I know that 3.3 ( or even 2.8 ) volt parts are becoming the norm, but a small DC to DC breakout board based on an Analog Devices, National, TI, or other chip would be nice. I could then run my 5v projects from two AA cells. It could be built to look like an 8 (or 14) pin DIP chip, which could be plugged into a socket on the project board.
I just use the tiny encapsulated PCB switching supplies like those from V-infinity for that.
Thanks for the info, they look like they could fit my requirements. The 73% efficiency isn’t too bad. The specs say that the output is unregulated. Has that been a problem? A 5v unregulated wall-wart means greater than 5v typically. Have you tried using them to drive a PIC (or other microcontroller) and an LCD?
Don’t try to run ICs and other logic from an unregulated supply.
What power rating were you looking at? They have unregulated and regulated versions of the devices (I don’t remember ever seeing one type with only unregulated and no regulated ersions). I usually use the smallest size.
I use the single-output 1W regulated encapsulated PCB. Beyond that, it’s a power application and I use unregulated power.
http://www.v-infinity.com/catfeatures.a … ky2=879492
But, I was looking through their products, and I only saw one device specifically designed for upconversions:
http://www.v-infinity.com/adtemplate.as … subcatky3=
It is a point-of-load converter that can up convert 3.3V to 5V (rather than something like 4.75-5.5V to 5V). It doesn’t have a Digi-key icon though…kind of sucks since that means you have to maybe order from them or get Digi-key to special order it for you. A lot of the small and medium converters I use are normally carried by Digikey.
If you can only find unregulated, then you could always convert 3V (from two cells) to an unregulated 6V or something slightly higher than 5V (if that is the voltage you are trying to get), and then run that 6V through a LDO to clamp it down to a regulated 5V.
Usually it’s much easier (and cheaper) to just add 2 more cells in series to provide that voltage. It’s more efficient too because current draw from a battery shortens it’s capacity in a non-linear fashion. If you double the current draw from batteries, you shorten the capacity by MORE than half. If you triple current draw, you shorten capacity by more than 1/3 and by a ratiometrically larger amount than when you were just doubling the current. So the higher current draw is, prgessively smaller increases in current are need to be to shorten battery life by the same amount.
Most DC conversions are down-conversions because of this. I normally only use switchers to convert things like 24V to 5V because an LDOs dissipate the excess voltage off as heat. No LDOs that I have seen can even dissipate this much heat from such a large voltage difference in the first place, so I couldn’t use them in situations like these even if I wanted to. I tend to use switching regulators to do such large down-conversions because they do it much more efficiently, but they cost more. As a result if I need 3.3V and 5V for a single circuit from a 24V battery, I use one switching supply to efficiently do a large down-conversion to something like 7V (a voltage slightly higher than the largest regulated voltage I need). Then I run this 7V through a 3.3V LDO and 5V LDO. THis lets me use only one expensive switching supply instead of two while maintaining efficiency.
If i need just 5V from a 24V battery, I obviously try to find one switching supply that will do it all in one step.
If you need less than 200 mA, try C&D NKE305DC or NKE305SC
http://www.cd4power.com/data/power/ncl/kdc_nkec.pdf
mouser has them in stock.