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current through FET

Discussion in 'Electronic Design' started by blanko, Apr 7, 2008.

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  1. blanko

    blanko Guest

    I am currently using this FET to toggle the power to a device. The
    device wants 3.3V.

    I have pin 1 (gate) going to my microcontroller, pin 2(source) going
    to a 3.3V regulator, and pin 3 (drain) goes to the device I am
    powering. The 3.3V regulator can provide 800 mA of output current
    and I need all of that going through the FET to the device I am
    powering. The problem is that when I take a look at the datasheet
    (page 5 , 2nd graph) I will only be getting a few hundred milliamps.

    Does anyone have a different part they can recommend or an easy way to
    modify my current setup to allow for a higher current?


  2. Adam S

    Adam S Guest

    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.
  3. Jamie

    Jamie Guest

    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."
  4. Joerg

    Joerg Guest

    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:
  5. Joerg

    Joerg Guest

    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.
  6. Jamie

    Jamie Guest

  7. Joerg

    Joerg Guest

  8. Jamie

    Jamie Guest

    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:

  9. JeffM

    JeffM Guest

    (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**.
  10. JeffM

    JeffM Guest

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