Dear product line engineer.
my customer use ADS1299-4 in their application, but they find that internal ADC of ADS1299-4 sometimes will be over-ranged if they configure ADS1299-4 as below.
1. internal lead-off current equal:6nA.
2.enable lead-off function.
3.configure gain of internal PGA=12.
please figure out the potential root cause and help to check the schematic and register configure is correct? the schematic and register configure as below.
thank you very much!
regards,
Bill
Hi Bill,
May I ask for some clarification -
When customer says
"
internal ADC will be over-ranged if they configure ADS1299-4 as below.
1. internal lead-off current equal:6nA.
2.enable lead-off function.
3.configure gain of internal PGA=12.
"
A. When they say "over-ranged", Do they mean the ADC value(code, count) saturate to the ADC maximum?
If no, what do they mean by "over-ranged"?
If yes to A, what is their AVDD, AVSS, DVDD and VREF? Please note that the Full-Scale range depend on the VREF and gain settings -
If yes to A, do they observe this when the electrode is ON or OFF? or doesn't matter?
If yes to A, what input signals do they inject/input to the channels? and what are the input signal range?
If yes to A, does this happen to all the channels they configured as above? or only to certain particular channels?
If yes to A, PGA=12 is the 2nd highest gain, will the lower PGA gain e.g. PGA=8 meet their need?
If yes to A, Did they try PGA=24(highest gain) and did they see same issue?
If yes to A, have they tried the same configuration and setup using the ADS1299EVM? Is the result similar?
Thanks
