A precision micro-current source

Abstract

The application discloses a kind of precision tiny current sources.The current source includes: constant voltage source module, voltage division module and constant current source module in series in turn;Constant voltage source module is used to provide constant reference voltage;Voltage division module is used to carry out voltage division based on calibrated voltage ratio to the constant reference voltage, and obtain constant calibration voltage;Constant current source module is used to generate the current of different constant current value based on constant calibration voltage to provide for automated test equipment.The application can stabilize the output of different constant current value high-precision current, compared with commercial high-precision current source chip, greatly reduce the cost, provide high-precision, low-cost current source for semiconductor chip mass production test, especially suitable for the high-end chip test scene of harsh current precision requirement.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor chip testing, and more specifically, relates to a precise micro current source. Background Art

[0002] Performance testing of semiconductor chips (such as sensors and analog integrated circuits) requires precisely controlled current input, especially for low-power chips or high-precision devices, which often require constant current sources in the μA (microampere) or even nA (nanoampere) range. For example, sensitivity calibration of sensor chips requires a nA bias current; leakage current testing of analog circuits relies on a μA constant current source; and power consumption evaluation of low-power chips requires a stable, low-current input.

[0003] The built-in VI source of traditional automated test equipment (ATE) has the following shortcomings:

[0004] Insufficient accuracy: The current output accuracy of conventional ATE is usually ±1% to ±5%, which cannot meet the initial accuracy requirement of ±0.1% in chip testing;

[0005] Limited resolution: It is difficult to stably output nA-level current, and the current fluctuation (noise) is large;

[0006] Single function: Unable to flexibly switch between multiple current levels or adapt to different chip test scenarios.

[0007] Existing constant current sources built using resistor dividers and standard op amps are susceptible to temperature drift. For example, the resistor temperature coefficient causes current fluctuations. Especially in nanoamp-level applications, a temperature change of 0.1°C can result in errors of several nanoamps. The op amp's offset voltage (e.g., standard op amps have offset voltages in the millivolt range) and nanoamp bias currents can introduce significant errors, making them incapable of meeting precision requirements. Furthermore, commercial precision current source chips are expensive and have fixed output ranges, making them difficult to flexibly adjust to meet test requirements.

[0008] The information disclosed in the background technology section of the present invention is only intended to deepen the understanding of the general background technology of the present invention, and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art. Summary of the Invention

[0009] The purpose of this invention is to propose a precise micro current source to solve the problems of insufficient accuracy of ATE equipment and poor stability of discrete solutions. It can stably output high-precision currents with different constant current values. Compared with commercial high-precision current source chips, it greatly reduces the cost and provides a high-precision, low-cost current source for mass production testing of semiconductor chips. It is particularly suitable for high-end chip testing scenarios with stringent requirements on current accuracy.

[0010] To achieve the above objectives, the present invention proposes a precise micro current source for use in automated testing equipment. The current source comprises:

[0011] A constant voltage source module, a voltage divider module and a constant current source module connected in series in sequence;

[0012] The constant voltage source module is used to provide a constant reference voltage;

[0013] The voltage dividing module is used to divide the constant reference voltage based on the calibrated voltage ratio to obtain a constant calibration voltage;

[0014] The constant current source module is used to generate currents with different constant current values ​​based on a constant calibration voltage to provide the currents to automated testing equipment.

[0015] Optionally, the constant voltage source module includes:

[0016] A reference voltage source, a first operational amplifier, a first resistor, a second resistor, a third resistor, and a capacitor;

[0017] The output end of the reference voltage source is electrically connected to the non-inverting input end of the first operational amplifier; one end of the first resistor is electrically connected to the output end of the first operational amplifier, and the other end is electrically connected to the input end of the voltage divider module; one end of the capacitor is electrically connected to the inverting input end of the first operational amplifier through the second resistor, and the other end is electrically connected to the input end of the voltage divider module; one end of the third resistor is electrically connected to the inverting input end of the first operational amplifier, and the other end is electrically connected to the input end of the voltage divider module.

