Figure 2-2 highlights the current measurement portion of the circuit. This function is based on the INA241 high-precision current measurement amplifier [2]. The device's extremely low (8µV, max) input offset voltage and (100nV/⁰C, max) drift enable very low value shunt resistors. The 100µΩ shunt resistor shown in the example schematic produces a voltage drop of 5mV at 50A of output current and 10mV at 100A (200% rated capacity). The "A5" variant of the INA241 has a fixed voltage gain of 200V/V. Therefore, at 200% rated output current (100A) the INA241A5 produces an output voltage of 2V.

Both reference pins on the INA241A5 are shown tied to ground such that at 0A output current, the INA241A5 output tries to reach 0V. However, the minimum output voltage of the INA241A5 is specified at 20mV max which translates to a minimum measurable current of 1A for a 100µΩ shunt. Above the minimum output voltage, error in the measurement comes predominantly from the INA241A5's maximum input offset voltage, 8µV. This offset voltage equates to 80mA of error in the current measurement, or 1.6% error at 10% rated output, which is well within the tolerance guidelines of the M-CRPS specification. An optional low-pass filter circuit consisting of R_FILT and C_FILT is shown in the schematic if bandwidth limiting is desired. The unfiltered ˗3dB bandwidth of the INA241A5 is 1.1MHz which is more than capable of achieving the <20µs signal delay requirement.