It sounds like the devices are being damaged at some point during operation. I would suggest doing a continuity test on your board, just to make sure there are no issues there. Is it possible that the device is being exposed to higher voltage than rated for, or ESD exposure. The device does not have power up recommendation, since the AVDD and the DVDD can be independt from each other. it is good practice though to bring up AVDD before DVDD, but bring them up together is just as well. The reference is also independent from AVDD, but it is also good practice that AVDD come up first, or both come up togther. Do you have new parts that are not damaged? Perhaps one can be used to evalaute step by step your procress to see if/when the device is damaged. Regards Cynthia
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