[0018] Optionally, the voltage dividing module includes:

[0019] a fourth resistor, a precision digital potentiometer, and a fifth resistor;

[0020] One end of the fourth resistor is electrically connected to the output end of the constant voltage source module, and the other end is electrically connected to the first fixed end of the precision digital potentiometer; the second fixed end of the precision digital potentiometer is electrically connected to one end of the fifth resistor, and the other end of the fifth resistor is grounded; the output end of the voltage divider module is arranged between the fourth resistor and the precision digital potentiometer;

[0021] The precision digital potentiometer is communicatively connected to the automated test equipment so that the sliding end of the precision digital potentiometer can be controlled by the automated test equipment to slide, and the position of the sliding end of the precision digital potentiometer can be read and sent to the automated test equipment for recording.

[0022] Optionally, the constant current source module includes:

[0023] a first control switch, a second control switch, a third control switch, an instrumentation amplifier, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, and a second operational amplifier;

[0024] A first input terminal of the first control switch is electrically connected to the output terminal of the voltage divider module, a second input terminal of the first control switch is electrically connected to one end of a sixth resistor, and the other end of the sixth resistor is grounded;

[0025] The non-inverting input terminal of the instrument amplifier is electrically connected to the output terminal of the first control switch, the inverting input terminal of the instrument discharger is electrically connected to one end of the seventh resistor, and the other end of the seventh resistor is grounded;

[0026] an input end of the second control switch electrically connected to the output end of the instrumentation amplifier, a first output end of the second control switch connected to one end of the eighth resistor, a second output end of the second control switch connected to one end of the ninth resistor, and a third output end of the second control switch connected to one end of the tenth resistor;

[0027] The other ends of the eighth resistor, the ninth resistor, and the tenth resistor are electrically connected to the input end of the third control switch and the non-inverting input end of the second operational amplifier;

[0028] The inverting input terminal of the second operational amplifier is electrically connected to its output terminal, and the output terminal of the second operational amplifier is electrically connected to the output reference terminal of the instrumentation amplifier;

[0029] The first output end of the third control switch is electrically connected to the output channel of the constant current source module, and the second output end of the third control switch is electrically connected to the calibration channel of the constant current source module.

[0030] Optionally, the constant current source module further includes:

[0031] a third operational amplifier, having a non-inverting input terminal electrically connected to the other ends of the eighth resistor, the ninth resistor, and the tenth resistor, an inverting input terminal electrically connected to the output terminals thereof, and an output terminal electrically connected to the current source protection signal output pin;

[0032] The current source protection signal output pin is electrically connected to a protection ring surrounding an output channel and a calibration channel of the constant current source module.

[0033] Optionally, the current source further includes:

[0034] The temperature sensor is connected to the automated test equipment for collecting temperature data of the reference voltage source and sending the temperature data to the automated test equipment.

[0035] Optionally, the current source further includes:

[0036] The memory chip is connected to the automated test equipment for storing the position of the sliding end of the precision digital potentiometer corresponding to the calibrated voltage divider ratio sent by the automated test equipment and the temperature data during calibration.

[0037] Optionally, the reference voltage source includes:

[0038] 0.5V reference voltage source chip with an accuracy of 0.35%.

[0039] Optionally,

[0040] The resistance of the fourth resistor is 200 kΩ, and the resistance tolerance is 0.1%;

[0041] The maximum resistance of the precision digital potentiometer is 20kΩ, and the resistance tolerance is 1%;

[0042] The resistance of the fifth resistor is 191 kΩ, and the resistance tolerance is 0.1%.

[0043] Optionally, the resistance values ​​of the eighth resistor, the ninth resistor and the tenth resistor are 25 kΩ, 250 kΩ and 2.5 MΩ respectively, and the resistance tolerance is 0.1%.

