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AD7689 SDO stuck low

Question asked by XSC-flr on Mar 16, 2015
Latest reply on Apr 24, 2015 by KarenNE

Hello,

 

On 3 out of 4 boards I have built that use an AD7689 SDO is stuck low from power up even if CNV is high. I used this chip successfully on multiple boards therefore I am pretty confident the circuit is good.

 

I noticed that if VDD ramp is slower than VIO, SDO will go high for a brief period of time (probably until VDD reaches its minimum level). If I increase VDD slew rate then SDO stays low.

 

SCK and DIN are driven high by the SPI master.

 

The chip does not heat and I am pretty sure we did not apply voltage outside the maximum ratings.

 

Are there any known causes to this issue?

 

Thank you

 

Francesco

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