As illustrated in Figure 50, the value of VSHUNT is the ground potential for the system load. If the value of VSHUNT is too large, issues may arise when interfacing with systems whose ground potential is actually 0 V. Also, a value of VSHUNT that is too negative may violate the input common-mode voltage of the differential amplifier in addition to potential interfacing issues. Therefore, limiting the voltage across the shunt resistor is important. Equation 6 can be used to calculate the maximum value of RSHUNT.
Given that the maximum shunt voltage is ±25 mV and the load current range is ±2.5 A, the maximum shunt resistance is calculated as shown in Equation 7.
To minimize errors over temperature, select a low-drift shunt resistor. To minimize offset error, select a shunt resistor with the lowest tolerance. For this design, the Y14870R01000B9W resistor is used.