[0044] The beneficial effects of the present invention are as follows: the present invention provides a highly stable constant reference voltage through a constant voltage source module, laying the foundation for reference accuracy; the voltage divider module divides the reference voltage output by the constant voltage source module based on calibrated parameters to generate a high-precision constant calibration voltage, further improving voltage accuracy; the constant current source module utilizes the constant calibration voltage output by the voltage divider module to generate precise micro currents with different constant current values, and supplies them to automated testing equipment; the present invention can stably output high-precision currents with different constant current values, which greatly reduces the cost compared to commercial high-precision current source chips, and provides a high-precision, low-cost current source for mass production testing of semiconductor chips, and is particularly suitable for high-end chip testing scenarios with stringent requirements on current accuracy.

[0045] The system of the present invention has other features and advantages that will be apparent from or will be described in detail in the accompanying drawings and subsequent detailed description incorporated herein, which together serve to explain the specific principles of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings, in which like reference numerals generally represent like components.

[0047] Figure 1 A schematic diagram of a precision micro current source according to embodiment 1 of the present invention is shown. DETAILED DESCRIPTION

[0048] The present invention will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention may be implemented in various forms and is not limited to the embodiments set forth herein. Rather, these embodiments are provided to make the present invention more thorough and complete and to fully convey the scope of the present invention to those skilled in the art.

[0049] Example 1

[0050] like Figure 1 As shown, the present invention provides a precise micro current source for use in automated testing equipment, the current source comprising:

[0051] A constant voltage source module, a voltage divider module and a constant current source module connected in series in sequence;

[0052] The constant voltage source module is used to provide a constant reference voltage;

[0053] The voltage divider module is used to divide the constant reference voltage based on the calibrated voltage ratio to obtain a constant calibration voltage;

[0054] The constant current source module is used to generate currents of different constant current values ​​based on a constant calibration voltage to provide them to automated test equipment.

[0055] Specifically, the precision micro-current source device of this embodiment adopts a series architecture of a constant voltage source module, a voltage divider module and a constant current source module, and realizes high-precision current output through modular design; the constant voltage source module is the energy cornerstone of the entire device, and its core task is to provide a stable and accurate constant reference voltage for the subsequent circuit; the voltage divider module receives the constant reference voltage output by the constant voltage source module, and based on the calibrated voltage ratio, accurately divides the reference voltage to obtain a constant calibration voltage that meets the requirements of the constant current source module; the module is mainly composed of a precision resistor network. These resistors have been strictly screened and calibrated, and have extremely low temperature coefficients and extremely high resistance accuracy. The resistance error is usually controlled within ±0.05%; by reasonably configuring the connection method and resistance ratio of the resistor network, accurate voltage division of the constant reference voltage can be achieved; the calibration process usually uses a high-precision voltage measuring instrument to fine-tune the resistance of the resistor network by comparing it with a standard voltage source to ensure that the constant calibration voltage after voltage division has extremely high accuracy. The constant current source module is a key component in achieving precise output of minute currents. Based on the constant calibration voltage provided by the voltage divider module, it generates currents of varying constant current values ​​to meet the diverse testing requirements of automated test equipment. Through the precise design and coordinated operation of each module, it can stably output high-precision currents of varying constant current values. This significantly reduces costs compared to commercially available high-precision current source chips, providing a high-precision, low-cost current source for mass production testing of semiconductor chips. It is particularly suitable for testing high-end chips with demanding current accuracy requirements.

[0056] In this embodiment, the constant voltage source module includes:

[0057] A reference voltage source REF, a first operational amplifier AMP1, a first resistor R1, a second resistor R2, a third resistor R3 and a capacitor C1;

[0058] The output end of the reference voltage source REF is electrically connected to the non-inverting input end of the first operational amplifier AMP1; one end of the first resistor R1 is electrically connected to the output end of the first operational amplifier AMP1, and the other end is electrically connected to the input end of the voltage divider module; one end of the capacitor C1 is electrically connected to the inverting input end of the first operational amplifier AMP1 through the second resistor R2, and the other end is electrically connected to the input end of the voltage divider module; one end of the third resistor R3 is electrically connected to the inverting input end of the first operational amplifier AMP1, and the other end is electrically connected to the input end of the voltage divider module.

