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INA819: Simulation output with single supply not matching expectation

Part Number: INA819

Team,

my customer has issues with the model for INA819. The model does not provide expected output if the model is supplied with a single supply. (For example: 5V DC)
The datasheet mentioned the device is capable of operating at single supply voltage.

Could you please check and clarify if it is just the limitation of the model!

Thanks!

  • Hi ,

    Please see the attached Tina simulation. With single supply of 5V, the input common mode voltage range is somewhat limited at Gain=1. I placed 2.5V reference at pin 6, shown in Figure 58 and 59.  

    OPA810 Single Rail 03022020.TSC

     Best,

    Raymond

  • Raymond, thanks for your quick response!

    Not sure if I understand this correct:

    Is the model behaving as expected with single supply?
    Do you recommend a 2.5V reference voltage for the design?

    I do not have a precise description of what the customer tried to do and what they expected, so I guess I am missing crucial details here.

  • Hi franziskus,

    Questions:

    Is the model behaving as expected with single supply?

    Do you recommend a 2.5V reference voltage for the design?

    Yes, see the attached image. With 5Vdc single rail supply, the (V-)+2 < Vcm < (V+)-2 as operating input range. With Vref=0, the output voltage range is determined by Vo=G(V+in - V-in).

    If the Vref is biased up to 2.5Vdc at the output, the output voltage and Vcm can be increased as shown in figure 51 and 52 of the datasheet. 

    Vref is recommended as low impedance source, so it will not mess up the last op amp gain stage. If you do not have 2.5Vref on board, you may use 2.5Vdc buffer, but it need to be stable, not influenced by changes in temperature, noise and drift. 

    Ground Vref may be the best option, then you have to use dual supply voltage rail. 2.5Vref will be the second best options for a single voltage supply rail. 

    Best,

    Raymond

  • Thank you for your great Raymond!

    Your answers + offline follow-up resolved the issue and customer has adjusted their design accordingly.