Design of Lithium Battery Voltage Sampling Circuit Based on Digital Domain Calibration

This paper proposes a high-precision voltage sampling circuit for lithium batteries. Voltage sampling is carried out through operational amplifiers. Meanwhile, the operational amplifier offset problem and resistor mismatch problem existing in the operational amplifier sampling are calibrated respectively in the digital domain. By calculating the difference between the actual voltage conversion coefficient and the ideal designed voltage conversion coefficient, the offset is obtained, and the quantized voltage of the ADC is adjusted to achieve the calibration of the voltage conversion coefficient. Sampling and quantification are carried out again based on the adjusted reference voltage to obtain the offset voltage <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{K}$</tex> of the operational amplifier in each channel and complete the calibration. Finally, in the sampling stage, the battery voltage sampled from the analog front end is converted into digital codes and then subjected to corresponding operations with the stored offset voltage <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{K}$</tex> to obtain the final sampling result, which improves the voltage sampling accuracy. Based on the 0.35 um BCD process, this paper simulates the battery voltage sampling circuit. Under typical circumstances, the maximum error of voltage sampling is 1.25 mV.