Precise Current Sensing Circuit for Li-Battery Power Management System

A high precision current sense circuit was designed in a 0.18μm BCD IC process and employed in a battery management chip. The influence of offset voltage on current acquisition accuracy is analyzed. The chopper dynamic regulation technology is used to reduce the offset voltage of the amplifier, and the instrumentation amplifier is designed to achieve high precision with a lower detection voltage. The circuit was used in a battery management chip and taped out. The chip test results show that the measurement error of the ADC is less than ±300μV when the input voltage is in the range of −10∼10mV, and the measurement error is less than ± 620μV while the input voltage is in the range of−125∼125mV.