Zik Saleeba wrote:

>I was having a conversation with the chief design engineer at my place
>of work yesterday. He was saying he'd have to install an extra 3.3V
>voltage regulator in our design because I'd just discovered that we
>needed a second switched 3.3V supply. I suggested we used a high-side
>FET switch instead  - a suggestion he dismissed by saying the voltage
>drop across the FET was around 0.6V which would put the supply well
>out of spec.
>
>This man is a chief hardware designer of 40 years experience. I'm just
>a computer scientist who does electronics for a hobby. Am I crazy or
>is he completely wrong on this one? I'd be expecting a voltage drop in
>the millivolts at the low currents we're talking about - not 0.6V. Can
>someone set me straight here?
>
>Cheers,
>Zik
>  
>
When I think high side switch, I choose P-Channel devices.
(Pulling the gate to ground to turn it on.)
A random SOT-23 device with logic level and 1 amp.  NDS352AP
Do the math, the on resistance is less than an ohm, times the current, 
(60 ma.).

Tom

-- 
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  |  __O    Thomas C. Sefranek   WA1RHP@ARRL.net
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