K1+ is in a normally closed state. When the Id current gear is used, the dth pair of switches Kd+ and Kd- are closed, and the remaining switches except the switch K1+ are in an open state.

3. The high-precision source measurement unit according to claim 1, characterized in that: The main control module is provided with inner and outer loop PID controllers. In constant voltage mode, the setting value of the outer loop PID controller is the voltage setting value, and the actual value is the measured voltage value of the electronic device under test. The output value of the outer loop PID controller is used as the setting value of the inner loop PID controller, and the actual value is the difference between the current limiting value and the measured current value of the electronic device under test. The output value of the inner loop PID controller is sent to the output drive circuit as the final control signal; in constant current mode, the setting value of the outer loop PID controller is the current setting value, and the actual value is the measured current value of the electronic device under test. The output value of the outer loop PID controller is used as the setting value of the inner loop PID controller, and the actual value is the difference between the voltage limiting value and the measured voltage value of the electronic device under test. The output value of the inner loop PID controller is sent to the output drive circuit as the final control signal.

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