AD7770 Error misunderstanding

Hello all.

I found some misunderstand error flages active.

1. We connect ch5 input with 2 DC signal. one is 1V on the positave side and one is 200mV on the negative one. We read the result correct on the output. But when we look on the error register especially CH5_ERR_REG we found bit CH5_ERR_AINM_UV and CH5_ERR_AINP_UV both. They mean AIN5− Undervoltage Error. We also make continues reading and the voltage was fix. We also read the error all the time but still get it.

Attach a picture from the scope. The blue line is the positive input where the pink is the negative one.

Why it set this error?

We also have a question about the filter error. It is written "This detection indicates that the filter output is out of bounds, which represents an output code approximately 20% higher than positive or negative full scale." Does it mean if it get on its input voltage higher then the limit or it is concerning its internal arithmetic that can be over its limit because to much samples . ANd if so what could protect it against it?



adding tags
[edited by: Lluis at 9:01 AM (GMT 0) on 19 Nov 2019]