A problem about the internal Vref Of AD7667

Hello!

I am now using an AD7667  conversion chip, and I use  the internal reference voltage, the parallel model, but my output has been FF7F, through inspection , I found that the internal reference voltage on the pin of REF is about 0.3V, this means there is something wrong with the internal reference voltage. But my PD, PDREF PDBUF is low, SER/PAR set to high (that is in parallel model), using the model of IMPULSE . 

And after many inspections ,I am sure the circuit ,pin-strap,and the chip of AD7667 are all good.So what's the problem?

Thanks for your help

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    •  Analog Employees 
    on Sep 7, 2016 11:44 PM over 4 years ago

    No need to apologize, there are a lot of settings to keep track of.

    It doesn't make sense that the REFBUFIN pin would be at 0V if PDREF is indeed low.  Were all three of the AD7667 devices tested in the same socket?  Or were they on different boards?  If you have multiple boards, it would be good to know if the error persists between all of them to ensure that it's a design-related error.  One quick sanity check would be to make sure the REFBUFIN pin hasn't shorted to ground somehow.  Can you just do a quick continuity test to make sure this isn't the case?

    Try that and let me know how it goes.

    -Tyler

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  • 0
    •  Analog Employees 
    on Sep 7, 2016 11:44 PM over 4 years ago

    No need to apologize, there are a lot of settings to keep track of.

    It doesn't make sense that the REFBUFIN pin would be at 0V if PDREF is indeed low.  Were all three of the AD7667 devices tested in the same socket?  Or were they on different boards?  If you have multiple boards, it would be good to know if the error persists between all of them to ensure that it's a design-related error.  One quick sanity check would be to make sure the REFBUFIN pin hasn't shorted to ground somehow.  Can you just do a quick continuity test to make sure this isn't the case?

    Try that and let me know how it goes.

    -Tyler

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