INA237: The violation at VCM negative voltage when the low side detect

Leo Yang

Expert 4825 points

Part Number: INA237

Hi team,

My customer measured the waveform when the power in is pluging-in.

They found the IN+ and IN- are over -0.3V. They probes the sense resistor and IC ground. Please find the waveform.

Do you have any concern about negative voltage? Our datasheet mentioned -0.3V negative for VCM.

If this is out of our spec, could you help to suggest a work around circuit. I can sent you the SCH offline.

Do we have the higher voltage limitation while in short pulse voltage/current for INA237?

Or what is the acceptable voltage spike range with low energy pulse?

Thanks,

Leo

over 1 year ago

0 Mohamed Hamida over 1 year ago

TI__Expert 6602 points

Hi Leo,

This would be out of spec and could cause unpredictable behavior. You should consider using our digital isolation TI reference design which helps combat this: https://www.ti.com/lit/ug/tidu361a/tidu361a.pdf?ts=1713566587213&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FINA226

Best,

Mohamed

0 Leo Yang over 1 year ago in reply to Mohamed Hamida

TI__Expert 4825 points

Hi Mohamed,

The customer have the isolator in the SCH. I am sending you the SCH offline. Please help to check.

May I know the reason the digital isolator could help this issue? Thank you.

Leo

0 Guang Zhou over 1 year ago in reply to Leo Yang

TI__Mastermind 32480 points

Hi Leo,

We don’t have a similar digital power monitor that can withstand -1V. There is not a safe operating spec on out-of-range spike/duration either.

Customer could insert a 150Ohm resistor in front of each of the input pins. These are slightly larger than typically recommended, but I think it’s OK and they will help mitigate the impact of these spikes.

Regards, Guang

0 Mike Liu1 over 1 year ago in reply to Guang Zhou

Prodigy 80 points

Hi Guang...

You mean RFILTER:150 Ohm ?

Thank you!!

0 Guang Zhou over 1 year ago in reply to Mike Liu1

TI__Mastermind 32480 points

Hi Mike,

Yes, that’s correct.

Regards, Guang

0 Mike Liu1 over 1 year ago in reply to Guang Zhou

Prodigy 80 points

Thank you!!

0 Leo Yang over 1 year ago in reply to Mike Liu1

TI__Expert 4825 points

Hi Guang,

The customer has tried 100ohm and 1kohm at the series resistors. It seems the negative voltage still up to -1V.

This is the result tested under 1k ohm and Cfilter=1uF.

Thanks,

Leo

0 Guang Zhou over 1 year ago in reply to Leo Yang

TI__Mastermind 32480 points

Hi Leo,

The purpose is not to reduce the negative voltage. The resistors are to act as a current limiter if and when the INA237 internal circuitry is activated, thereby protecting the device.

Regards, Guang

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INA237: The violation at VCM negative voltage when the low side detect