[0059] Specifically, the output of the reference voltage source REF is directly connected to the non-inverting input of the first operational amplifier AMP1, providing a stable voltage reference for the first operational amplifier AMP1 and ensuring the accuracy of subsequent signal processing. The reference voltage source REF uses a 0.5V reference voltage source chip, providing a stable 0.5V reference voltage with an accuracy of 0.35%. The GND pin of the reference voltage source REF is directly connected to the GND of the circuit board to ensure a stable ground potential in the reference source area. The first operational amplifier AMP1, the first resistor R1, the second resistor R2, the third resistor R3, and the capacitor C1 form a precision reference voltage buffer circuit, providing a precise buffered output with sufficient drive current for transient changes, capable of filtering out high-frequency interference, and ensuring the purity of the reference voltage. This buffer circuit is essentially a voltage follower topology, centered around the first operational amplifier AMP1. The first amplifier has a high input impedance, which minimizes the loading effect on the reference voltage source REF when it receives a signal, ensuring the stability of the reference voltage source's output. It also has a low output impedance, providing stable driving capability for subsequent circuits. When connected to varying loads, this low output impedance keeps the output voltage relatively stable, preventing significant fluctuations due to load variations. The second and third resistors R2 and R3 form a DC feedback loop. Due to the operational amplifier's "virtual short" characteristic (the voltages at the non-inverting and inverting inputs are approximately equal), changes in the feedback voltage occur when the output voltage changes. Through the amplification of the first operational amplifier AMP1, the output voltage is adjusted to approach the reference voltage, achieving a stable DC output voltage. For example, if the output voltage increases, the voltage at the inverting input increases, causing the output voltage of the first operational amplifier AMP1 to decrease, and vice versa. Capacitor C1 is a compensation capacitor. Together with resistor R2, it forms a hysteresis compensation network. By introducing phase lag, it offsets the phase lag generated by the internal pole of the first operational amplifier AMP1, preventing circuit oscillation due to low phase margin. Capacitor C1 presents low impedance to high-frequency noise, short-circuiting it to ground and suppressing high-frequency interference in the reference voltage. During step changes in the reference voltage, capacitor C1 controls the rate of change of the feedback signal through its charge and discharge process with resistor R2, preventing overshoot or oscillation in the output of the first operational amplifier AMP1 and shortening the time it takes for the circuit to reach a stable value. Resistor R1 limits the current flowing to the voltage divider module, protecting the first operational amplifier AMP1. Resistor R1 and capacitor C1 form a low-pass filter. The constant voltage source module achieves high-precision transmission of the reference voltage and noise suppression through the buffering effect of the first operational amplifier AMP1 and the filtering properties of the RC network. Its core principle is to utilize the virtual short and virtual open characteristics of the op amp to create a stable feedback network, while capacitor C1 effectively attenuates high-frequency noise.

[0060] In this embodiment, the voltage divider module includes:

[0061] A fourth resistor R4, a precision digital potentiometer RP1 and a fifth resistor R5;

[0062] One end of the fourth resistor R4 is electrically connected to the output end of the constant voltage source module, and the other end is electrically connected to the first fixed end of the precision digital potentiometer RP1; the second fixed end of the precision digital potentiometer RP1 is electrically connected to one end of the fifth resistor R5, and the other end of the fifth resistor R5 is grounded; the output end V1 of the voltage divider module is provided between the fourth resistor R4 and the precision digital potentiometer RP1;

[0063] The precision digital potentiometer RP1 is communicatively connected to the automated testing equipment so as to control the sliding of the sliding end of the precision digital potentiometer RP1 through the automated testing equipment, and read the position of the sliding end of the precision digital potentiometer RP1 and send it to the automated testing equipment for recording.

