piclist 2001\04\18\173055a >
Thread: Charge pump for LCD Vlc ?
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face BY : David VanHorn email (remove spam text)



At 10:38 PM 4/18/01 +0300, Peter L. Peres wrote:
> >I have used the PIC's crystal out pin before for this, no problem. I was
> >able to use an "extended temperature" type LCD this way.
>
>Uhh. Okay, you win the prize for simplicity ;-).
>However, do you need a broadcast license for this ?

Highly likely!  You're better off, if you must, to do a charge pump off one
of the I/O pins.


>This drove a standard inductor to obtain higher voltage.
>This was using 455kHz ceramic resonators on the PIC. It was noisy enough
>to make me think twice before using it again.

455k is getting a little adventurous, but I would only expect layout-driven
issues.
Gonna be a lot of RF current into that gate cap, and the source needs a
solid link back to the uP gnd and VCC pins.
I'm wondering if you were turning the fet fully on and off, since the
output drive on the pic is relatively wimpy for such things.

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In reply to: <Pine.LNX.4.10.10104182234370.678-100000@plp.plp.home.org>
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