On Wed, Sep 22, 2004 at 01:09:01PM +1200, Russell McMahon wrote:
> >I would like to drive a white LED for as long as possible at a roughly
> >constant current from the stored charge in a goldcap or other
> >large-value capacitor, eg 1F/5.5V.  It's for a one-off personal project.
> >
> >I've considered a few options: ...
> 
> What a nice specification of what you want and what you've looked at!

Thanks!

> Consider:
> 
> LTC3429  & friends
> Step up
> Single cell 0.85 - 4V in, 3v3 out (programmable)
> Up to 600 mA out !
> Good efficiency.

The LTC3429 looks pretty good, especially if I go with a higher-value
2.3V cap.  According to the data sheet it'll work right down to about
0.5V once it's running too.  And I think I can just about cope with
their TSOT package.

> LT are not usually the cheapest devices BUT they often provide superb 
> solutions.
> For one off projects their cost is often irrelevant.

The trick would be finding somewhere to buy them...  Linear's online
store do them at $2.31 each, but the cheapest shipping to the UK (by
FedEx) is $18.  :-(  No luck at Farnell or RS.

Chris
_______________________________________________
http://www.piclist.com
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist