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INA229-Q1: Shifting ground reference for near 85V applications

Asith Devinda
Prodigy 60 points
Part Number: INA229-Q1
Other Parts Discussed in Thread: INA229

I'm using the INA229 in a battery system which can reach up to 80V when fully charged. Since this is close to the maximum allowable common mode voltage or Vbus voltage of the device, it is risky. I was thinking of shifting the ground reference by half using a voltage divider, say two resistors of 220Ohm to minimize power draw, and using the device at high side. I tested it and seems to work OK while giving a Vbus reading of half the actual bus voltage. Are there any drawbacks to this method? Are there any other options I should try?

  • +1
    TI__Mastermind 22275 points

    Hello Asith,

    Since the INA229 can go up to 85V, then you may just be able to use it normally at 80V, as long as you don't expect high voltage spikes.  You could also use some protection diode to prevent the VCM spikes from going over 85V. This way you are protected from spikes, but don't need to divide your voltage. 

    In general, the INA GND will need to be the same potential as the MCU for digital communication, so this could work as long as you are accounting for that. You may be interested in this TIDA: https://www.ti.com/tool/TIDA-01608, which shows how to use a VCM outside of the device range. (but I think some protection diode would be a better approach, since you don't plan to go above the 85V).

    Regards,

    Mitch

  • 0 in reply to Mitch M
    Prodigy 60 points

    Thank you Mitch.