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Can I use INA210 to current sense negative rail?

Allan Hall
Prodigy 30 points
Other Parts Discussed in Thread: INA210

Hi,

I'm building a dual rail psu with +/-12 volt rails, max 2A per rail output. I'd like to build current sensing into both positive and negative rails, I've chosen INA210 zero drift shunt monitor on cost/performance basis.

It is suitable for high side and low side measurement, but I'm not sure how to wire it to get a positive output voltage (need 0-5V) when connected to a sense resistor on the negative rail. Is this possible?

LT6105 works fine in this application but is a larger package and slightly more expensive.

Thanks,
Allan

  • 0
    TI__Genius 14825 points
    Allan, Are you planning to reference the INA210 to ground or to -12V? It may be possible to do this since the device is bidirectional and the common mode range is -0.3 to 26 V, but let me confirm that and I'll let you know tomorrow. - Jason Bridgmon
  • 0 in reply to Jason Bridgmon
    Prodigy 30 points

    Hi Jason,  Either Ground or negative rail can be used for ref, I think ground would be better option though.  Can power it from +12v rail.

    I've just tried a few different configurations in TinaTi  and this seems to work, do let me know if there is a better solution

    Thanks, Allan

  • 0 in reply to Allan Hall
    TI__Genius 14825 points

    Allan,


    What you are showing in your simulation is that you have referenced the INA210 to -12V, making the power supply equivalent to +24V, which is absolutely acceptable.  The common mode of this circuit is more positive than -12.3V, which relative to the shifted power supply, is greater than -0.3V, which is also acceptable.

    I ran your simulation myself and found the output to be 4V, which is 200 V/V * 10mOhm * 2A, which is correct.  This circuit looks like a good option, The only thing I would recommend in the real circuit is to decouple V2 to Gnd as well.

    Thank you for using TI products!  Let us know if you have any further questions, we are happy to help.

    - Jason Bridgmon

  • 0 in reply to Jason Bridgmon
    Prodigy 30 points

    Jason,


    Thanks for the confirmation that the circuit is ok and everything is running within spec.

    Problem solved :-)

    Many thanks,

    Allan