8.4.2.4 Low V_SENSE Case 2: V_SENSE< 20 mV, 0 V ≤ V_CM ≤ V_S

This region of operation is the least accurate for the INA270 family. To achieve the wide input common-mode voltage range, these devices use two op amp front ends in parallel. One op amp front end operates in the positive input common-mode voltage range, and the other in the negative input region. For this case, neither of these two internal amplifiers dominates and overall loop gain is very low. Within this region, V_OUT approaches voltages close to linear operation levels for Normal Case 2.

This deviation from linear operation becomes greatest the closer V_SENSE approaches 0 V. Within this region, when V_SENSE approaches 20 mV, device operation is closer to that described by Normal Case 2. Figure 18 shows this behavior for the INA271. The V_OUT maximum peak for this case is determined by maintaining a constant V_S, setting V_SENSE = 0 mV, and sweeping V_CM from 0 V to V_S. The exact V_CM at which V_OUT peaks during this case varies from device to device. The maximum peak voltage for the INA270 is 0.28 V; for the INA271, the maximum peak voltage is 0.4 V.

Figure 18. Example for Low V_SENSE Case 2 (INA271, Gain = 20)