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DAC714 Offset adjustment

Russ Beech
Prodigy 20 points
Other Parts Discussed in Thread: DAC714

Page 10 of the DAC714 data sheet illustrates how to use four external resistors and two external potentiometers to adjust the gain and offset of the DAC.  I am using this circuit with pin 10 unconnected to get +/- 10 V output range.  I find that the offset adjustment is completely ineffective as described in the data sheet (the data sheet says to use the offset adjustment with the DAC set for maximum negative output, i.e. -10 V in my case).  Even at midscale - or 0 V output - the offset adjustment has almost no effect.  Has anyone found a circuit modification (different resistor or potentiometer values) that provides a usable offset adjustment?

  • 0
    TI__Genius 10615 points

    Hi Russ,

    How are you measuring the offset of the DAC?

    This circuit is able to vary the offset by 0.3 %FSR.

    Are you using the same resistor sizes?

  • 0 in reply to Eugenio Mejia
    Prodigy 20 points

    Eugenio,

    I am using a Fluke DMM to measure the DAC output.  I am using the same resistor and potentiometer values as shown in the data sheet.  The only difference in my circuit is that pin 10 is unconnected so that I get +/- 10 V output range (does this change the required resistor values?).  The gain adjustment was able to move the output the roughly 10 mV needed to get to +10 V at code 0x7FFF.  The offset adjustment could not move the output even 1 mV at code 0x8000.  At code 0x0000 (midscale, should be 0 V output)  the offset adjustment was able to move the output a couple of mV.


    I'm assuming FSR = "Full Scale Range", or something like that.  Is this correct?  With a range of 20 V (+/- 10 V), 0.3% would be 60 mV.

    Russ