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DAC80504: LDAC

Jorge Vega
Intellectual 300 points
Part Number: DAC80504

Hello, 

1. I have configured DAC80504 with LDAC tied to VIO permanently and would like to understand the implication of this connection.?

2. The EVM for DAC80504 shows LDAC with option to ground, send VIO or send a GPIO command, is this correct?

The functionality that I want is for the outputs to update independent of each other.  

Thanks for your help.

Jorge Vega

  • 0
    TI__Genius 14220 points

    Hi Jorge,

    Thank you for your query. The LDAC is an active low input. Hence, it should be pulled-up HIGH by default so that you can drive it LOW whenever you want to change the DAC outputs. This is called synchronous update. In case you want to update the DAC outputs as soon as you write to the register, pull this pin LOW so that the input is ignored.

    Hope that answers your question.

    Regards,

    Uttam Sahu

    Applications Engineer, Precision DAC

  • 0 in reply to Uttam Sahu
    Intellectual 300 points

    Thanks for quick reply,

    Let me reflect back what you explained to me.

    1. LDAC can NEVER be tied to VIO

    2.LDAC can be set to GND and by doing so, all outpusts will update simultaneously all the time.

    3.LDAC can be tied to a GPIO with a pull up to VIO so that it updates on command.

    Are these statements accurate?

  • 0 in reply to Jorge Vega
    TI__Genius 14220 points

    Please see my response below:

    1. The LDAC pin can be tied to VIO. It will be ignored if the DACx-SYNC-EN bits in the SYNC register  (Table-11 of the datasheet) are set to 0. 

    2. Tie LDAC to GND when you want the DAC output to update after a write to the corresponding DAC channel. Note that all channels won't update simultaneously. Once you tie the LDAC low, there will be no difference between the synchronous and asynchronous modes. tying LDAC always low means ignoring the pin

    3. For synchronous updates drive the LDAC pin separately. It is better to pull this pin HIGH so that it is not floating during power-up. By driving this pin, you can either update every channel separately after corresponding write commands or update all channels simultaneously once all channels are written to

    Hope that clarifies your doubts.

    Regards,

    Uttam

  • 0 in reply to Uttam Sahu
    Intellectual 300 points

    Many Thanks Uttam.  This points me in the right direction.