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INA220: Failure of current shunt monitor device, potentially do to inrush currents.

Part Number: INA220

Hello,

I designed in IN220 current monitors into a 12v power distribution PCB. I used the the device on the high side, and without the "optional" resistors and capacitor on the differential sense lines. 

What appears to have happened to me is when placing a fuse there was a inrush current that caused enough of a spike on the differential lines to cause the ESD protection to shunt energy to ground (12v across the part), destroying the component and damaging the PCB. There was a situational described in the datasheet which was used the example of sudden low resistance short to ground, but otherwise described what could of happened to me with a huge sudden differential value.

I found a application not talking about transient suppression that states small resistors combined with TVS diodes were the best mode of protections. 

My questions are

- Does this sound feasible for a mode of failure?
- Would it be advised to add the TVS and small <10ohm resistors to avoid this scenario?
- Why is protection only as optional instead of more clearly recommended.

I mostly just want confirmation that this seems reasonable, adding the protection should solve it, and that I am not chasing the wrong issue.

Thanks

  • Hello Travis,

    Thanks for choosing a TI product. I think this is a very reasonable failure mode and solution. Although I am not sure where you a placing the fuse and whether you are exceeding the absolute maximum common-mode (-0.3V to 26V) or maximum differential voltage (-26V to 26V) ranges. The INA220 datahsheet does not have much transient protection information, but the INA181 datasheet shows how to implement this.

    Here are some more article that could be helpful for you.

    http://www.ti.com/tool/TIDA-00302

    http://www.ti.com/lit/ds/symlink/ina181.pdf

    http://www.ti.com/lit/an/slyt492/slyt492.pdf

    http://www.ti.com/lit/an/slla305/slla305.pdf

    Hope this helps. Post back if you have more questions.

    Peter Iliya

    Current Sensing Applications

  • In reply to Peter Iliya:

    Thanks, I appreciate that it sounds like I am on the right track if what started the failure and how it might reasonably be solved.

    The fuse I am speaking of connects incoming 12v (after the shunt) to the 12v bus. Meaning the shunt monitor could monitor pre-fuse voltages. The reason is I can compare bus against incoming voltages for blown fuse detection. When placing the fuse without any other supplies I am guessing a large inrush happens to energy the entire bus and apparently enough to cause the ESD protection to breakdown.

    Per the "typical" circuit I did not use inline resistors or protection diodes, as I was only expecting small voltages due to the differential sense of the shunt, but if the shunt shorts to ground through it's own protection, 12v would then be seen internally and I am thinking this is where the issue cascaded into a failure.

    Thanks again!

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