Impact of exceeding maximum Drain-Source Voltage on a 2N7002BK MOSFET

[MixedSignalSystems]

I've had a bit of a project SNAFU with the enable circuit for a DC-DC regulator

I'm using a 2N7002BK N-Channel MOSFET with a 100kOhm pull-up resistor connected to the MOSFET drain pin. The MOSFET source pin is connected to ground.

Control signal (on MOSFET gate) goes high -> MOSFET is enabled -> DC-DC Regulator enable pin (on MOSFET drain) goes low ... Simple 

The pull-up resistor connects to the regulator input supply voltage. I've just realised that the supply can run up to 100V (rather than the 50V that I had previously assumed). The regulator can handle this but I'm not sure about the FET.

The Vds(max) on the 2N7002BK is 60V.

So, the 2N7002BK Vds could be ~100V, i.e. much greater than the 60V limit. The 100kOhm resistor will limit the current through the FET to the point where thermal effects of my mistake should not be problematic.

Are there any other voltage related effects that I should be aware of? Require consideration?

The board works but I'm worried about reliability. Is the FET going to fail early due to the excessive drain-source voltage?

Happy to hear people's thoughts or references for me to read, etc.

Thanks all.

[T3sl4co1l]

I would worry about progressive damage effects in avalanche, but if it's not overheating it's probably fine, at least for a good while.

I wouldn't have a problem running prototypes that way; I'd be leery of sending it out to customers though.  I would shop for a suitably rated replacement for the next run.

Tim

[anovickis]

Eventually you will poke holes in it, and it will stay conducting

How long exactly that takes is not easily known or an answer you should attempt to discover

[MixedSignalSystems]

Thanks Tim.

That is helpful. I'll remove the FET on the prototypes and leave the regulator running all the time.

Its a SOT23 package so finding a replacement should be doable.

[NiHaoMike]

What's the threshold on the enable pin? You could use a zener diode to limit the voltage.