Problem with external VREF AD9629

Hi all,

I have design a board using an ADC AD9629, combined with a differential amplifier ADA4940.
It works fine in normal mode. In normal mode I m measuring single pulses from 0V to 6V to VIN without any issue at 10Msps.
I have used an external reference ADR130BUJZ, in order to compensate the temperature variation of my system.

I have an additionnal DAC (MAX5815) which goes to VIN.  This DAC apply a DC signal to VIN. With this DAC, I can create a lookup table (in my software) to compensate the gain error.

However, am seeing something odd: Whenever i change the DAC value with the ADC clock ON, my external VREF goes from 1V to 0V. Then the Adc is blocked, I have got to unplug my board.

What can create this issue?

AD9629_.pdf
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  • 0
    •  Analog Employees 
    on Jun 18, 2018 11:19 PM

    Hi CrazyFrog,

    Sorry, I too do not know what is happening.

    Is VREF_ADC right at 0V or is it a little above 0V? Does it seem like the ADR130 is trying to drive 1V.

    Another way to ask, does it seem like the ADR130 is off, or does it seem like the load somehow becomes too great for ADR130 to drive?

    Do you have a way of checking the input and output current of ADR130?

    Doug

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  • 0
    •  Analog Employees 
    on Jun 18, 2018 11:19 PM

    Hi CrazyFrog,

    Sorry, I too do not know what is happening.

    Is VREF_ADC right at 0V or is it a little above 0V? Does it seem like the ADR130 is trying to drive 1V.

    Another way to ask, does it seem like the ADR130 is off, or does it seem like the load somehow becomes too great for ADR130 to drive?

    Do you have a way of checking the input and output current of ADR130?

    Doug

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