[0064] Specifically, the precision digital potentiometer RP1 is a 256-bit precision digital potentiometer. Essentially, it is a variable resistor whose resistance can be controlled by a digital signal. By changing the internal connections via the digital control signal, the resistance can be adjusted continuously or in steps within a certain range. In this embodiment, the precision digital potentiometer RP1 communicates with the automated test equipment via the I2C_SDA and I2C_SCL interfaces. This receives digital signals from the automated test equipment, adjusts the resistance by changing the position of the precision digital potentiometer's slider, and transmits the final slider position to the automated test equipment via a digital signal for recording. The position of the slider of the precision digital potentiometer is adjusted by the control circuit CONTROL within the precision digital potentiometer.

[0065] In this embodiment, the constant current source module includes:

[0066] a first control switch SW1, a second control switch SW2, a third control switch SW3, an instrumentation amplifier INA, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, and a second operational amplifier AMP2;

[0067] A first input terminal of the first control switch SW1 is electrically connected to the output terminal V1 of the voltage divider module, a second input terminal of the first control switch SW1 is electrically connected to one end of the sixth resistor R6, and the other end of the sixth resistor R6 is grounded;

[0068] The non-inverting input terminal of the instrumentation amplifier INA is electrically connected to the output terminal of the first control switch SW1, the inverting input terminal of the instrumentation discharger is electrically connected to one end of the seventh resistor R7, and the other end of the seventh resistor R7 is grounded;

[0069] An input end of the second control switch SW2 is electrically connected to an output end of the instrumentation amplifier INA, a first output end of the second control switch SW2 is connected to one end of the eighth resistor R8, a second output end of the second control switch SW2 is connected to one end of the ninth resistor R9, and a third output end of the second control switch SW2 is connected to one end of the tenth resistor R10;

[0070] The other ends of the eighth resistor R8, the ninth resistor R9 and the tenth resistor R10 are electrically connected to the input end of the third control switch SW3 and the non-inverting input end of the second operational amplifier AMP2;

[0071] The inverting input terminal of the second operational amplifier AMP2 is electrically connected to its output terminal, and the output terminal thereof is electrically connected to the output reference terminal REF of the instrumentation amplifier INA;

[0072] A first output end of the third control switch SW3 is electrically connected to the output channel I_SRC_OUT of the constant current source module, and a second output end of the third control switch SW3 is electrically connected to the calibration channel I_SRC_CAL of the constant current source module.

[0073] Specifically, the first control switch SW1 is used to turn the constant current source output on and off. This first control switch SW1 switches the input signal, selecting either the voltage divider signal at the voltage divider module output terminal V1 or the ground signal (low level) at R6. The instrumentation amplifier INA amplifies the voltage divider signal output from the voltage divider module output terminal V1, while suppressing any interference from ambient noise. It also isolates the pre- and post-stage circuits to prevent variations in the post-stage resistor network from affecting the pre-stage voltage divider ratio. The second control switch SW2 switches the eighth, ninth, and tenth resistors R8, R9, and R10 to select different constant current values. The inverting input of the second operational amplifier AMP2 is connected to its output, forming a closed-loop feedback structure in the form of a voltage follower. This structure stabilizes signal gain, ensuring the stability and accuracy of the output signal. The output of the second operational amplifier AMP2 is connected to the output reference terminal REF of the instrumentation amplifier INA. The output characteristics of the instrumentation amplifier INA ensure that the voltage difference between its output terminal and the output reference terminal REF is always equal to the input voltage. The current formed by this voltage difference across the eighth resistor R8, the ninth resistor R9, or the tenth resistor R10 is the output constant current value. Because the input of the second operational amplifier AMP2 is high-impedance, the bias current is extremely small and does not affect the accuracy of the output constant current value. The output channel I_SRC_OUT and the calibration channel I_SRC_CAL of the constant current source module are switched via the third control switch SW3 to cooperate with the automated test equipment for normal testing or calibration of the output current value.

