Proper selection of resistors R1, R2, R3 and R4 is critical for meeting the overall accuracy requirements.
Using Equation 6, the offset term, VOUT-OS, and the gain term, AOUT, of the differential ADC input are represented by Equation 9 and Equation 10 respectively. The error contributions from the first-order RC filters are ignored.
The tolerance, drift and linearity performance of these resistors is critical to meeting the overall accuracy requirements. In Equation 9, if R1 = R3 and R2 = R4, VOUT-OS = 0 V and therefore, the common-mode voltage, VCM, only contributes to level-shift VSHUNT and does not introduce any error at the differential ADC inputs. High-precision resistors provide better common-mode rejection from VCM.