Wide range programmable current excitation test circuit for temperature sensor

Abstract

The utility model relates to a wide range program control current excitation test circuit of temperature sensor, including chip U2, chip U3, chip U4, chip U2 is instrument operational amplifier, chip U3 is digital analog converter of IIC signal conversion analog current signal, chip U4 is zener diode type temperature sensor, the utility model relates to through program control current can automatically, fastly carry out the test evaluation of full working current range to chip. This makes production test can cover the diversified application scene of different customers, ensures that the chip of shipment can stably work in 0.4mA to 5mA working current range, has greatly promoted the applicability and reliability of final product.

Description

Technical Field

[0001] This utility model relates to a wide-range programmable current excitation test circuit for a temperature sensor. Background Technology

[0002] In the field of temperature measurement, there is an important class of sensors that operate based on the Zener breakdown characteristics of semiconductor PN junctions, such as LM135 and LM235. These Zener diode-type temperature sensors operate with a current range of 0.4mA to 5mA, and their output voltage is proportional to the absolute temperature. During the production and testing of these chips, a fixed resistor is typically used to provide a constant current to the chip. However, different customers have significantly different application scenarios. To ensure that the final product can operate stably and reliably in various practical applications, it is necessary to evaluate the chip's performance at different operating currents. Summary of the Invention

[0003] To address the above issues, a wide-range programmable current excitation test circuit for temperature sensors was designed. This circuit is simple in structure and low in cost, and can automatically and accurately perform rapid testing and evaluation of Zener diode-type temperature sensors with specific current-dependent characteristics across the entire operating current range.

[0004] The purpose of this utility model is achieved as follows: A wide-range programmable current excitation test circuit for a temperature sensor includes chip U2, chip U3, and chip U4. Chip U2 is an instrumentation operational amplifier, chip U3 is a digital-to-analog converter that converts IIC signals to analog current signals, and chip U4 is a Zener diode-type temperature sensor. Pins 1 and 2 of chip U3 are IIC communication interfaces, connected to the host's SCL and SDA buses respectively, and connected to a 3.3V power supply via pull-up resistors R8 and R7. Pin 4 of chip U3 is connected to a 10V power supply for power. Pin 5 of chip U3 is connected to GND, and pin 8 is grounded via capacitor C9. Pin 7 of chip U3 is an analog current output, connected to the base of transistor Q1, and also connected to GND via resistor R1 and capacitor C7. The collector of transistor Q1 is connected to a 10V power supply, and its emitter is connected to GND via resistor R3, resistor R6, and chip U4. One end of C12 is connected between resistors R3 and R6, and the other end is connected to GND. Pin 2 of chip U4 is connected to the host's ADC1. Zener diode D1 is connected to both ends of chip U4. The two ends of resistor R3 are connected to pins 2 and 3 of chip U2 through a low-pass RC network consisting of resistors R2 and R4, capacitors C6, C8, and C11. Pins 7 and 4 of chip U2 are connected to +10V and -10V power supplies, respectively. Pin 5 of chip U2 is grounded. Pin 6 is connected to pin 6 of chip U3 after passing through a low-pass filter circuit consisting of resistor R5 and capacitor C10.

[0005] Compared with the prior art, the beneficial effects of this utility model are: This invention relates to a wide-range programmable current excitation test circuit for a temperature sensor. Through programmable current control, the chip can be automatically and quickly tested and evaluated across its entire operating current range. This allows production testing to cover diverse application scenarios for different customers, ensuring that the chip operates stably within a current range of 0.4mA to 5mA, greatly improving the applicability and reliability of the final product. Attached Figure Description

[0006] Figure 1 This is a circuit diagram of a wide-range programmable current excitation test circuit for a temperature sensor according to the present invention.

[0007] Among them: chip U2, chip U3, chip U4, pull-up resistor R8, pull-up resistor R7, transistor Q1, capacitor C9, resistor R3, resistor R6, capacitor C12, Zener diode D1, resistor R2, resistor R4, capacitor C6, capacitor C8, capacitor C11, resistor R5, capacitor C10. Detailed Implementation

[0008] See Figure 1 This utility model relates to a wide-range programmable current excitation test circuit for a temperature sensor, comprising chips U2, U3, and U4. Chip U2 is an instrumentation operational amplifier, model AD620; chip U3 is a digital-to-analog converter (DAC) that converts IIC signals to analog current signals, model GP8212S; and chip U4 is a Zener diode-type temperature sensor, model LM135.

