Hello,
We are using the ADS1292 chip for an EMG acquisition application. On our most recent hardware revision, we encountered a problem that the VREFP pin on the chip is not generating 2.42V voltage. On a earlier design, this wasn't an issue. Here are the debug steps we did:
1. Inspected solder quality of the DUT.
2. Flashed the DUT so that streaming data from the ADS1292 chip is enabled, the PDB_REFBUF bit in CONFIG2 register is set to 1.
2. Probed DVDD(1.8V) and AVDD(3V) and confirmed that they are at the nominal values. We are using single ended supply for the analog voltage rails (AVDD=3V and AVSS = 0V).
3. Checked that VCAP1 and VCAP2 are at nominal values. VCAP=1.2V, VCAP2 was about 4.9V.
4. Measured the voltage at VREFP and it was at 0V.
5. Swapped out the ADS1292 chip with another ADS1292 from a different batch, still no VREFP output.
6. Queried CONFIG2 register and confirmed that the PDB_REFBUF is set to 1.
I have also tried putting on the same code on an older design, and VREFP was generating 2.42V as expected.
I was wondering what your thoughts are on why the VREFP is not generating 2.42V? Attached below is the schematic for the ADS1292 chip.
Thank you in advance for your help!
Grant
