I had made my own PCB with ADAS1000 on board, schematic as below. I believe the schematic is exactly the same as the evaluation board of ADAS1000 (ADAS1000SDZ).
I had made total 6 ADAS1000 PCB boards, but found output DC level of 4 of the boards is higher then the two others, see below :
(left : LL/RA/RL untouched, middle : put fingers on LL/RA/RL, right : then remove fingers from LL/RA/RL)
- the four boards with higher DC level : DC level is about 2.6x10^6 before/during/after putting fingers on LL/RA/RL.
- the two boards with lower DC level : DC level is about 190 before finger touching, about 2.6x10^6 during finger touching, and about 1.8x10^4 after finger touching.
In the previous figures, SNR is good(the middle figures) so DC level drifting is not a problem to me, but when signal is weak and SNR is low, it will be difficult to distinguish whether fingers are placed on leads or not, because middle figure will be similar with the right figure. Or, I will not be able to confirm if fingers were touched well on leads or not during finger touching.
Any suggestions on this ? Below is my register setting for your reference, thanks.
|FF 0002e8||// 1000 samples|
|01 000001||// apply SWRST|
|05 e07002||// LA/LL/RA contribute to RLD common voltage, necessary for DC lead-off detection|
|01 f800ae||// ECGCTL, in digital lead mode|
|0b 000000||// 40Hz LPF|
|0a BFD600||// enable lead II, RESPMEG and LOFF|
|03 000079||// EXT_RESP_LL, external respiration path, amplitude/1, 56 kHz|
|02 000015||// enable only DC lead off detection, 50nA current|