Programmable linear constant current source circuit leakage current type: based on PAC chip GP8102, GP8202

zjqmyron

Programmable linear constant current source circuit leakage current type: based on PAC chip GP8102, GP8202 [Copy link]

PAC chips GP8102 and GP8202 are dedicated programmable linear constant voltage and constant current driver chips. Through the cooperation of peripheral power devices (transistors, MOS), programmable constant voltage or constant current output can be achieved.

There are two programming methods. GP8102 supports PWM programming, that is, the PWM duty cycle changes linearly from 0% to 100%, and the corresponding output value changes linearly from minimum to maximum. GP8202 supports I2C interface programming, that is, the output value changes linearly from minimum to maximum by directly writing data, and GP8202 has built-in EEPROM, which can record the programming value inside the chip, and the set value will not be lost after power failure.

Circuit principle: The operational amplifier inside GP8102 forms a closed loop with the peripheral MOS tube and low-end current sampling circuit. The current sampling circuit is connected in series with the sampling resistor RS, and the voltage VRS across RS is amplified 50 times by the differential operational amplifier LM321 and then fed back to the negative input terminal of the operational amplifier inside GP8102 as VFB, while the positive input terminal of the internal operational amplifier is the output voltage 5V*DPWM of PAC (DPWM is the duty cycle of the input PWM signal). According to the virtual short characteristic of the operational amplifier, VFB is also 5V*DPWM, and the voltage across the sampling resistor VRS=VFB/50=0.1V*DPWM can be obtained, so the output current IOUT=0.1V * DPWM/RS is obtained, and DPWM is the duty cycle of the PWM signal. If RS=0.1Ω is selected, IOUT=1A*DPWM, that is, IOUT can be realized in the range of 0-1A through PWM programming.

If GP8202 is used instead of GP8102, the output current can be controlled through the I2C interface.

Module physical picture

Application connection diagram

GP8102_cn_V1.7.pdf (434.64 KB, downloads: 23)

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GP8202_cn_V2.2.pdf (447.71 KB, downloads: 28)

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This content is originally created by EEWORLD forum user zjqmyron . If you want to reprint or use it for commercial purposes, you must obtain the author's consent and indicate the source

dcexpert

What is the accuracy?

zjqmyron

dcexpert posted on 2020-1-17 14:10 How is the accuracy?

Within 1%

dwwzl

Achieving 0.1% accuracy will go a long way!

zjqmyron

dwwzl posted on 2020-1-18 10:12 A precision of 0.1% will be very useful!

Do you mean 4-20mA?

dwwzl

zjqmyron posted on 2020-1-18 11:01 Do you mean 4-20mA?

Many isolated remote transmission signals including 4-20mA

qingzhu1984

This is good for industrial control.

hanzhen91

dwwzl posted on 2020-1-18 10:12 A precision of 0.1% will be very useful!

We are working hard on this and will launch products with higher precision later.