Lpc2000

I am liking the MC34063 idea, it's only $0.50 in 100qty, plus $0.85 for 
supporting components.  Add in a digital pot (i.e. MCP4021 - $0.70) in 
place of the R1 for the comparator circuit (which controls the voltage) and 
you can get a digitally adjustable contrast regulator (64 steps) for about 
$2.  In place of the digital pot you could always use an 8-bit latch (i.e. 
74HC373) with a variety of resistors, that would only be about $0.50 and 
give max 256 levels of control.  In either case, those look like pretty 
good solutions.

Thanks for your input!

-- Sean

At 04:49 PM 1/13/2006, you wrote:
>After messing with this one for years I finally went to Winstar and get
>mine on baord for free, however prior to that for digital control I used
>the MAX686, not a cheapest solution but solid, and not too expensive.
>The other cheap way might be to use an MC34063, they are only $1, but no
>digital control, or ON/OFF control without a bit of messing. I used an
>MC14051 ($0.38) and a variety of resistors to get numerous voltage steps.
>
>Cheers
>
>Al
>
>Sean wrote:
>
> >Sorry for the OT post, but I figure that since this is something common to
> >embedded projects you guys might have an elegant solution.
> >
> >I'm looking to create a contrast voltage (typ -13V 10mA) and a LCD Drive
> >voltage (min -23V 10mA), onboard I have +5V, +3.3V and Vin which is
> >typically +12V.  Ideally the contrast should be digitally controllable.
> >
> >The big part of the problem: it needs to be relatively cheap.
> >
> >I've been having a hard time trying to figure out the best way to do
> >this.  The best way that I can think of so far is going to be via voltage
> >multipliers.  I.e. take 3.3, invert and quadruple to get -13.2V for the
> >contrast, and then double again to get -26.4V for the LCD Drive.  I don't
> >know however if I can handle 10mA this way after octupling the voltage.
> >
> >I'm trying to stay away from switched regulators, as they can get expensive.
> >
> >Thanks for any suggestions that you may have.
> >
> >-- Sean
> >
> >
> >
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