Hi,
I am following up on the question about troubleshooting the AD7771 ( Troubleshooting AD7771 ) with a new post, as I am not sure if the previous post is still considered active.
I have made a new PCB with a new AD7771 chip with the same design as in the previous post (except for a RC filter between refout and REF1+/REF2+).
I am still encountering unexpected signals and quality when reading conversions through SPI. The input signal is a clean sinewave from the DAC of the same microcontroller as is used to read from the ADC (ESP32). Please see some examples below for signals read using different configuration options:

Above: Internal reference with low power mode

Above: External reference (Vdd) with powermode=1

Above: Internal reference with powermode=1

Above: With both lower signal frequency and sampling rate

Above: Internal reference in low power mode (different signal range and amplitude from the example above).
Other details that might be of relevance:
When selecting external reference, the Refout voltage is 2.0 V when in low power mode, and drops to 920 mV when in high resolution mode. With internal reference selected (ADC_MUX_CFG = 0b01000000), the voltage is 2.7V.
Reading the error registers typically provides this output:
GENERRREG1:0
GENERRREG2:0
ERR_STAT_REG1:111111
ERR_STAT_REG2:100111
ERR_STAT_REG3:111111
CH0 status err:10000
CH0CH1 dsp err:1
FORMAT0 and FORMAT1 are high (connected to Vdd).
Do you have any suggestions on how to troubleshoot to find the source of error?
Thanks,
Chritron






