Hi,

On my web page, I give a small example circuit of an inverting charge pump
that you could use to achieve ~-4V with more than enough current to bias
the LCD. Unfortunately, I do not show the 555 part in the circuit,just the
diodes and caps. All you need is ANY low to medium-current pulse source, in
addition to the diodes/caps shown on my page. You could even just pulse one
of the PIC pins and use that. The rate would not be critical for this app,
even 30Hz would be fine,as would anything up to about 50kHz.

See:

http://www.people.cornell.edu/pages/shb7/neatcir.html

It's the second circuit down,but the info from the one above it applies,too
(voltage doubling charge pump).

Sean


At 02:01 PM 9/23/99 +1000, you wrote:
>Come to think of it maybe the 555 idea is more 'within specs' of the LCD
>module. Where can I get an example of this configuration, the data sheets
>don't appear to include it.
>
>TIA
>
>Wesley Moore

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| Sean Breheny
| Amateur Radio Callsign: KA3YXM
| Electrical Engineering Student
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