On Tue, 17 Jul 2001 11:08:41 -0400, you wrote:

>Thanks everyone for the quick and informative responses!
>
>I am going to research both the split transformer solution and the 5-12
>voltage booster solution today.  $10 is too much for a switcher in this
>application. The budget is more like $4 or under.
=46or most small LCDs, you can often use a simple charge pump to boost
the 5V rail. If you can generate the drive waveform from the PIC (PWM
output or software toggle), the cost is just a  few diodes & caps -
pennies=20
>
>
>-----Original Message-----
>From: pic microcontroller discussion list =
[mailto:PICLIST@MITVMA.MIT.EDU]On
>Behalf Of Mark Newland
>Sent: Tuesday, July 17, 2001 10:09 AM
>To: PICLIST@MITVMA.MIT.EDU
>Subject: Re: [EE]:Voltage Reg vs Switcher
>
>Find a wall wart with a regulated 5V output and then use a boost =
convertor
>to
>get your LCD display voltage.
>
>"Robert E. Griffith" wrote:
>
>> I have a design that uses a 12v wall wart power supply because an LCD
>needs
>> the 12v.  The main circuit runs on 5v and 3v.  In the prototype I have=
 a
>5v
>> regulator (LM340TS) dropping the 12v to 5v and a 3v regulator =
(TPS7230QP)
>> that drops 5v down to 3v. This device will be on all the time.
>>
>> I have a heat sink on the 5v reg and it gets hot. I want to put the
>finished
>> circuit in a project box with vents but no fan.
>>
>> My question is: is there an easy, low cost, solution to implementing a
>> switcher to drop the 12v to 5v? Is this done? The 3v reg does not =
provide
>> much power so it is not a problem.
>
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