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INA220: Negative power supply sensing with INA220

Louie
Expert 3180 points

Part Number: INA220
Other Parts Discussed in Thread: INA226, , LMP8601

Hello,

I currently have a -12V power supply I would like to monitor. I have noticed that this part has digital output with a negative differential down to -26V, but the CM limits it to about -0.3V. Are there any configurations that I could possibly take advantage of that will allow to use this device to monitor a -12V power supply? If not are there any other parts you would recommend, with digital or analog outputs?

Thank you.

  • 0
    TI__Genius 15770 points
    Hi Louie,

    We have a TI design that works for this application. It uses the INA226 device (similar to INA220) and an external circuit that enables you to measure negative voltages. Please refer to the following website. I design this circuit, you can contact me if you have any further questions.
    www.ti.com/.../tida-00313
  • 0
    TI__Genius 15770 points
    Hi Louie,

    Also, if your customer is open for analog output devices you can suggest LMP8601. The input common-mode voltage range is –22 V to +60 V when operating from a single 5-V supply.

    Hope this helps!
  • 0 in reply to Mayrim Verdejo
    TI__Expert 3180 points
    These are both excellent solutions, thank you so much
  • 0 in reply to Mayrim Verdejo
    TI__Expert 3180 points
    I was looking at the TI design and was wondering if there is a more simple way of doing this, I understand a lot of the external components are in place because it is to monitor 48V, which is well out of the common mode of both the INA226 and INA220.
  • 0 in reply to Louie
    TI__Expert 3180 points
    Would it be reasonable to say, that if I got ride of the transorb and resisitive divider, tie Vbus to 0V, and kept the zener as the TI design does, and follow the equation, I should be able to achieve this for a 12V design right?
  • 0 in reply to Louie
    TI__Genius 15770 points
    Hi Louie,

    I am guessing you meant (-12V). You can't tie Vbus to 0V because you need to use a resitor divider to scale the Vbus value and make changes in the software. This is all explained in the design, also how to select the values of the resistors depending on the Vbus voltage needed. The transorb is for protection purposes only, also explain in the document.
  • 0 in reply to Mayrim Verdejo
    TI__Expert 3180 points
    Hello,

    I can understand that you need to scale the voltage for the -48V design such that there is only 36V when referenced to the GND of the INA(-48V). But that's because the device is limited to 36V supply, for an application not limited by the supply, if I did not use the divider. For clarification, i want to tie GND_INA to -12V and Vbus to 0V.
  • 0 in reply to Louie
    TI__Genius 15770 points
    Hi Louie,

    Yes! I understood your question now. As long as you do not exceed the 36V range of the device you can get rid of the voltage divider and the transorb! I actually explain this on design document Page 6. The divider is only needed if you exceed the 36V. As far as how to do the connections, correct again. You should connect GND_INA to -12V and Vbus pin to 0V.

    Regards