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REF3040: Inaccurate voltage reference output

Part Number: REF3040
Other Parts Discussed in Thread: ADS8332

I refer to the ads8332 datasheet to design the voltage reference circuit, but the final output voltage is 20mV more, and my design voltage is 4.096V,where R239 is 0ohm

  • Hi Chengxin,

    Is your voltage reading from a simulation or from bench testing?

    If it is from simulation, can you share the environment used to make the simulation and where you got the vref model?

    If it was bench testing, can you give me the following voltage measurements (per the schematic):

    • Pin1 of the vref
    • Pin2 of the vref
    • Pin3 of the op amp
    • Pin2 of the op amp

    It would be helpful to get scope shots of this, too, since you have a lot of capacitance at the output of the op amp.


  • HI  tony:

    My voltage reading is from bech testing.My tool is Anglent 34410

    Pin1 of the vref 5V
    Pin2 of the vref 4.097V 
    Pin3 of the op amp 4.097V
    Pin2 of the op amp 4.121V

    This scheme is from the datasheet of ads8332

  • Hi Chengxin,

    Thanks for providing the details for me.

    I am looking into this - I will get back to you shortly. 


  •  HI Tony:

    Mybe I know the reason,the AMP(op27GS) is not a rail to rail AMP

  • Hi Chengxin,

    I have a feeling I know what the issue is - my guess is that the supplies of the op amp are flipped. V+ should be 5V and V- should be 0V. Can you confirm which pins are the V+ and V- and measure them?

    If they are indeed flipped, reverse them (assuming the op amp is not killed) and take the measurements. You may need to replace the op amp if it was killed.