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INA381: Clamp for Negative Common-Mode Transients

Peiheng Liu
Prodigy 620 points
Part Number: INA381

Hi,

I am looking for a shunt-based over-current protection solution for battery pack application. The figure 50 of INA381 datasheet fits right in customer needs. The nominal voltage of PACK+ is ~ 50V so the current sensing feature would be implemented on the low-side.

INA381 specifies a -0.3V negative common-mode voltage limit in the datasheet. However in such battery protection circuitry there would be some negative swing on the PACK- terminal during over-current cutting off. I think adding some schottky clamp to INA381 GND would work for this situation. Could you please help to share some ideas about clamping the negative swing on INA381 IN+/IN- pins? 

Peiheng.

  • 0
    TI__Mastermind 32395 points

    Hey Peiheng,

    I have a FAQ post about this exact need for current sense amplifiers. The links for this are below and discuss general options available. Note that in the solutions I present here I include 10Ω resistors to limit the current into the clampling diodes, but customer may want to consider adding another pair of 10Ω resistors directly at the inputs IN+ and IN-. These would limit current into the devices, which will help improves robustness. I have included the schematic of what I am suggesting below. I have not proven this will work or there are Zener diodes available with correct reverse bias break down to support this. I inlcude this schematic so customer will know what I am trying to suggest with the extra input resistors.

  • 0 in reply to Peter Iliya
    TI__Mastermind 27715 points
    Hi Peiheng,

    It's been over two weeks since your last post, so it seems like your issue has been resolved. I will close the thread for now. If you have any further questions you can reply to re-open it, or start a new thread with a new question.

    Best regards,

    Ian Williams
    Applications Manager
    Current & Magnetic Sensing
  • 0 in reply to Ian Williams
    TI__Prodigy 620 points
    Hi Ian,

    The summaries from Peter is very helpful. Apologies for the delay response since I am in the new year holiday these days. I would get back to your for another discussion if necessary. Great thanks for your help!

    Peiheng.