On Tue, Feb 5, 2013 at 3:58 PM, Dwayne Reid wrote: > My suggestion is to drop the number of cells such that the maximum > battery voltage is LESS than your desired value, then use a boost > converter to get your desired voltage. I'm particularly fond of > Microchip's MCP1640 family - I've got a couple of projects that run > from 2 or 3 "AA" cells and I'm getting spectacular battery life. 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. > You mention in later posts that you are working with audio. Two of > the MCP1640 projects that I've done and a couple of others using > National Semiconductor's LM2623 are audio projects and I've had no > problems with switching noise. Good ground layout practices are a > must but I find it to be fairly easy to manage. > > If you do find that you are getting excessive noise on your Vdd line, > set your boost converter to be a little higher than desired, then use > a LDO to drop down to your desired voltage. But I haven't had to do > that on my projects. Based on my testing I'm starting to think I'll be fighting noise in the PSoC itself before I even start to hear PSU noise. I have to try to figure out why my UART is bleeding noise into the audio system at the moment. > 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? > Because some of my stuff is worn inside sports helmets, I've avoided > using any Lithium-based batteries. The helmet-mounted stuff uses 2- > prismatic NiMh cells with a pair of LM2623 boost converters (two > different supply voltages). Another project mounts inside a standard > Telex Ref Mic switch body (exactly what you see referees wearing in > Pro Sports on TV) - that one uses a pair of Duracell "AAA" > 'stay-charged' cells and a single boost converter. I could have use > a LiPo battery for that project but the enclosure form factor fit the > pair of "AAA" cylindrical cells perfectly. So that's what I used. > > I'm able to get away with relatively low-capacity batteries because > the high-current stuff is shut down until its needed. Cool! > I hope this helps. Absolutely, thank you! Josh --=20 A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools. -Douglas Adams --=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 .