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DAC7811EVM: DAC7811EVM communication issue

Dileep D R
Intellectual 620 points
Part Number: DAC7811EVM
Other Parts Discussed in Thread: REF102, DAC7811

Hi,

I am using DAC7811EVM board.

I have given +5V to pin 1 and 10. -5v to pin 2. Pin 5 i have grounded with my interface baord.

When i communicate on spi lines. No voltage change at TP2. I am sending only load and update command (attached is the snap of timing diagram).

Please help in rectifying the issue.

Regards,

Dileep

  • 0
    TI__Mastermind 46290 points
    Dileep,

    What is the reference source in your setup? The on-board REF102?

    The REF102 is a 10V reference and requires at least 11.4V input voltage. According to your setup you are providing only 5V at J3.1, therefore I am not certain of what output voltage you will see from the REF102 (if any at all).
  • 0 in reply to Kevin Duke
    Intellectual 620 points
    Kevin,

    With current setup which i mentioned previously, I am able to measure across W3 jumper +5v and -5v. So with W3 I can choose Vref for DAC7811.

    Will this work ? or What voltages I need to provide at J3 ?

    Regards,
    Dileep
  • 0 in reply to Dileep D R
    TI__Mastermind 46290 points
    Dileep,

    To an extent I must defer to the REF102 datasheet requirements of a 11.4V input voltage for proper operation. However, if you are observing a stable DC voltage(s) across W3 at the input to the DAC, then there is no reason that these shortcomings would impact the behavior of the DAC.

    The SPI frame you have shared looks to contain binary 1000 in the MSBs which is a reserved command for the device assuming D1 is the SDI pin for the DAC. The load and update command should contain 0001 in the MSBs.