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DAC81408: REFGND and GND potential

Hiroaki Yuyama TED
Expert 1400 points
Part Number: DAC81408

Dear, support Team.

I have a question about the potential of the REFGND and GND pins of the DAC81408.
Which is the reference potential of the analog output terminal, REF GND or GND?
The background of my question is that the DUT connected to the analog output of the DAC81408 is far away and I want to sense the GND potential of the DUT and the DAC81408 to the same potential.

Best Regards,
Hiroaki Yuyama

  • 0
    TI__Mastermind 28828 points

    Hi Yuyama-san,

    All circuitry is referenced to the GND pin. This includes the analog output and digital. Only the reference uses the REF GND pin. 

    The applications section of the datasheet does suggest a circuit to compensate for the ground potential variance on the DUT but applying an offset to the reference via the REF and REFGND inputs. 

    Best,

    Katlynne Jones

  • 0 in reply to Katlynne Jones
    Expert 1400 points

    Hi Jones-san,
    Thank you for your reply.

    I connect REF GND and DUT GND and match the DUT GND potential to REF and REF GND in the application example in Figure 67 of the datasheet.
    I keep the potential of REF GND from 0V to +0.6V.

    Best Regards,
    Hiroaki Yuyama

  • 0 in reply to Hiroaki Yuyama TED
    TI__Mastermind 28828 points

    Hi Yuyama-san,

    In figure 67 it looks like DUT GND is connected to the U1B to set the offset on REFGND with an additional 300mV offset applied to ensure REF GND is never negative. This circuit is just a suggestion, you can also accomplish the same offset by sensing the DUT GND and applying the offset by adjusting the DAC code. 

    If you are applying an analog offset to REF/REFGND then it is ok to keep REF GND from 0V to +0.6V with respect to GND. The absolute maximum ratings mandate that REFGND can be up to +0.9V above GND. 

    Best,

    Katlynne Jones