On 30 May 2013 00:57, Matt Callow wrote: > This plus an LDO may do the job. > > http://www.adafruit.com/products/390 > > (Although it's currently out of stock) > That cct is notionally ideal for solar use as it can implement a form of near MPPT tracking. by holding the panel at a deemed-optimum voltage. HOWEVER as they are using a linear panel load and not a smps this is a dream. That uses an MCP73871, which is in stock at Digikey. Datasheet - http://ww1.microchip.com/downloads/en/DeviceDoc/22090b.pdf Their circuit diagram - https://github.com/adafruit/USB-DC-Solar-Lithium-Ion-Polymer-charger/blob/m= aster/schem.png The "special magic" is in R2 & R3 which divide Vin and load it down until it puts 1.23V on the VPCC pin. In this case that sets Vin to 4.55V which they deem to be the optimum for quasi MPPT tracking. Note that they say that 1. They have spent a lot of time fiddling to get this circuit "just right"= : 2. It is now unavailable as they are redesigning it :-) Caveat Emptor maybe. Russell --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .