Purpose : For sEMG
Condition :
I have prestage for INP(a few filters and amplifiers before ADC)
AVDD : 5V, AVSS : 0V, PGA=1
Single input INP : swing around 2V(limited from 0V to 5V by prestage OPAMP)
1.1 when I use internal reference 4V and connect INN to 0V,
INP swings around 0V? so it loses signal under 0V?
1.2 internal reference 4V but INN to 2V common voltage same as INP,
INP swings around 2V? in theory, range is from -2V ~ 6V but in practice, 0V~5V? or 0V~4V?
Which one is right?
1.3 Vin = INP –INN
At 1.1 Vin = INP -0V = INP and at 1.2 Vin = INP – INN = INP – 2V(AC signal swings around 0V). which one is right?
And in which situation will I get 7FFFFFh code? Over Vref 4V?
2.1 internal reference is 2.4V and INN is connected 2V
What is INP range? Theoretically -0.4 ~ 4.4V but in practice 0~4V? or 0~5V?
And here when INP is over 2.4V, output code is 7FFFFFh?
2.2 When INN is tied to 2.5V and internal reference is 2.4V (AVDD = 5V)
in this condition, from where INP(AC signal, dc offset is 2V and swinging around 2V) swings?
and what is its range?
3.electrode can be connected to ADS1298 directly for sEMG? or it needs signal conditioning?
4. when I don't use pace detection,should I connect TESTP_PACE_OUT1 and TESTN_PACE_OUT2 to AVDD?
5. there are analog ground and digital ground, is it okay to tie togather?
Thanks for answer