When measuring my 24V power supply I found that its voltage spikes up to ~29V before stabilizing to 24V when I first plug it in. It lasts a fraction of a second but I feel like it is cutting it very close to my MOSFETs maximum Vds (30V):
https://assets.nexperia.com/documents/data-sheet/PSMN017-30EL.pdf
The circuit has been working fine so far but I am worried that there will be one time where it spikes higher and it destroys all of my MOSFETs. Can NMOS withstand that kind of voltage spike? The MOSFETs are all off (no voltage to gate) when this happens if that matters.
Thanks

 

You should use a higher rated FET.

 

When measuring my 24V power supply I found that its voltage spikes up to ~29V before stabilizing to 24V when I first plug it in. It lasts a fraction of a second but I feel like it is cutting it very close to my MOSFETs maximum Vds (30V):
https://assets.nexperia.com/documents/data-sheet/PSMN017-30EL.pdf
The circuit has been working fine so far but I am worried that there will be one time where it spikes higher and it destroys all of my MOSFETs. Can NMOS withstand that kind of voltage spike? The MOSFETs are all off (no voltage to gate) when this happens if that matters.
Thanks

It may also depend on how you are doing the measurement and what instrument you are using. It is just barely possible you are seeing things that are not really there.

 

Are there zeners in a suitable voltage range that could be used to clamp the spike somewhere between 24 and 30V? Or maybe a couple zeners in series to achieve the desired voltage if an exact match isn't readily available?

Just brainstorming - I don't know what's out there, or whether the response time would be fast enough for it to do any good, or whether it's even necessary, etc...

 

When measuring my 24V power supply I found that its voltage spikes up to ~29V before stabilizing to 24V when I first plug it in. It lasts a fraction of a second but I feel like it is cutting it very close to my MOSFETs maximum Vds (30V): https://assets.nexperia.com/documents/data-sheet/PSMN017-30EL.pdf

For a 24V circuit, using MOSFETs with a Vds(max) of 30V is asking for trouble; that's nowhere near enough safety margin. My own preference (others may disagree) would be to use a device rated at no less than 50 volts.

The circuit has been working fine so far but I am worried that there will be one time where it spikes higher and it destroys all of my MOSFETs. Can NMOS withstand that kind of voltage spike?

The best practice is to take Absolute Maximum Ratings (or Limiting Values, as they are called in your data sheet) literally, and heed the warnings associated with them:

Limiting values — Stress above one or more limiting values (as defined in
the Absolute Maximum Ratings System of IEC 60134) will cause permanent
damage to the device. Limiting values are stress ratings only and (proper)
operation of the device at these or any other conditions above those given in
the Recommended operating conditions section (if present) or the
Characteristics sections of this document is not warranted. Constant or
repeated exposure to limiting values will permanently and irreversibly affect
the quality and reliability of the device.

To do otherwise is to court disaster.

 

I'm not one of the "others" (totally agree with your point). I'd say 50V is probably the lowest I would consider. In a part search I'd look up to 100V and pick based on best specs. Since you often get a price break at 10, I'd consider even higher max V so I have a stock of parts that might be usable in other projects as well. (I always buy at least one more than I need anway in case the blue smoke leaks out)

On absolute max ratings. These are extreme and you should never, ever be testing those limits in your circuits. You may not blow a circuit immediately but that's actually worse as the failure will come later when you least expect it and can cause additional damage to other components.

 

In a part search I'd look up to 100V and pick based on best specs. Since you often get a price break at 10, I'd consider even higher max V so I have a stock of parts that might be usable in other projects as well.

One thing to watch out for when doing that, though: once you get above a hundred volts or so of Vds(max), Rds(on) often takes a hit: whereas low-voltage MOSFETs can have ON resistances in the low milliohms, high-voltage units often are in the hundreds of milliohms or even higher.

 

yeah, that's why I said "and pick based on best specs". Actually the key spec with Rdson is with respect to Vgs when you are interfacing to logic (which is about all I do). The data sheets often promote a low Rdson when, in fact, that is with a Vgs of 10V. For a Vgs of 4.5V it's often kind of sucky.

But on the other hand, if you aren't pushing a lot of current, Rds isn't that important.