Part Number: ADS9229
Hello,
We have a hardware design that uses 12x ADS9229 on one PCB. Now we are at the production stage. While testing a production batch, we figured out that one ADS9229 chip might be malfunctioning when sending a digital ramp test pattern. Below are the waveforms comparing a working channel and a non-working channel (ADC21). All the ADCs are working in 1-Lane DDR mode. There is an analog stage before the ADC input, which has an input range of -10V to 10V, to scale down the voltage to +/-3.2V for the ADC input.
I suspect that this issue comes from the ADC itself because this abnormal behavior only happens with the digital ramp mode. When feeding a normal analog sine wave to it, the output data seems normal, see the picture below:
Moreover, if I zoom into the digital ramp waveform:
The difference between the wrong data and the correct data is close to 10V / 2^6 = 0.15625V. To my understanding, this can be explained if one bit in the ADC's internal ramp counter is short-circuited to GND.
Does my suspicion sound reasonable to you? Have you ever seen a similar issue before? Please let me know if you need further information.