Author Topic: min Vds for automotive use  (Read 3554 times)

0 Members and 1 Guest are viewing this topic.

Offline SimonTopic starter

  • Global Moderator
  • *****
  • Posts: 18031
  • Country: gb
  • Did that just blow up? No? might work after all !!
    • Simon's Electronics
min Vds for automotive use
« on: November 27, 2010, 02:46:13 pm »
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.
 

Offline qno

  • Frequent Contributor
  • **
  • Posts: 422
  • Country: nl
Re: min Vds for automotive use
« Reply #1 on: November 27, 2010, 10:08:11 pm »
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.
Why spend money I don't have on things I don't need to impress people I don't like?
 

Offline SimonTopic starter

  • Global Moderator
  • *****
  • Posts: 18031
  • Country: gb
  • Did that just blow up? No? might work after all !!
    • Simon's Electronics
Re: min Vds for automotive use
« Reply #2 on: November 27, 2010, 11:51:41 pm »
but the question being will the 30V mosfet survive an automotive environment ? thats from source to drain
 

Offline tyblu

  • Frequent Contributor
  • **
  • Posts: 287
  • Country: 00
    • blog.tyblu.ca
Re: min Vds for automotive use
« Reply #3 on: November 28, 2010, 12:10:14 am »
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.
Tyler Lucas, electronics hobbyist
 

Offline SimonTopic starter

  • Global Moderator
  • *****
  • Posts: 18031
  • Country: gb
  • Did that just blow up? No? might work after all !!
    • Simon's Electronics
Re: min Vds for automotive use
« Reply #4 on: November 28, 2010, 08:53:36 am »
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
 

Offline Zero999

  • Super Contributor
  • ***
  • Posts: 19933
  • Country: gb
  • 0999
Re: min Vds for automotive use
« Reply #5 on: November 28, 2010, 09:44:12 am »
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.



 

Offline SimonTopic starter

  • Global Moderator
  • *****
  • Posts: 18031
  • Country: gb
  • Did that just blow up? No? might work after all !!
    • Simon's Electronics
Re: min Vds for automotive use
« Reply #6 on: November 28, 2010, 09:53:26 am »
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
 

Offline Zero999

  • Super Contributor
  • ***
  • Posts: 19933
  • Country: gb
  • 0999
Re: min Vds for automotive use
« Reply #7 on: November 28, 2010, 10:03:44 am »
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 VDS rating is exceeded and the MOSFET conducts when it should be in the off state.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf