In a typical BMS, the current through the shunt resistor must be measured in both directions for charging and discharging the battery pack. In an overcurrent or short-circuit condition, the current can be as high as I_{BAT_MAX} = ±5 kA in this example application. Therefore, the maximum voltage drop across the shunt is up to V_SHUNT =
R_SHUNT × I_{BAT_MAX} = 35 μΩ × ±4 kA = ±140 mV.

To measure this shunt voltage, configure channel 1 of the ADS131M04-Q1 for gain = 8, which allows differential voltage measurements of V_IN1 = V_AIN1P – V_AIN1N = ±V_REF / 8 = ±1.2 V / 8 = ±150 mV. The integrated charge pump in the device allows voltage measurements 1.3 V below AGND while using a unipolar analog power supply. This bipolar voltage measurement capability is important because one side of the shunt is connected to the same GND potential as the AGND pin of the ADS131M04-Q1, which means that the absolute voltage that the device must measure is up to 140 mV below AGND.

To enable fast overcurrent detection within 1 ms while providing high accuracy and resolution, operate the ADS131M04-Q1 at 4 kSPS (OSR = 1024, high-resolution mode) using global-chop mode. Global-chop mode enables measurements with minimal offset error over temperature and time. The conversion time using these settings is 0.754 ms according to Equation 9. The input-referred noise is approximately 2.70 μV_RMS / √2 = 1.91 μV_RMS following the explanations in the Section 7.1 section. Thus, currents as small as 1.91 μV_RMS / 35 μΩ = 55 mA can be resolved. The resolution can be further improved by averaging the conversion results over a longer period of time in the microcontroller that interfaces with the ADS131M04-Q1.