Precise overvoltage limit

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Hi!

I have a problem: I have a 24V power supply and I want to measure the current of it with the Texas Instruments INA209.
The INA209 has for voltage an absolute maximum rating of 26V.
I would like to have an overvoltage protection in front of the INA209, which shold be a pretty precise overvoltage protection, since 24V is the normal operation, and 26V is the absolut maximum of the INA209.

I have looked at the TVS diodes, and Zener diodes, but all of them have a greater tolerance than what is needed here.

Has anyone a simple solution for this? Is there a special IC for it?

Thanks!

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Almost every "precision" over-voltage protector is going to add to the series output resistance of the power supply.

I think I would advise looking for a different current sensor that is more tolerant of voltages above 24V. I'd be willing to bet that the precision voltage limiter will cost you a lot more than changing sense ICs. No suggestions.

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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Following Jim's advise, what about the MAX4172 as a high-side current sensor, rated up to 32V?

Einstein was right: "Two things are unlimited: the universe and the human stupidity. But i'm not quite sure about the former..."

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AD8212 is 65V

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We have a battery application using the INA209, the nominal voltage is 27.6V. In the design phase it was difficult to find an alternative chip with higher voltage rating so we decided to try the "overloaded solution".

It now has worked without problems for four years. It even handle battery charge cycles up to 35V.

The equipment does not run continuously, i guess the total run time is 2000 hours and there is four units running at the same time.

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what is the "overloaded solution"?

Precision overvoltage does not exist, just like precision over current does not exist.

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toalan wrote:
what is the "overloaded solution"?

Precision overvoltage does not exist, just like precision over current does not exist.

The overloading solution was to ignore the specification from Texas Instruments. We simply stated that the chip is able to handle 2 more volts, but it was at our own risk, the application is for research purposes, not anything we sell to a customer.

But the chip handled up to 35V which is good :)

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touche, that is strong kung fu

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i do not think that this chip has a normal operating range specified to 24V and then a absolute maximum rating of 26V.

what is the maximum specified normal operating range ??? This is what you need to maintain. Going beyond those limits the device is probably not yet destroyed(that is the absolut max rating) but might not do what it is supposed to do according to the specification..

keep that in mind.....

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Hi!

Thanks for the advices.

Quote:
i do not think that this chip has a normal operating range specified to 24V and then a absolute maximum rating of 26V.

Neither do I, but the datasheet says it.

Quote:
Precision overvoltage does not exist, just like precision over current does not exist.

Why not? Precision means in this case, that it cuts every spike above a certain value, and cuts EXACTLY there.
Probably you are right in that sense, that this is more like a linear regulator, than an overvoltage protection.

Quote:
I think I would advise looking for a different current sensor that is more tolerant of voltages above 24V.

This would be a good idea. Requirements changed lately, and I already have 20 of INA209.

Finally I found an acceptable solution: I found, that I can adjust my power supply to 22V (which is sufficient luckily), so I can use 24 Zener diode.