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Transient voltage protection where Vtyp is close to your IC Vmax
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Psi:
I have an application where the circuit absolute max voltage is 42V but the operating voltage will be around 30V

I'm quite used to using 3kW TVS diodes but all the ones i can find have their working voltage and clamping voltage further apart than that.

So my question is, what other transient voltage protection approaches are there for dealing with this sort of situation?
David Hess:

--- Quote from: Psi on September 13, 2020, 03:21:01 am ---I have an application where the circuit absolute max voltage is 42V but the operating voltage will be around 30V

I'm quite used to using 3kW TVS diodes but all the ones i can find have their working voltage and clamping voltage further apart than that.

So my question is, what other transient voltage protection approaches are there for dealing with this sort of situation?
--- End quote ---

A series regulator or shunt regulator or both can work.  The problem then becomes achieving a quick enough response.
 
Alti:

--- Quote from: Psi on September 13, 2020, 03:21:01 am ---I have an application where the circuit absolute max voltage is 42V but the operating voltage will be around 30V
--- End quote ---
Do you want the device to work undisturbed at 42V supply and die at 43V or do you want it to shut down at 31V and die at 1kV 8/20us? Just describe the test this device is intended to survive (and die at +1V) and then we can propose some solution.

As for TVSes you can use TVS for 14V nominal voltage. This will clamp to 43V (max) exactly one 8/20us transient (I took some random TVS datasheet). At 30V it is going to dissipate some power, now the question is do you care. If this is a uA application then 1W dissipation might be a problem but if it s 1kW then does it matter? Is it ok to survive exactly one 43V 8/20us pulse or maybe 1000 pulses is more adequate for this application? Because then you have to use TVS for higher voltage, etc.
Nauris:
Try how big transients it can actually take. It might be that ordinary TVS is good enought.
Siwastaja:

--- Quote from: David Hess on September 13, 2020, 10:47:28 am ---A series regulator or shunt regulator or both can work.  The problem then becomes achieving a quick enough response.

--- End quote ---

... and adding capacitance makes the "quick enough response" problem disappear.

Of course, with proper layout and minimized inductance. And preferably damped with higher ESR capacitance, say a smaller amount of ceramic with larger amount of electrolytic in parallel.
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