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DAC8803EVM: Output Verification

Luke Abela
Prodigy 70 points
Part Number: DAC8803EVM
Other Parts Discussed in Thread: OPA227, REF102

I am currently working with the DAC8803EVM and have managed to obtain an output which varies with my input, whoever I have my doubts as to whether this is correct. Could anyone kindly send images of the output of the DAC8803EVM (with no additional filtering) with input words all 0s, all 1s, and alternating 1s and 0s for comparison`s sake. Thank you

  • 0
    TI__Guru 52663 points

    Hi Luke,

    Could you share the configuration you are using for the EVM (IE the jumper positions and supply values)?

    Thanks,
    Paul

  • 0 in reply to Paul_Frost
    Prodigy 70 points

    Hi Paul,

    Thanks for the quick reply. Im using +-12V as well as +-5V. With reference to the jumpers, My switches are set for bipolar outputs, with regards to the reference: W5, W6, W7, W8 are all shorted to positive reference. W10 connectes the REF102 to the opa227.

    I am referencing page 7 of this document:

    Regards,

    Luke

  • 0 in reply to Luke Abela
    TI__Guru 52663 points

    Hi Luke,

    Using a +10V reference with the bipolar output configuration you should have an output range of approximately -10V to 10V.

    The means that your output function should be:

    Vout(D) = ((D/0x2000)-1) × 10V

    For all 0's (0x0000), you will have Vout(0x0000)= ((0x0000/0x2000)-1)×10V = -10V

    For all 1;s (0x3FFF), you will have Vout(0x3FFF) = ((0x3FFF/0x2000)-1)×10V = 9.998V

    For 3/4 scale, or 0x2FFF, you will have Vout(0x2FFF) = ((0x2FFF/0x2000)-1)×10V = 4.998V

    What are you measuring?

    Thanks,

    Paul

  • 0 in reply to Paul_Frost
    Prodigy 70 points

    Hi Paul,

    Thanks for the insight. More than the raw numbers, I was hoping to be provided with something along the lines of oscilloscope screenshots of the Dac's output. I've written an SPI code on my FPGA, and am looking to verify it. I'm asking as I'm not sure what is the level of filtering including within the DAC itself. Thanks

    Regards,

    Luke

  • 0 in reply to Luke Abela
    TI__Guru 52663 points

    Hi Luke,

    I doubt I will be able to capture scope shots of this for some time.  Do you have a specific concern? Do you see excessive noise?  There is no noise filtering built into the device or the output stage.  Are you seeing digital crosstalk?  

    Thanks,

    Paul

  • 0 in reply to Paul_Frost
    Prodigy 70 points

    Hi Paul,

    Sorry for not getting back to you sooner. I`m currently seeing my output voltage vary between 0 and 10V as expected. I managed to find my issue. Thanks for the help!

    Regards,

    Luke