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DAC60508: Can I simultaneously update all DAC channels on several daisy-chained DACs

David Naviaux
Intellectual 590 points
Part Number: DAC60508


Tool/software:

I have an application that uses 5 daisy-chained DACs (40 total DAC channels).  I would like to update all 40 DAC channels then simultaneously update the outputs of all 40 DACs at the same time.

Is that possible, and if so how do I go about doing that?

Thank you,

David

  • 0
    Intellectual 590 points

    I have never used this DAC before.  Would this work:

    1. Set all DAC channels so that the LDAC trigger is used to update the DAC outputs simultaneously 
    2. Drop CS low
    3. Write DAC 0 of all 5 daisy-chained DACs
    4. Raise CS high
    5. Repeat 2 through 4 for all 8 DAC channels
    6. Drop CS low
    7. Set the LDAC trigger bit on all 5 DACs
    8. Raise CS high

    . 

  • 0 in reply to David Naviaux
    TI__Mastermind 42273 points

    Hi David, 

    Your sequence will work, but the LDAC command will still need to propagate through all of the daisy chained devices. Each set of 8 channels would have a small delay.

    If you used a part with a HW LDAC, you could short all of the LDAC pins together to get all of the outputs of the chained devices to update at the same time. 

    Best,

    Katlynne Jones

  • 0 in reply to Katlynne Jones
    Intellectual 590 points

    Thank you Katlynne,

    I was thinking that the write to the trigger register would not occur until the CS line was raised.  If that is true, since I wouldn't raise the CS line until all 5 DACs in the daisy-chain have had their trigger register updated with the LDAC bit set, wouldn't that mean that the 5 DACs would have all of there 8 channels updated at the same time?

    Thank you,

    Dave

  • +1 in reply to David Naviaux
    TI__Mastermind 42273 points

    Hi David, 

    You are right, the device will not take any action until the CS is raised. With this device, each DAC in the chain will capture the last 24 bits of data before the CS was raised. When you raise the shared CS high, they should all latch the LDAC trigger command at the same time. 

    Best,

    Katlynne Jones

  • 0 in reply to Katlynne Jones
    Intellectual 590 points

    Hi Katlynne,

    Thank for taking the time to help.

    Regards,

    David