[0074] In this embodiment, the constant current source module further includes:

[0075] a third operational amplifier AMP3, having a non-inverting input terminal electrically connected to the other ends of the eighth resistor R8, the ninth resistor R9, and the tenth resistor R10, an inverting input terminal electrically connected to the output terminals thereof, and an output terminal electrically connected to the current source protection signal output pin I_SRC_GUARD;

[0076] The current source protection signal output pin I_SRC_GUARD is electrically connected to a guard ring GUARD_RING surrounding an output channel and a calibration channel of the constant current source module.

[0077] Specifically, the non-inverting input terminal of the third operational amplifier AMP3 directly samples the output voltage of the constant current source module, and its inverting input terminal is short-circuited with its output terminal to form a voltage follower structure, and its output terminal is connected to the protection ring GUARD_RING on the circuit board through the current source protection signal output pin I_SRC_GUARD, and the protection ring GUARD_RING surrounds the output channel I_SRC_OUT and the calibration channel I_SRC_CAL of the constant current source module; the third operational amplifier AMP3 is used to generate a current source protection signal, and its output voltage is equal to the output voltage of the constant current source module. Therefore, the protection ring GUARD_RING maintains a constant potential with the output signal of the constant current source module, and the output channel I_SRC_OUT and the calibration channel I_SRC_CAL will not generate accidental leakage to the surrounding environment of the circuit board, thereby ensuring the output accuracy of the constant current source module.

[0078] In this embodiment, the precision micro current source further includes:

[0079] The temperature sensor is connected to the automated test equipment for communication, and is used for collecting temperature data of the reference voltage source REF and sending the temperature data to the automated test equipment.

[0080] Specifically, a temperature sensor is arranged close to a reference voltage source REF, and the temperature data of the reference voltage source REF is used. The temperature data is then sent to an automated test device to compensate for voltage drift.

[0081] In this embodiment, the precision micro current source further includes:

[0082] The storage chip EEPROM is connected to the automated test equipment for storing the position of the sliding end of the precision digital potentiometer RP1 corresponding to the calibrated voltage divider ratio sent by the automated test equipment and the temperature data during calibration.

[0083] In this embodiment, the reference voltage source REF uses a 0.5V reference voltage source chip with an accuracy of 0.35%. The fourth resistor R4 has a resistance of 200kΩ and a resistance tolerance of 0.1%. The precision digital potentiometer RP1 has a maximum resistance of 20kΩ and a resistance tolerance of 1%. The fifth resistor R5 has a resistance of 191kΩ and a resistance tolerance of 0.1%. The eighth resistor R8, ninth resistor R9, and tenth resistor R10 have resistances of 25kΩ, 250kΩ, and 2.5MΩ, respectively, all with a resistance tolerance of 0.1%.

[0084] Specifically, based on the output voltage value and accuracy of the reference voltage source REF, the resistance values ​​and resistance tolerances of the fourth resistor R4, the fifth resistor R5, the eighth resistor R8, the ninth resistor R9, and the tenth resistor R10, and the maximum resistance value and resistance tolerance of the precision digital potentiometer RP1, the maximum and minimum voltage outputted from the output terminal V1 of the voltage divider module can be calculated (the offset voltage of the budget amplifier 10uV can be ignored, and the input bias current of the budget amplifier 10pA can be ignored); the maximum voltage = (5 1.0035) (20 1.01+191 1.001) / (200 0.999+20 1.01+191 1.001) = 2.5795V; minimum voltage = (5 0.9965) (191 0.999) / (200 1.001+191 0.999) = 2.4314V; the maximum offset voltage of the instrumentation amplifier (INA) is + / -180uV, and the current source resistor tolerance is 0.1%. The maximum and minimum adjustable ranges of the three current values ​​are as follows:

[0085] 10uA: Maximum current = (2.5795V + 180uV) / (25K 0.999)=10.329uA, minimum current=(2.4314V-180uV) / (25K 1.001)=9.7151uA;

[0086] 1uA: Maximum current = (2.5795V + 180uV) / (250K 0.999)=1.0329uA, minimum current=(2.4314V-180uV) / (250K 1.001)=0.97151uA;

[0087] 100nA: Maximum current = (2.5795V + 180uV) / (2.5M 0.999)=103.29nA, minimum current=(2.4314V-180uV) / (2.5M 1.001)=97.151nA;

[0088] After adjusting the 256-bit precision digital potentiometer RP1, the minimum adjustment step of each current value is (10.329-9.7151) / 256 / 10 100%=0.024%.

