-7,8V to -12V (MC34063)

Guest · **Posted:** Fri Feb 14, 2003 17:50

Hello!

I have the Sharp LM24014 Display!

The LCD needs -12V.
If I use the circuits with the MC34063 form http://www.skippari.net/lcd/t6963c_schem.html I get -7,8V.

Does anybody to wich value i must change the 5,6KOhm and 27kOhm to get -12V?

Thanks.

Bye
Wolfgang

Marty · **Posted:** Fri Feb 14, 2003 22:37

Are you going to try and actually make this? The charge pump device is quite exensive. There are other easier was to do this.

Your computer PSU has -12v for example. Or you could use the transformer idea http://www.skippari.net/phpBB2/viewtopic.php?t=19

Marty

Guest · **Posted:** Sat Feb 15, 2003 2:44

Marty wrote:

Are you going to try and actually make this? The charge pump device is quite exensive. There are other easier was to do this.

Your computer PSU has -12v for example. Or you could use the transformer idea http://www.skippari.net/phpBB2/viewtopic.php?t=19

Marty

I built it. The MC34063 is ca. 0,5â‚¬. But I found a solution. In this document: http://www.onsemi.com/pub/Collateral/MC34063A-D.PDF

I change the Rs by this formula |Vout| = 1.25 * ( 1+ R1/R2 ) to R1=127KOhm and R2=16,2KOhm.

And now the LCD works fine.

Bye
Wolfgang

Henri · **Posted:** Sat Feb 15, 2003 11:50

I'm glad that you already found the solution. I would have pointed you to that same formula. :wink:

GÃ¶tz · **Posted:** Thu Feb 27, 2003 12:01

Anonymous wrote:

And now the LCD works fine.

too late, but for others http://www.nomad.ee/micros/mc34063a/index.shtml
online design tool for mc34063 as step-up, step-down, or inverting
GÃ¶tz

Henri · **Posted:** Thu Feb 27, 2003 13:17

GÃ¶tz wrote:

http://www.nomad.ee/micros/mc34063a/index.shtml

Nice one. Thanks for the link GÃ¶tz.

LCDInfo.com

-7,8V to -12V (MC34063)

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