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Original question:

DAC121S101: Output error questions

DAC121S101: DAC121S101 output sink current

Kenneth Aquino
Expert 1330 points
Part Number: DAC121S101
Other Parts Discussed in Thread: DAC60501

I would like to know if there is a curve of sink current versus output voltage for the DAC121S101, a 12-Bit voltage output R-R DAC.

There is a curve in the DAC60501 for that, I was just wondering if there is a similar curve for the DAC121S101.  I'm just sinking less than 1 mA.

/cfs-file/__key/communityserver-discussions-components-files/73/1641.Capture.PNG

  • 0
    TI__Guru 53773 points

    Hi Kenneth,

    I do not have that curve, but we can estimate it.  When the output is in the linear range (when it has enough of a voltage difference between the DAC output the supply rail), the slope of the output vs loading will be set by the output impedance (~1.3Ω in this case).  Once the loading gets high enough, it will hit the short circuit limit. 

    Consider the grey line in the graph above: the slope of the flat region is set the output impedance, and when it hits the short-circuit limit when it slews to the supply rails.

    On the green line, you see the behavior when you are not in the linear region.  The higher slope region is when the DAC is sinking current, but its output voltage is set to approximately 0V.  This means that there is not enough headroom for the output amplifier to operate. 

    In your case, you should not have much problems sinking 1mA with the DAC121x, except when you are operating near 0V or the VCC supply.

    Thanks,

    Paul