current through FET

You need a low gate drive P-FET. The above P-FET is really only useful at Vgs above 4.5V. Such devices are not hard to come by.

You are on the right track looking at page 5 , 2nd graph. I'd imagine Farnell has an assortment on offer.

Maybe i'm over looking something, I don't see a problem unless your micro is not swinging to the rail? What I would worry about how ever is switching time. if it's not driving something at a constant pulse rate i think you should ok how ever, if you are doing such a process, a Gate driver maybe in order to force it on/off faster. THat's just my opinion, that is why I like experimenting with components before putting them in full use.

I will say how ever, Getting a lower (Ron) might be a better way to go.. I kind of think that unit's on resistance for switching is kind of high even at 0.35 ohms.

"

Assuming configured like the switching time test circuit on the datasheet....

Rdson = 0.35ohm...ok... Say 0.28V drop @ 800mA. So load only gets ~3V @ 800mA

The transfer shows Id ~ 800mA @ Vgs ~ -2.0V.

Does that microcontroller output apply >-2.0Vouts with respect to the source? Notice the on resistance spec. When Vg= -5V then you get the 350ohm Rdson. At Vg = -3V, it's a crappy 1 ohm or more.

Make sure Vg is right.

D from BC British Columbia Canada

It is too weak and does not have a guaranteed Rdson at 3.3V, assuming that's the gate swing you have available. Check out this one:

--
Regards, Joerg

http://www.analogconsultants.com/

The downside is that those cost around a Dollar in quantities. So if this is for production I'd check the other sources such as IRF as well.

--
Regards, Joerg

http://www.analogconsultants.com/

that's more like it! Got find :)

"

Same here. Best of all they let you sort by price. A quick twirl spit this one out, under $0.20 in quantities:

--
Regards, Joerg

http://www.analogconsultants.com/

IRF is usually what I use for things of this nature. (Logic Type Fets)..

--
"I\'d rather have a bottle in front of me than a frontal lobotomy"

"Daily Thought:

  SOME PEOPLE ARE LIKE SLINKIES. NOT REALLY GOOD FOR ANYTHING BUT
  THEY BRING A SMILE TO YOUR FACE WHEN PUSHED DOWN THE STAIRS.
http://webpages.charter.net/jamie_5"

(Completely OT) Do you have a leading space in the username on your new account? Google's archive is doing the strangest things with your posts.

On the front page of the group

you show up as "Anonymous".

Once the thread is opened,

your username disappears in the Thread frame as well as in the Body frame To see who posted, I have to click **More options**.

I checked, no leading space that I noticed. And yeah, it's not looking pretty on Google groups.. I was set up ok before. Then my system needed to be redone and had to reload all the software. I've made some changes for this post.. Maybe I have it right.

D from BC British Columbia Canada

I put in my old 'spam this' email address. Google groups is now appending to my usenet Google profile that goes back more than a year. 'D from BC' shows up on the top line too for my posts.

Let me know if it's still fumbled.

D from BC British Columbia Canada

That did it. Looking back, there was no email address listed. That appears to be what made Google barf.