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INA225 High side sense for negative voltage

INg
Genius 3475 points
Other Parts Discussed in Thread: INA225

HI

I would like to confirm if i would use INA225 as the shunt AMP to measure upto 3A of current as below setup?

 

Ivan

  • 0
    TI__Genius 14825 points

    Ivan,

    The circuit violates the absolute maximum specs for the device and will both not work and probably damage the device.  I've drawn up a few circuits in TI-TINA to show you a few things about how to accommodate measurements below GND.


    First, I did the circuit basically how you drew it and simulated it.

    2475.INA225 - bad 225 setup.TSC

    Next I drew up a typical +30V to GND setup for the INA225, so you can see approximately what values we are going to try to recreate.

    4540.INA225 for customer.TSC

    Finally, I added a zener diode and essentially created a +5V Vcc from the -30V rail with a resistor and the diode to ground.

    7242.INA225 - good negative rail setup.TSC

    I hope this helps you with your circuit.  Thank you for using TI products!

    Jason Bridgmon

  • 0 in reply to Jason Bridgmon
    Genius 3475 points

    Hi Jason

    Thanks very much for the suggestion. It appears that the shunt amp circuit is "virtual grounded" to -30V.

    Do you have any reference for the translator, does it have to be isolated?

    Another question, does the GS0 and GS1 have to be -30V or 0V to be set correctly?

     

    Alternatively, is there any other parts which can achieve the same in a more straight forward manner?

     

    Ivan

  • 0 in reply to INg
    TI__Genius 14825 points

    Ivan,


    Yes, it is virtual grounded, as you say.

    The translator (I assume we're talking about the analog output) doesn't need to be isolated if you use something like a high voltage op amp circuit (or similar) to do the translation.

    GS0 and GS1 would be set to -30V and -25V, or rather, virtual ground and derived Vcc.

    Presently, I am not aware of any other current shunt monitors that will do this in a more straightforward manner.

    Jason Bridgmon