Problem with external VREF AD9629

Hi Doug,

Thanks for your feedback.

Yes, below my configuration with the DAC...

My current work around is to stop running the ADC clock, and then change the DAC value and restart ADC. Then I get the correct value. But I don't understand why, the VREF goes to 0V....

I have made several boards showing the same results.

+5V_ANA is always good.

regards

Hi CrazyFrog,

• To confirm, are you saying that the output of the ADR130 goes to 0V when you change the DAC value, with the ADC clock running?
• If the ADC clock is not running, do you see the same thing happen on VREF? Of course, the ADC will not work without the clock.
• There seems to be some interaction with the DAC and ADR130. Do you have a schematic that includes the DAC?
• When VREF_ADC goes to 0V is +5V_ANA still at 5V?

Thanks,

Doug

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

Found my mistake,

The duty cycle was not at 50%... but about 20%. If I change it to 50% the Vref goes back to 1 V.

Thanks Doug for your input.

Hi CrazyFrog,

Good work! I would never have guessed the problem.

I hope your project goes well.

Doug