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

Parents
  • 0
    •  Analog Employees 
    on Sep 6, 2016 5:58 PM over 4 years ago

    Hello,

    First, is the SER/nPAR signal set high or low?  If it's high, as you stated above, the part would actually be set in serial mode and many of the data out pins would actually be set as configuration pins for the serial interface.  I don't think this would solve the reference problem, but I wanted to make sure this wasn't a typo.

    Second, are you sure it's the reference that's not working or is it the reference buffer?  I think it's worth probing the REFBUFIN pin to see if it's also 0.3 V or if it's correctly sitting at 2.5 V.  Also, is AVDD at 5 V?  If the REFBUFIN pin is sitting at 2.5 V but REF is 0.3 V then that means there's something wrong with the reference buffer circuitry.

    Also, what do you mean by "inspections?"  Did these include continuity tests, etc. to ensure that the reference pins aren't being loaded down by something?

    Let's start with that for now.  Hopefully your measurements will give us more insight into the problem.

    -Tyler

Reply
  • 0
    •  Analog Employees 
    on Sep 6, 2016 5:58 PM over 4 years ago

    Hello,

    First, is the SER/nPAR signal set high or low?  If it's high, as you stated above, the part would actually be set in serial mode and many of the data out pins would actually be set as configuration pins for the serial interface.  I don't think this would solve the reference problem, but I wanted to make sure this wasn't a typo.

    Second, are you sure it's the reference that's not working or is it the reference buffer?  I think it's worth probing the REFBUFIN pin to see if it's also 0.3 V or if it's correctly sitting at 2.5 V.  Also, is AVDD at 5 V?  If the REFBUFIN pin is sitting at 2.5 V but REF is 0.3 V then that means there's something wrong with the reference buffer circuitry.

    Also, what do you mean by "inspections?"  Did these include continuity tests, etc. to ensure that the reference pins aren't being loaded down by something?

    Let's start with that for now.  Hopefully your measurements will give us more insight into the problem.

    -Tyler

Children
No Data