min Vds for automotive use

[Simon]

what would you recommend as the minimum max Vds voltage for a P channel mosfet (so already "floating" at 13V) in an automotive situation ? I'm looking for lowest Ron (1-10 mR range) so I'm left with stuff that is usually no more than 30 V. obviously I can include TVS diodes for protection.

[qno]

usually a P channel fet allows -20V.
The higer the On voltage the lower the channel resistance.
You can limit the gate voltage with a zener.

[Simon]

but the question being will the 30V mosfet survive an automotive environment ? thats from source to drain

[tyblu]

Really up to the datasheet and your circuit protection. I'm sure you've heard of a load dump (100V+ for ~0.5s) -- so long as you can buffer your system from an event like that, go for it.

[Simon]

Well I'd only have room for a few TVS diodes or similar sized protection. most of the time the mosfets will be on so any spikes should pass through them with no ill effect although during start up of the vehicle they will e off so I can't bank on that much

[Zero999]

MOSFETs will be able to withstand avalanche energy without failing.

If in doubt, connect a zener across the drain and source terminals.

Have you considered N-channel? If it's not going to be turned on continuously you could use bootstrapping.

[Simon]

yes I'd be putting in protection, TVS from both D and S to ground and yea a 20V zenner from D to S is not a bad idea. The mosfet will be on non stop during normal use, I did think of putting in a circuit to boost the voltage for a drive of a high side N channel fet but really not worth the hassle as I can get P channel 5.4 mR 30V mosfets in SOIC8 packages for £0.4 each

[Zero999]

MOSFETs will be able to withstand some avalanche energy without failing, see the datasheet for more information.

Corrected.

FYI avalanche energy is the power dissipated when the V_DS rating is exceeded and the MOSFET conducts when it should be in the off state.