[0089] In this embodiment, the third control switch SW3 is switched to the constant current source module's calibration channel I_SRC_CAL, connecting the module's output to the ATE's high-precision multimeter to form a calibration measurement loop. The first control switch SW1 is controlled to always keep the constant current source output on, ensuring that the current output by the constant current source module flows through the calibration path. The 256-bit digital potentiometer RP1 has 256 adjustable positions (0-255). By using a "binary search" method, the adjustment range is reduced by half each time. After a maximum of eight attempts, the potentiometer position closest to the target current value (10uA / 1uA / 100nA) is found and stored in the EEPROM memory chip. For example, during the first adjustment, the potentiometer's initial position is set to 128 (the middle value), and the current I1 is measured. If I1 < 10μA, the V1 voltage needs to be increased, and the next adjustment position is set to 192 (128 + 64). If I1 > 10μA, the potentiometer position is set to 64 (128 - 64). Second adjustment: Based on the last deviation, continue to reduce the range by half (such as 192→224 or 192→160) until the current approaches the target value. A maximum of 8 adjustments: = 256, covering all potentiometer positions, ultimately achieving a current error of ≤±0.1%. During calibration, the ATE reads the real-time temperature value from the temperature sensor and stores it in the on-chip EEPROM for subsequent temperature drift compensation. The EEPROM stores the optimal potentiometer position for each setting (e.g., 10μA corresponds to position 200) as well as the temperature value at the time of calibration. When multiple current sources are required for chip testing, the ATE can independently access the EEPROM for each current source, read the corresponding calibration data, and write it to the corresponding digital potentiometer. This ensures that the output current accuracy of multiple current sources simultaneously matches the accuracy at the time of calibration. The current circuit environment temperature is also read and compared with the calibration temperature. The difference between the current and calibration temperatures compensates for voltage drift in the reference voltage source REF, eliminating the need for repeated calibration and quickly achieving the same accuracy for multiple current sources. This calibration mechanism, through a combination of hardware adjustment, software algorithm, and temperature compensation, achieves high-precision calibration of low currents (10μA / 1μA / 100nA). The core logic is to use a digital potentiometer to fine-tune the voltage, combined with the dichotomy method to quickly converge to the target current, and use EEPROM and temperature sensors to ensure the long-term validity and environmental adaptability of the calibration data, solving the problem of precise control of tiny currents in semiconductor chip testing.

[0090] While various embodiments of the present invention have been described above, the above description is intended to be illustrative, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A precision micro current source, used in automated testing equipment, characterized in that: The current source comprises: A constant voltage source module, a voltage divider module and a constant current source module connected in series in sequence; The constant voltage source module is used to provide a constant reference voltage; The voltage dividing module is used to divide the constant reference voltage based on the calibrated voltage ratio to obtain a constant calibration voltage; The constant current source module is used to generate currents of different constant current values ​​based on a constant calibration voltage to provide to automated testing equipment; The constant current source module includes: a first control switch, a second control switch, a third control switch, an instrumentation amplifier, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, and a second operational amplifier; A first input terminal of the first control switch is electrically connected to the output terminal of the voltage divider module, a second input terminal of the first control switch is electrically connected to one end of a sixth resistor, and the other end of the sixth resistor is grounded; The non-inverting input terminal of the instrumentation amplifier is electrically connected to the output terminal of the first control switch, the inverting input terminal of the instrumentation amplifier is electrically connected to one end of the seventh resistor, and the other end of the seventh resistor is grounded; an input end of the second control switch electrically connected to the output end of the instrumentation amplifier, a first output end of the second control switch connected to one end of the eighth resistor, a second output end of the second control switch connected to one end of the ninth resistor, and a third output end of the second control switch connected to one end of the tenth resistor; The other ends of the eighth resistor, the ninth resistor, and the tenth resistor are electrically connected to the input end of the third control switch and the non-inverting input end of the second operational amplifier; The inverting input terminal of the second operational amplifier is electrically connected to its output terminal, and the output terminal of the second operational amplifier is electrically connected to the output reference terminal of the instrumentation amplifier; The first output end of the third control switch is electrically connected to the output channel of the constant current source module, and the second output end of the third control switch is electrically connected to the calibration channel of the constant current source module.

2. The precision micro current source according to claim 1, characterized in that: The constant voltage source module includes: A reference voltage source, a first operational amplifier, a first resistor, a second resistor, a third resistor, and a capacitor; The output end of the reference voltage source is electrically connected to the non-inverting input end of the first operational amplifier; one end of the first resistor is electrically connected to the output end of the first operational amplifier, and the other end is electrically connected to the input end of the voltage divider module; one end of the capacitor is electrically connected to the inverting input end of the first operational amplifier through the second resistor, and the other end is electrically connected to the input end of the voltage divider module; one end of the third resistor is electrically connected to the inverting input end of the first operational amplifier, and the other end is electrically connected to the input end of the voltage divider module.

3. The precision micro current source according to claim 2, characterized in that: The voltage divider module includes: a fourth resistor, a precision digital potentiometer, and a fifth resistor; One end of the fourth resistor is electrically connected to the output end of the constant voltage source module, and the other end is electrically connected to the first fixed end of the precision digital potentiometer; the second fixed end of the precision digital potentiometer is electrically connected to one end of the fifth resistor, and the other end of the fifth resistor is grounded; the output end of the voltage divider module is arranged between the fourth resistor and the precision digital potentiometer; The precision digital potentiometer is communicatively connected to the automated test equipment so that the sliding end of the precision digital potentiometer can be controlled by the automated test equipment to slide, and the position of the sliding end of the precision digital potentiometer can be read and sent to the automated test equipment for recording.

4. The precision micro current source according to claim 3, characterized in that: The constant current source module further includes: a third operational amplifier, having a non-inverting input terminal electrically connected to the other ends of the eighth resistor, the ninth resistor, and the tenth resistor, an inverting input terminal electrically connected to the output terminals thereof, and an output terminal electrically connected to the current source protection signal output pin; The current source protection signal output pin is electrically connected to a protection ring surrounding an output channel and a calibration channel of the constant current source module.

5. The precision micro current source according to claim 4, characterized in that: The current source further comprises: The temperature sensor is connected to the automated test equipment for collecting temperature data of the reference voltage source and sending the temperature data to the automated test equipment.

6. The precision micro current source according to claim 5, characterized in that: The current source further comprises: The memory chip is connected to the automated test equipment for storing the position of the sliding end of the precision digital potentiometer corresponding to the calibrated voltage divider ratio sent by the automated test equipment and the temperature data during calibration.

7. The precision micro current source according to claim 2, characterized in that: The reference voltage source comprises: 0.5V reference voltage source chip with an accuracy of 0.35%.

8. The precision micro current source according to claim 3, characterized in that: The resistance of the fourth resistor is 200 kΩ, and the resistance tolerance is 0.1%; The maximum resistance of the precision digital potentiometer is 20kΩ, and the resistance tolerance is 1%; The resistance of the fifth resistor is 191 kΩ, and the resistance tolerance is 0.1%.

9. The precision micro current source according to claim 1, characterized in that: The resistance values ​​of the eighth resistor, the ninth resistor and the tenth resistor are 25 kΩ, 250 kΩ and 2.5 MΩ respectively, and the resistance tolerance is 0.1%.

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