I am trying to use the lead-off functionality on the ADS1291. I am using 3.3V digital supply and a +/-2.5V bipolar analog supply. I am able to acquire the ECG signal perfectly fine, but I cannot get lead-off detection to work: the LOFF_STAT bits always return zero (leads-on status). My relevant register settings are as follows:
LOFF: 0x10
CONFIG2: 0xE0
LOFF_SENS: 0x03
I am not using pull-up/pull-down resistors on the input lines and the inputs are not ac-coupled. I have a lowpass filter on each input and nothing more. I am using dry stainless steel electrodes. I noticed on the ADS1298, there is an additional setting on the LOFF register to select VLEAD_OFF_EN for resistor or current source mode. This option does not seem to be available on the ADS1291/ADS1292. Is there a reason for this? Is only one of these options possible? It's not clear from the datasheet.
Thank you!