Re: gEDA-user: [SOT] suggestion for a SMT switch

[Bob Paddock <bob.paddock@xxxxxxxxx>]

> Otherwise, look for the smallest MOSFET that will handle your current,
> as smaller size usually means smaller leakage current.  For example,
> the Fairchild 2N7002K (SOT-23) leaks 1 uA when off (Vgs == 0) but the
> 2N7002T (SOT-523) leaks only 1 nA when off.

Better check the Gate/Source (Vgs) turn on voltage of the 7002, it is
not the best at 3V (It is 2.5V Max).
It would be better to use something like the FDV305N that will turn on at 1.5V.

Also your impedance between the motor and the coil cell are not well matched,
unless you can put a big low leakage, low ESR cap across the voltage point
going to your motor/switch combo.   What will happen is you will turn
on the motor,
the voltage will sag from the coil cell to the point that your micro
resets, that then
turns off the motor, the low ESR cap will minimize this from happening.

Jason, you don't happen to be in the Cleveland area?  I'm having Déjà
vu  here with a very
similar discussion I just had with someone from a similar sounding
project, a couple of weeks ago.


-- 
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http://www.softwaresafety.net/
http://www.designer-iii.com/
http://www.unusualresearch.com/


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