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TLV5618A output current source/sink

Carl Reese
Prodigy 230 points
Other Parts Discussed in Thread: TLV5618A

Greetings:

I've attached a pdf schematic to reference with my questions.

My questions are:

1.  The datasheet includes curves that indicate the maximum sink and source currents for this device.  In the attached pdf, the DAC has a 1K resistor pullup on the analog output of the TLV5618A.  This seems to violate the output sink current guidelines in the datasheet.  Am I correct?

2.  When the TLV5618A first powers up, what is the output voltage value, prior to the first time the DAC is written to over the serial link?

3.  Is there a reason for needing the 1K pullup resistor that I am missing?

Thanks

Carl Reese

214-794-4897 cell;DAC_V_I.pdf

  • 0
    TI__Genius 10615 points

    Carl Reese said:
    In the attached pdf, the DAC has a 1K resistor pullup on the analog output of the TLV5618A.  This seems to violate the output sink current guidelines in the datasheet.  Am I correct?

    This is a pretty old device, so it's really hard to say what the maximum sink current is. The plots shown in the datasheet, show a max sink current of 2 mA. This doesn't always mean that the max sink current is indeed 2 mA, but it is a good estimate.

    The 1kΩ pull-up is indeed very strange. I can't think of a good reason for it to be there. It will indeed cause excessive current sink into the DAC output. I would suggest removing it. It will cause current draws between 1 mA - 5 mA which will at the very least degrade the performance of the device, and at worst it can burn the device.

    Carl Reese said:
    2.  When the TLV5618A first powers up, what is the output voltage value, prior to the first time the DAC is written to over the serial link

    It power's on to zero-scale (0V) as stated on page 10 of the datasheet.

    Carl Reese said:
    3.  Is there a reason for needing the 1K pullup resistor that I am missing?

    None that I can think of. I don't see a good reason for it to be there.