SDAA088 September   2025 AMC0100R , AMC0311R , AMC0311R-Q1 , AMC0330D , AMC0330R , AMC0330R-Q1 , AMC0330S , AMC0336

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Pairing Ratiometric Output Isolation Amplifier With ADC
    1. 2.1 Test Setup
    2. 2.2 REFIN Voltage Tracking
    3. 2.3 Ratiometric Configuration Noise Rejection
    4. 2.4 Spurious-Free Dynamic Range
    5. 2.5 Transient Response of REFIN to VOUT
    6. 2.6 Transfer Function of REFIN to VOUT
  6. 3Summary
  7. 4References

2 Pairing Ratiometric Output Isolation Amplifier With ADC

Isolated amplifiers typically interface with single-ended ADCs. The ADC input range corresponds to the reference voltage (VREF) that is either generated internally, or externally.

For the ratiometric output device, if REFIN and VREF share the same voltage, the absolute voltage is not important as both ends adjust the gain automatically and track each other. This eliminates the need for a precise voltage reference, automatically compensates for long term drift and low-frequency ripple. Of course, the effect is limited to certain voltage and frequency range. Nevertheless, this configuration effectively suppresses low frequency ripple and reference voltage deviation. Next chapters highlight in-system rejection performance of the signal chain featuring AMC0330R, paired with TMS320F28P650 microcontroller with 16b successive approximation register (SAR) ADC.