Hello,
I am trying to implement DC current lead-off detection in ADS1294, but have some difficulty to understand details related to comparators. I have found nice picture in the sbas459k datasheet, but comparators inputs are not described, therefore I have described them regarding to my understanding and assumed 20% and 80% thresholds like below:
I have found following description in the sbaa196a "Understanding Lead-Off Detection in ECG" application report:
My understanding is as follows:
- when VINP is disconnected, then it is pulled up to AVDD by the DC current source and it's voltage is >80% of VDD. Therefore LOFF_STATP = 0.
- when VINN is disconnected, then it is pulled down to AVSS by the DC current source and it's voltage is <20% of VDD. Therefore LOFF_STATN = 0.
So, voltage at VINP must be <80% of VDD, and voltage at VINN must be >20% of VDD to be detected as connected.
Can anybody confirm if my assumption of comparators inputs description and understaing of the circuit is correct?
Thanks & regards!
Maciej
