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INA210 GAIN Issue

Mark Sun
Prodigy 130 points

Other Parts Discussed in Thread: INA210

I am working on power converter and use TI INA210 as current sense. The current sense voltage is from 0 to 12.5mv and the supply voltage is 12v. The gain should be 200, but the measurement shows 175 and 158 for two units. Can you explain this and suggest a solution? 

Thanks,

Mark

  • 0
    TI__Genius 14825 points
    Mark,

    To best help you, I'll need a few bits of information to start debugging.

    1. How much current are you trying to measure, and what is your sense resistor size?
    2a. Are you using the EVM or do you have a proto-board or custom layout?
    2b. If it is custom, would you provide me the schematic (or at least the applicable section)? If it is confidential, please send it to bridgmon_jason@ti.com.
    3. Is there an input filter with series resistors and a capacitor? If so, what sizes?
    4. Is the common mode of the input signal also 12v or something else?
    5. What is the VREF value?
    6a. At 12.5mV, the expected output is 2.5v. Can you confirm you are getting 2.19v and 1.98v output?
    6b. Does this gain hold linearly as Vsense is swept between 0 and 12.5mV?
    7. What is the output driving?

    Thank you!
    Jason Bridgmon
  • 0 in reply to Jason Bridgmon
    Prodigy 130 points
    the current is from 0 to 100A. This is real application for my power supply. I just send you the schematics by e-mail. The measured gain is 175 and 158 for two units and the gain is linear as Vsense changes from 0 12.5mv. The output with a RC filter and voltage divider drives the microprocessor input.
  • 0 in reply to Mark Sun
    TI__Genius 14825 points
    (To the community following this thread)

    When debugging and validating a design by measuring the sense voltage on the inputs of the Current Shunt Monitor and correlating it to the output, you must measure at the input pins of the device. Measuring at test points or across the shunt resistor itself will often yield poor results.

    It is also important to use a landing pad layout for the shunt resistor that incorporates Kelvin connections so that as little current as possible (besides input bias current) flows through the traces. Doing this improves accuracy.

    Jason Bridgmon