Hi exparts,
ADS7863A supports single-ended/Pseude-differential input. Can this device be used as single-ended ADC if CHAx- is connected to GND? If it is OK, what things we have to care? Could you also tell me the difference between ADS7863A and Pseudo-Differential/Single-ended input ADC like ADS7948?
Regards,
Hiromu
Hello Hiromu-san,
The ADS7863A can be used in a Differential or Pseudo-Differential configuration. This device is primarily (internally) a Differential SAR ADC, which typically has an input common mode requirement that has to be met. The way this can work in Pseudo-Differential mode is if the CHx0- remains at VREF (2.5V) so the input common mode requirement can be met.
The ADS7958 on the other hand can be used in either Pseudo-Differential or Single-ended configuration. This ADC is primarily a Single-ended device but the AINxN pins have a wider input range (±0.2V) than typical for an SE device so it it able to be used in Pseudo-Differential mode if the sensor or source has a small DC offset.
The difference between these two devices is the input requirements/capabilities. Because the ADS7863A is a differential ADC the input range is ±VREF but the Absolute input range is 0V to AVDD (Max 5.5V). For this to work, the input common mode (AINP-AINM)/2 = VREF.
The ADS7958 has a unipolar input range that matches the absolute input range, making it easier for unipolar single ended signals. The added benefit this device has is that the AINM/N pin does not have to be hard tied to GND, but has a small range outside 0V that it can accept allowing it to work in a pseudo-differential mode.
Best regards,
Yolanda
