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DAC8565: Strange VRef?

FreddieTheRobot
Prodigy 40 points
Part Number: DAC8565

Hello,

I have up a DAC 8565 with a raspberry pi, and am bitbanging the DAC with no issues; however, the output is only at 1/10th of what I am asking of it. 

Here is my schematic:

Is there any issues that you can spot? I am not using any libraries with the rasb pi, and it doesn't seem to be a software issue; I used an O-scope on my VrefH/OUT pin and found that it was only at 250mV, 1/10th of the intended internal voltage reference. I can even hook up an external reference of 3.3V; and on probing each of my channels, full scale output was at 1/10th (330mV). 
Am I doing something wrong? 

Thanks,

JM

  • 0
    Prodigy 40 points
    I have decided to try a second breakout with the same wiring, and I am still getting 1/10th Vref full scale output when using the same wiring set up. This is a pretty good indication to me that the chip itself isn't damaged, if on two tries they both have the same exact problem...
  • 0 in reply to FreddieTheRobot
    TI__Guru 53623 points
    HI Freddie,

    Can you confirm the voltage on the Vrefout pin? Is that 2.5V on power up? And this may sound like a silly question: are you using a 1/10 attenuation scope probe? Sometimes the setting on the scope can be 1/10 when you are using a non-attenuated probe. Maybe confirm with a DMM?

    Thanks,
    Paul