[Arm-netbook] LCD LED driver IC recommendation

[luke.leighton]

On Thu, Jan 10, 2013 at 2:49 PM, jm <joem at martindale-electric.co.uk> wrote:
> 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 looove 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.

 yes.

> That taxes the CPU a little however insignificant that might be.

 ah no it doesn't - these embedded controllers have PWM drivers
built-in, you upload (once) to a memory register what frequency and
duty cycle you want the PWM to operate at, and let it get on with it.

> A software crash will result in either a fully on or fully off
> screen I assume.

 well, a software crash would leave any PWM BL IC in either an on or
off state, so it's no odds.  actually, a software crash on a
CPU-controlled PWM would probably shut it down.

 those PWM backlight ICs are really there for systems which don't have
hardware-level PWM.

 i did choose the STM32F for a good reason :)

l.