Tool/software:
1.When testing the ADS1299, I found that when the ADS1299 did not let PWDN and RESET pins go high, the AVSS was -2.49V, but after turning on PWDN and RESET, the AVSS dropped to -2.2~2.3V, so what could be the reason for this?
2.Is it necessary to add a 10K resistor between PWDN and VCC, and what is the purpose of that resistor?
3.When using the new ADS1299, vcap1 to gnd is the normal value -1.3V, but vcap3 to gnd will be floating value, about 0.4~1V, not long after the ADS1299 is bad, vcap1 to gnd will become AVSS, what may be the reason for this?
Fig1.-2.5V sch
Fig2. ads1299 sch
Fig3.PWDN、reset connect
Fig4. PCB (The white line is the -2.5V line.only connect ADS1299)