This reference design from Maxim is a current controlled boost driver designed for long strings of LEDs. Driving many LEDs in series has advantages over driving them in parallel. In a parallel configuration each LED will need it’s own current limiting resistor or current control, while the series LEDs make use of a single current controlled power supply. The driver must support the combined voltage of all the LEDs in the string. The reference design can supply up to 100 volts, which translates to around 30 LEDs.
. . . I’ve seen plenty of current controllers, but never one with a built in boost converter. You never know when something like this could come in handy! Certainly useful for when you already have lower supply rails in the system and you’d like to add a slew of LED’s to throw some serious light ;-)
MAX1561/MAX1599 is a slightly cheaper alternative that can put out 1.0 A of power! I shipped a commercial product with about 170 LEDs driven from standard USB power using the MAX1561. The package is a bit of a nightmare for DIY, though.
Nice. I imagine the DFN is about the same as a QFN (in terms of soldering difficulty). It took me an extra try on the first one, but after that they only take a little longer than a fine pitch QFP. Having hot air is really helpful with the exposed pad of the QFN/DFN’s though.