Lpc2000

Herbert Demmel wrote:

>Dear Sean,
>
>we had to deal with this issue on our unversal LCD controller boards - see 
>at www.demmel.com - and we solved it as follows: We took the (very cheap) 
>switcher IC TPS61041, which can produce up to + or -28 volts and made the 
>output voltage variable by feeding a PWM controlled voltage of 0...5 (can 
>be 0...3.3 volt as well) volt via an 100k resistor to the FB input. You 
>only need the TPS61041 which only costs about 1.5 US$ (single pieces) and a 
>ready to use Murata 10uH LQH32CN100K33L which costs less than 50 cent 
>(price is also for single pieces). You only need a few passive components 
>and a shottky diode like MBR0540T1 (about 40 cent) then and everything is 
>working fine. You get all parts at www.farnell.com, TI has good reference 
>schematics, you only have take care to use X7R capacitors. The TPS61041 can 
>be supplied with voltages between 1.8 and 6 volts.
>
>  
>
Interesting technique.  I also was thinking PWM followed by a filter, 
but I was thinking that you would need to switch the  output off/on.  
Your solution to modulate the FB line is a much cleaner one! Cool!

Regards,

TomW



-- 
Tom Walsh - WN3L - Embedded Systems Consultant
http://openhardware.net, http://cyberiansoftware.com
"Windows? No thanks, I have work to do..."
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