[FAQ] ADS8681: Solution for detecting input floating on SAR ADCs - ADS8681/ADS8688/ADS8686/ADS8588S

Part Number: ADS8681
Other Parts Discussed in Thread: ADS8699, ADS8685, ADS8665, ADS8661, ADS8689, ADS8691, ADS8675, ADS8695, ADS8671, ADS8684A, ADS8664, ADS8688A, ADS8698, ADS8688AT, ADS8688, ADS8678, ADS8674, ADS8684, ADS8694, ADS8668, ADS8586S, ADS8598S, ADS8588H, ADS8598H, ADS8588S, ADS8578S, ADS8584S

The following cookbook introduces a solution to detect if the analog input is floating on SAR ADCs. 

Circuit for detecting input floating on ADS8681 ADC

Key features:

  • Simple solution for input floating detection.
  • No high bandwidth amplifier required because these ADCs have integrated ADC driver and high input impedance - low cost.
  • Small noise from larger resistance in the resistor divider( >M ohms) because of lower output impedance from the source.

This solution can be used for these ADCs:

  • ADS8691, ADS8695, ADS8699, ADS8681, ADS8685, ADS8689, ADS8671, ADS8675, ADS8661, ADS8665
  • ADS8688,ADS8684,ADS8698,ADS8694,ADS8678,ADS8674,ADS8668,ADS8664,ADS8688A,ADS8684A,ADS8688AT
  • ADS8588S, ADS8586S, ADS8584S, ADS8578S,ADS8598S,ADS8588H,ADS8598H,
  • ADS8686