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DAC121S101QML-SP: DAC121S101QML-SP: Voltage output transient seen during power up

Erik Laurila
Prodigy 180 points
Part Number: DAC121S101QML-SP

DAC121S101QML-SP:   During power-on, I'm seeing a voltage transient on the DAC output.  The transient is about 800mV and lasts about 2ms.  The DAC supply voltage is ramping up from 0V to +2V during this time (on its way to final voltage of +5V).  In the datasheet, it mentions that the DAC output is zero on power up.  So, I was not expecting to see any output voltage transient from this part.  Is this transient expected during power on when the supply voltage is below +2V?

  • 0
    TI__Genius 17035 points
    Hello Erik,

    Please see figure 27 in the datasheet.

    The DAC121S101QML-SP does have a power on reset that sets the output to 0 once that is functional once the supply reaches the part's operating range (2.7V min). The output does follow the input during the votlage ramp as you have observed and is shown in figure 27.

    Let me know if you have any other questions.
    Kirby
  • 0 in reply to Kirby Kruckmeyer96848
    Prodigy 180 points

    Is there any recommended way to suppress this?  I see the max output load capacitance is only 1500pF.  That is not enough to suppress this transient. 

    If I put an RC low pass filter, the resistance will isolate the capacitor so I can use a higher value correct?

  • 0 in reply to Erik Laurila
    TI__Genius 17035 points
    We have found that the slower the power up ramp the lower the output transient. For a power up rise time of 5V/ms the transient was under 200 mV.
    An RC filter on the output might also help mitigate the transient, but we have not characterized this.