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AMC7832: AVSSa connection

David Zhao
Intellectual 1820 points
Part Number: AMC7832

Hi Supporter

My customer adopt AMC7832 solution. In fact, they need to support negative DAC voltage range to about -5V. AVEE is connedted to -7V, VRANGEA is connected to 2.5V. But they do a wrong connection for AVSSA, AVSSA is connected to GND. Is it ok to support negative DAC voltage with AVSSa connected to GND or must connect AVSSA to AVEE? Thanks a lot!

Regards

David

  • 0
    TI__Intellectual 1820 points
    Hi Supporter

    As latest confirmation from customer, they can also accept positive DAC voltage. So the question is, for current connection, AVEE=-7V, AVSSA=GND, VRANGEA=2.5V, could it work normally? And what is DAC range for this connection?

    Regards
    David
  • 0 in reply to David Zhao
    TI__Guru 52663 points
    Hi David,

    Unfortunately that is not a valid configuration. The DACs in group A will assume the -10V range, but as they lack a negative supply, the output would be clamped to ~GND. Is group A the only group with the issue? It may be possible to disable the reference buffer, but I need to check with our design team to see if this is equivalent to grounding the range pin.

    I should get back to you shortly.

    Thanks!
    Paul
  • 0 in reply to Paul_Frost
    TI__Guru 52663 points
    Hi David,

    I checked with our design team - disabling the buffer would not be the same as grounding the VRange pin as the buffer is in a high impedance state when powered down. I think the customer will need to rework the board to resolve this issue.

    Thanks!
    Paul