ADS1158: DRDYZ asserted without START

Chris Chan1

Part Number: ADS1158

I have an older design with ADS1158, no issue. We moved the same design to an external board and observed and extra DRDYZ. My question is what will cause DRDYZ asserted by itself without a START. I didn't send a pulse convert command.

I have attached two captures below, Never mind about the CS2 on NEW_DESIGN, it was not connected.

Thanks

Chris

OLD_DESIGN

NEW_DESIGN

over 3 years ago

0 Bryan Lizon86 over 3 years ago

TI__Mastermind 35141 points

Hi Chris,

The images you provided did not appear in your last post. Can you try again? Usually I save the images to the hard drive then attach them to the post.

-Bryan

0 Chris Chan1 over 3 years ago in reply to Bryan Lizon86

Prodigy 20 points

HI Brain,

Image attached.

TI_ADC.docxThanks

Chris

0 Bryan Lizon86 over 3 years ago in reply to Chris Chan1

TI__Mastermind 35141 points

Hi Chris,

I see it now, there is an additional DRDY transition (high to low) in the second image, with no activity on DIN or START.

Can you confirm that there is no noise on the START pin line, or any other communication line for that matter? The logic analyzer might not be able to see it, but you can look at your digital communication lines on an oscilloscope as well to make sure you have clean signals. Perhaps it is the case that the ADC is seeing noise spikes.

What specifically is different between the old board and the new board?

-Bryan

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ADS1158: DRDYZ asserted without START