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INA296A-Q1: INA296A4 and INA296B4

Vlad Tap
Prodigy 10 points
Part Number: INA296A-Q1

Tool/software:

Hello there,

I am trying to measure a voltage drop across a shunt and am using INA296A4 (tried also with B4 version) and the gain is nowhere near 100. Instead i keep measuring a gain of 4 to 6 and sometimes even around 1. I have tried also connecting the device externally to a supply and supplied a voltage at the IN+ and IN- of 10mV and the output was around 10mV as well ( I assumed maybe my Layout is having a negative effect). When increasing the IN+ and IN- voltage, the gain increases to around 4 or 5. I get the same effect if I supply a current through the shunt - nothing changes and the gain is at most 4 to 6. 

Do you have any suggestions or maybe ideas what could be wrong? Would really appreciate some input. For further questions, please let me know. Here is the Circuit and a picture of the Layout:


Ref 1 and 2 are connected to each other and to an external voltage reference IC of 2.5V ( which delivers 2.499V)

 


  • 0
    Prodigy 10 points

    thanks a lot for your help in advance and let me know if I can provide further useful info, to better understand the situation.

    Cheers,
    Vlad

  • 0
    Guru 280970 points

    What are the voltages you are measuring at the five input/reference/output pins?

  • 0 in reply to Clemens Ladisch
    Prodigy 10 points

    Hi Clemens,

    so IN+ to IN- is 10mV, Vref 2,49V and Vout is around 2,58V. 

    With higher In+ to IN- the gain goes towards 5 or 6.

    Thanks for your time

  • 0 in reply to Vlad Tap
    TI__Mastermind 29560 points

    Hello Vlad,

    Are you able to measure directly at the pins of the device after your R2 and R3?  What is the VCM(Voltage with respect to GND pin) at the input pins?  What is at the output of the INA296.  Is there a large capacitance at the output?  Please make sure the capacitor is smaller than 1nF unless you have an isolation resistor greater than 200Ω.

    I mentioned all the things I would look for with the information provided.  I do not expect the device to have these issues based on my use of this device and many debug with other users of this device.

    Regards,

    Javier