At 09:38 PM 2/6/2013, Josh Koffman wrote: >I've been wondering about this too, but I'm having trouble finding >convertors that will efficiently supply the kind of current that I >think I need (at this point anyways). It's deceptive, many of the >datasheets tout efficiencies so high you start to think "well, who >cares about that 6% I'm losing". The current limits tend to be a >killer though. I did find a Linear chip here: >http://www.linear.com/product/LTC3534 that could work. It'll do 500mA >which should be enough to drive the two PSoC chips and the headphone >amp. In theory the headphone amp can run off less than 5V, but I'm >worried about what would happen if the output of the PSoC ends up >greater than the Vdd of the amp. I've got a couple of things for you to consider. 1) The LM2623 can generate +5V at better than an Amp if fed from 3-=20 "AA" cells. Its probably good for close to an Amp if fed from 2-=20 "AA" cells. The internal switch is rated at something like 2.2A and=20 I can testify that they do significantly better than that. 2) There are some really nice buck-boost converters out=20 there. Pololu has some nice modules already built up - you simply=20 treat them as a 3-terminal regulator. Have a look at=20 - they charge less than=20 $5 for a fixed 5V @ 500mA output from an input voltage of 1.5V=20 through 12V. Another buck more ($6) gets you 5V @ 500mA when=20 stepping UP, an Amp if stepping DOWN. Even if you decided that you=20 wanted to incorporate the switcher right on your PCB, it would be=20 worth getting a couple of these for prototyping and bread-boarding purposes= .. And - Pololu ships FAST. > > I should mention that one of these projects works with mic audio > > (Broadcast Quality) from a headset-worn electret microphone. I did > > wind up filtering the microphone bias supply with a simple > > capacitance multiplier circuit (NPN transistor configured as an > > emitter-follower, voltage divider from C- B- Gnd, large C from B to > > Gnd). PSU noise is buried in the noise floor. > >What would the effective capacitance value be? You know, I don't have the faintest idea. But its just an=20 emitter-follower with a voltage divider and bypass cap feeding the=20 base. That description of 'Capacitance Multiplier' dates back to my=20 early days in electronics - that was the description given in the=20 print publications that I was reading at the time and the name just=20 stuck. But - as a rough guess, it would be the capacitor on the base=20 * hfe which I would guestimate at 200 or so. I can go back and look at that project if you want component values -=20 I simply don't recall the specifics right now. dwayne --=20 Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax www.trinity-electronics.com Custom Electronics Design and Manufacturing --=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 .