Hello!
I am now using an AD7667 conversion chip, and I use the internal reference voltage, the parallel model, but my output has been FF7F, through inspection , I found that the internal reference voltage on the pin of REF is about 0.3V, this means there is something wrong with the internal reference voltage. But my PD, PDREF PDBUF is low, SER/PAR set to high (that is in parallel model), using the model of IMPULSE .
And after many inspections ,I am sure the circuit ,pin-strap，and the chip of AD7667 are all good.So what's the problem?
Thanks for your help