Hello,
We use the ADS8568 in one of our designs to monitor 60 Hz signal quality.
We have a signal stability problem at low temperature in our qualification tests.
The problem occurs on at least ONE channel of SOME systems only. It is very repeatable when a system has the problem.
At around -10 to -20 deg C, we see an offset of some ADC counts (32-64) appear on the data....
The duration of the presence of this offset is variable and disappear when the temperature goes back over -10 deg C.
This offset appears instantly, so it's not a question of analog drift.
We have made a subtraction of raw data on channel 1 vs channel 2 to detect this offset.... So, at the same time, problem is present on channel 1 but not on channel 2.
We also have frequency analysis algorithm that detect frequency change (60 Hz) in the application, and it is detected on channel 1.
Here is a quick description of the conditions:
- 60 Hz signal is generated from a quality voltage source (Omicron);
- The same 60 Hz signal is connected to all the channels;
- All channels have the exact same design (Input stage, low pass filter, ...);
- Sampling Rate is low at 7680 Hz;
- Same signal is used on the 4 CONVST pins;
- Configuration Pins: RANGE 4x VREF/ EXTERNAL REFERENCE / HARDWARE MODE / PARALLEL
- All capacitors and other components are as requested by the datasheet and the evaluation module.
- All digital interface timings have been checked.
- We have seen an issue with some BUSY to READ delay on the forum. We applied a larger delay with no success... (As requested by an updated datasheet)
I went thru all the forum posts about the ADS8568 and the one named "ADS8568: Missing codes when device is cooled" looks a bit similar to our problem,
Can you help us with this problem ?
