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AMC7812: AGND vs ADC-GND vs DGND

Timothy Wiegman
Prodigy 10 points
Part Number: AMC7812

Which functions of this chip correspond to which of the three grounds? I assume the ADC inputs sink current to ADC-GND, but I'm not sure if, for example, the DACs use the DGND or the AGND.

Bonus points if you can tell me which specific pin of each ground for each function, if DGND+DGND2 and AGND1+2+3+4 (respectively) aren't tied together internally.

I'm only specifically interested in where the SPI interface sinks its current, and which ground the DAC uses for its reference; however, a full list posted here would be a good resource for engineers that may come across this post later.

  • 0
    TI__Guru 53773 points

    Hi Timothy,

    The grounds are connected internally, but we always recommend that they are connected externally as well.  (there is a higher impedance short between AGND, DGND, and ADC-GND).

    ADC-GND is really the negative reference for the SAR ADC.  There is some charge that goes through this point, but really it can be used as a differential input to the ADC.  For example, you can route this ground close to the ADC input source.

    The DGNDs are digtial input/output grounds, so digital switching current will return through these nodes.

    The AGND pins are grounds for the reference, ADC circuit, and DAC outputs. 

    Thanks,

    Paul