Part Number: ADS127L01
Other Parts Discussed in Thread: ADS1672
I recently migrated a design from the ADS1672 to the ADS127L01. I wanted to bring up an issue I had that might save someone else some trouble. On the ADS1672, there is a pin called "VCM" which the data sheet says is a weakly buffered version of AVDD/2, and there is a sentence in the data sheet suggesting that this can be used as a common mode reference voltage for your external differential driver IC, but to be careful not to overload it.
The ADS127L01 does not have a similar pin labeled VCM, but the description for CAP1 says it is the common mode signal for the main modulator. It appears that this doesn't mean what I thought it meant, as attempting to use this pin to bias the differential op amp makes me think that the voltage on CAP1 is not AVDD/2 but the measured common mode voltage of the inputs AINP and AINN. Obviously, using this voltage to set itself is a bad idea deserving honorable mention in the pantheon of bad ideas.
Had I not migrated the design from the ADS1672, I wouldn't have made this error. I suggest either giving more information about the exact function of CAP1, or less information and "Do not connect anything to this pin besides a 1 uF capacitor to ground". In other words, the data sheet currently has the exact wrong amount of information in its current revision.
