SBAA551 June 2022 ADS8661 , ADS8665 , ADS8671 , ADS8675 , ADS8681 , ADS8685 , ADS8689 , ADS8691 , ADS8695 , ADS8699 , INA823 , INA826 , LM317L , LM337L , MUX509 , TPS2661 , TPS560430
The common-mode rejection ratio (CMRR) is the ability to suppress unwanted common-mode signals superimposed to the differential signal. A CMRR test is performed by comparing the output codes for a 1-V differential voltage with and without a VCM signal applied. The following table shows that with no VCM signal, the system had an output code deviation of –1 code. Comparatively, the design showed a deviation of –4 to +3 codes with –11.5-V and +11.5-V VCM, resulting in a measured VCM rejection of > 81 dB.
| VCM | Input | VRANGE | Measured | Expected | Δcode |
|---|---|---|---|---|---|
| –11.5 V | 1 V | ±2.56 V | 45563 | 45568 | –5 |
| 0 V | 1 V | ±2.56 V | 45567 | 45568 | –1 |
| +11.5 V | 1 V | ±2.56 V | 45570 | 45568 | +2 |