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DAC8728: GND problem

Hans Wu6
Prodigy 60 points

Part Number: DAC8728

Hi,

In the PIN DESCRIPTIONS section, The pin name AGND's description

I want to know why the AGND-A or AGND-B is need to tied DGND? 

If I let they separate but short AGND and DGND at other place on PCB, will DAC8728 work?

Thanks!

  • 0
    TI__Mastermind 46290 points
    Hans,

    In the end the digital circuits control and interface the analog circuits inside the device. Therefore, they need to be sharing a common reference voltage, which we all conventionally refer to as ground. Additionally, based on the datasheet, it would appear that there are some diode connections between AGND and DGND, most likely for ESD purposes, which would conduct if the two nodes were separated by more than 300 millivolts.

    You may separate the two in your PCB layout so long as they are shorted somewhere, either on the board or via connectors. This is a topic of much debate in mixed signal circuit design & fabrication, but there are "schools of thought" which argue many different approaches varying from star grounds, split grounds, single grounds etc. In my experience this relates more to how the signal traces are actually routed versus anything with the ground planes.