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DAC8734: REFGND different from GND ?

tobias kosub
Prodigy 150 points
Part Number: DAC8734
Other Parts Discussed in Thread: ADS1278, , DAC81408

Hi,

I want to use AVDD/AVSS = +/- 15 V, AGND = SGND = GND = 0V

REFGND = 0.25 V, REF = 5.25 V gain of 4 config.

This is within the maximum ratings, as REFGND may by different from the other grounds by up to 0.3 V. But my question is whether it will work as intended, which is: the CAD mid code should be output as 0 V and swing should be even about 0V. Any other problems with this scenario ?

Regards, Tobi

  • 0
    TI__Guru 53773 points

    Hi Tobi,

    We do not recommend that you use a higher potential for REFGND than AGND and SGND.  The REF and REFGND should not be considered a differential input, but rather REFGND only denotes that this pin has the ground return current, and should be routed to the reference as well.  We explicitly recommend that the SGND pins be connected directly to to the REFGND pins for the corresponding DACs.

    Thanks,

    Paul

  • 0 in reply to Paul_Frost
    Prodigy 150 points

    Thank you, Paul,

    one question though, before closing this: Do you have DAC parts comparable to the DAC8734, which do have such a differential REF ? Such functionality is sometimes observed on ADCs, e.g. ADS1278.

    Regards, Tobi

  • 0 in reply to tobias kosub
    TI__Guru 53773 points

    Hi Tobias,

    Are you concerned about ground offset voltages? Or do you want to have an offset on the output as well?

    The DAC81408 has some REF ground offset capability.  Check out section 10.1 in the PDS.