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INA240-Q1: The output was abnormal because ref pin voltage abnormal

Harry Ma
Intellectual 2750 points
Part Number: INA240-Q1
Other Parts Discussed in Thread: INA240

Tool/software:

HI Team

Customer uses this device for high side current sensing. 

CM=80v, the frequency of current is 300KZ,  V-ref =0.3V and get it by dividing from Vs.

They found the device is easy to occur output abnormal because of V-ref is not stable（Vs is stable）. and it will work abnormal when exchange one new device or it works with DC input current sometimes.

Can you give me some insight why this happen? and which direction I should check?

  • 0
    Guru 318700 points

    The REF pins are connected directly to the internal resistor network, so the current through these resistors will load the external divider.

    Use a much higher current through the divider, or buffer the reference voltage with an opamp.

  • 0 in reply to Clemens Ladisch
    TI__Mastermind 35290 points

    Hi Harry,

    An unstable REF is definitely not a good thing. Please consider a buffer as Clemens suggested. The other factor could be that the 300kHz signal might be too fast for INA240. Distortion and gain drop starts to get bigger.

    It is probably a good idea to separate the two and attack individually.

    Regards

    Guang