[Arm-netbook] LCD LED driver IC recommendation

[jm]

On Wed, 2013-01-09 at 20:21 +0000, luke.leighton wrote:
> On Wed, Jan 9, 2013 at 11:01 AM, jm <joem at martindale-electric.co.uk> wrote:
> 
> > This link shows a couple of chips that have various input and output
> > voltages and currents: http://tinyurl.com/bgbdsaq
> >
> 
> found one!  ahhh $0.20.... love it.  SY7201 SOT23-5:
>     http://item.taobao.com/item.htm?spm=a230r.1.10.2.wpwLD6&id=14798320846
> 
> > High frequency inductor based switch mode supplies have >80% efficiency
> > is probably what you need for battery based operation.
> 
>  yeah i think that SY7201 is... well, there's an inductor on the
> circuit, right? :)
> 
>  oooo ciircuits, niiice:
> 
>  ftp://relay.alkotel.ru/service/eBOOK/TB-723A/Diagrams/
> 
>  this was where i found the reference to SY7201.

hmmm....

the solution looks a bit crude.

I think what the diagram is trying to say is that a signal
PWM0 is varied by generating a pwm signal from the CPU to control
the backlight brightness of the LCDs.
That taxes the CPU a little however insignificant that might be.
A software crash will result in either a fully on or fully off
screen I assume.

A better chip might be the TLC5922 from the tinyurl link above.
It has a serial port to program in the brightness which will
then be taken care of by the chip without the need for the CPU to
intervene.

(Caveat: I am no expert on LCD back lights.)