Hi Team,
My customer Advantech is working on a Sound/Vibration DAQ, they are using PCM4220, it's closed to RTM (2015 Q2). Currently they are seeing a strange problem. Here is how to duplicate the issue.
0.Turn on the power and initialize register.
1. Apply voltage to input
2. Use Normal mode 54KS/s and run for a while to capture enough data, then we can obtain a RMS noise value
3. Change to Quad Speed Mode 216 kS/s and run for a while
4. Change back to Normal Mode 54 kS/s and run for a while to capture enough data, this time the RMS noise is different. The noise increase 2~3x than in step.2.
5. problem can be resloved by RESET the device.
What can be the root cause? Is that due to digital filter remains historical data of 216KS/s?
Many thanks for help.
P.S. The project block diagram is attached.
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