On 15 April 2015 at 13:26, Lee Mulvogue wrote: > G'day all > Any suggestions on some cheap (~$2 max), SIMPLE (SOT, SOIC, MSOP etc) > buck/boosts for 3.3V and 5V? > Not the top choice by several measures but still useful is the Olde MC34063 or it's slightly more modern variants (eg NCV3065 NCP3065 and others)(Some of these replace the excessively hi Vref with a lower one more suited to current sense applications.)(None seem to upgrade the venerable internal switch, alas). It uses minimal components given its total flexibility, can implement any "normal" topology (boost, buck, buck boost 2 switch, buck-boost 1 switch invert, CUK, SEPIC, more ...). Low cost. Available in DIP, SOIC and maybe smaller. Notionally only operates at 100 kHz - can be run slightly higher - still in spec - just almost not on graph. Startup 3V claimed and a shade under in practice. Runs at slightly less than startup but not a consideration with LiIon (or shouldn't be). Output is a (nasty) non-saturating Darlington bipolar stage which keeps efficiency away from the dazzling heights of the very latest ICs - but works well enough in many cases. Has reasonable good drive capability so useful power levels often achievable with internal switch. Can easily [tm] drive an external MOSFET or MOSFETs if better drive wanted. Inbuilt hi side current sense (unusual and a nice tough) but Vdrop further cuts into efficiency. Driver has both ends available so can be used as high side, low side or in between two switches driver. More or less "just works" as well as any device will. Sample layouts in extended data sheets from several manufacturers. Note that literature may be dated 201x or 200x but this is usually because whoever decided to "update" it and took off the 199x or 198x dates. Despite its antiquity, sloth and several bad points it's still useful. I've used it to good effect with an external MOSFET switch and 2xbipolar & no glue gate driver. Better can be had. Cheaper probably not. Still useful Russell McMahon --=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 .