[0009] Pins 1 and 2 of chip U3 are IIC communication interfaces, connected to the host's SCL and SDA buses respectively, and connected to a 3.3V power supply via pull-up resistors R8 and R7. Pin 4 of chip U3 is connected to a 10V power supply for power supply, pin 5 of chip U3 is connected to GND, pin 8 is grounded via capacitor C9, and pin 7 of chip U3 is an analog current output, connected to the base of transistor Q1, and also connected to GND via resistor R1 and capacitor C7.

[0010] The collector of transistor Q1 is connected to a 10V power supply. Its emitter is connected to resistors R3 and R6 and chip U4 to GND. One end of capacitor C12 is connected between resistors R3 and R6, and the other end is connected to GND, which serves as a filter. Pin 2 of chip U4 is connected to the host's ADC1. The host calculates the temperature of chip U4 by acquiring the voltage. Zener diode D1 is connected across chip U4 to prevent the host from being damaged by excessive voltage at ADC1 when chip U4 is disconnected. Resistor R3 is the emitter current sampling resistor in this circuit. The two ends of resistor R3 are connected to pins 2 and 3 of chip U2 through a low-pass RC network consisting of resistors R2 and R4, capacitors C6, C8, and C11. Pins 7 and 4 of chip U2 are connected to +10V and -10V power supplies, respectively. Pin 5 of chip U2 is grounded, and pin 6 is connected to pin 6 of chip U3 after passing through a low-pass filter circuit consisting of resistor R5 and capacitor C10. At the same time, the host acquires the voltage at this point through ADC2 to determine the actual current flowing through chip U4.

[0011] The specific implementation method of the wide-range programmable current excitation test circuit for a temperature sensor of this utility model is as follows: The host writes data to chip U3 via the IIC interface. Chip U3 linearly converts the data into an analog current output, which in turn controls the collector current of transistor Q1. The current flowing through chip U4 is given by the following formula: I = 2.5V / R3 * (DATA / 0x7FFF), where resistor R3 is the sampling resistor. Pins 1 and 8 of chip U2 are left floating, i.e., the gain is 1. Their function is to convert the differential voltage across resistor R3 into a single-ended signal. Chip U3 achieves closed-loop current output by performing feedback sampling through the FB pin.

[0012] The operating current range of chip U4 is 0.4mA to 5mA. With resistor R3 selected as 390 ohms, the maximum current I can be calculated from the formula to be 6.4mA, which can cover the operating current range of U4.

[0013] The host computer controls the current flowing into chip U4 by writing different data to chip U3, achieving full coverage testing of the operating current range. It uses ADC2 to collect the voltage at the feedback point to determine if the current change is correct, and ADC1 to collect the voltage of chip U4 to evaluate its operation under different currents. A Zener diode D1 ensures that the voltage at ADC1 will not be too high and damage the host computer when chip U4 is disconnected.

Claims

1. A wide-range programmable current excitation test circuit for a temperature sensor, characterized in that, The system includes chips U2, U3, and U4. Chip U2 is an operational amplifier for instrumentation; chip U3 is a digital-to-analog converter that converts IIC signals to analog current signals; and chip U4 is a Zener diode-type temperature sensor. Pins 1 and 2 of chip U3 are IIC communication interfaces, connected to the host's SCL and SDA buses respectively, and connected to a 3.3V power supply via pull-up resistors R8 and R7. Pin 4 of chip U3 is connected to a 10V power supply for power supply. Pin 5 of chip U3 is connected to GND, and pin 8 is grounded via capacitor C9. Pin 7 of chip U3 is an analog current output, connected to the base of transistor Q1, and also connected to GND via resistor R1 and capacitor C7. The collector of transistor Q1 is connected to... A 10V power supply is connected to resistors R3 and R6, and then to chip U4 and GND. One end of capacitor C12 is connected between resistors R3 and R6, and the other end is connected to GND. Pin 2 of chip U4 is connected to the host's ADC1. Zener diode D1 is connected to both ends of chip U4. The two ends of resistor R3 are connected to pins 2 and 3 of chip U2 through a low-pass RC network consisting of resistors R2 and R4, capacitors C6, C8, and C11. Pins 7 and 4 of chip U2 are connected to +10V and -10V power supplies, respectively. Pin 5 of chip U2 is grounded. Pin 6 is connected to pin 6 of chip U3 after passing through a low-pass filter circuit consisting of resistor R5 and capacitor C10.

2. The wide-range programmable current excitation test circuit for a temperature sensor according to claim 1, characterized in that, Chip U2 is model AD620, chip U3 is model GP8212S, and chip U4 is model LM135.

3. The wide-range programmable current excitation test circuit for a temperature sensor according to claim 1, characterized in that, The resistor R3 is the emitter current sampling resistor.

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