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DAC61416: Headroom For Current Sink

Ray Vincent Aranzaso
Genius 16780 points
Part Number: DAC61416

Hi,

I'd like to ask, if there is always a negative voltage at the Vss pin needed for sinking current. I'd like to use the following network:

+5V---------250R--------DAC61416 (@0V).

The current through the resistor would be 20mA. Can the DAC61416 sink the 20mA, if the Vss pin is at 0V?

Best Regards,

Ray Vincent

  • 0
    TI__Guru 53583 points

    Hi Ray,

    The DAC can source (current flowing out of the DAC) 20mA with about 2V headroom/footroom.  So assuming you have VCC>9V and VSS = 0V, then you should still be okay when the DAC is at 5V.  You would have trouble sourcing the current if your output was lower than 2V.

    Thanks,

    Paul

  • 0 in reply to Paul_Frost
    TI__Genius 16780 points

    Hi Paul,

    Good Day. Please see below the response of our customer to your reply. Thank you very much.

    But I asked if it's possible to sink current with 0V footroom, not to source current. My question was if the DAC61416 can sink current (25mA), when the output of the DAC is at 0V and Vss = 0V and current flows from a higher potential into the DAC.

    Best Regards,

    Ray Vincent

  • 0 in reply to Ray Vincent Aranzaso
    TI__Guru 53583 points

    Hi Ray,

    Sinking current with no footroom is generally a problem.  They will see a DC shift in the output that is proportional to the current being sunk.

    This plot shows the expected shift.  You would see a voltage on the output of about 1V.  If the customer wants to have sinking capability at 0V, they will need to provide a negative VSS supply of at least -1V, but -2V is recommended.

    Thanks

    Paul