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Problems with AD7091

Question asked by mikhail.russkih on Jun 14, 2018
Latest reply on Jun 21, 2018 by jcolao

Good day! I have several questions about AD7091.

 

1) How to make a software reset correctly? We are thinking that documentation is written not so accurate in some points.

 

2) What exactly will be with AD7091 if we won’t do software reset?

 

3) Additionally, it is necessary to clarify the operation of the SPI in the program reset mode. We use SPI mode 0 (CPOL = 0, CPHA = 0). Is it OK? Or polarity of SCK should be CPOL = 1 (as in the figure)? Accordingly what phase of CPHA should be?

 

4) We observed the following situation. We use the AD7091 for the analog input, when specifying the current at the input, the ADC chip gave out the code: at 4mA = BA4_hex, at 12мА= 684_hex, at 20мА=165_hex (when the failure occurred), then after a short time after the power reset AD7091 gave out the code 4mA = 290_hex, 12mA = 7B0_hex, 20mA = CD0_hex. It is necessary to clarify whether this is possible, and what will happen if we do not do the correct software reset?

 

 

Additionally, we have oscillograms how we make software reset: yellow CONVST, blue CS, pink SDO, green SCLK.

Also we have a video with failure.

Thank you in advance for your response!

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