Question for The Pros, DC DC Switching Regulator - Page 1
Forum section: electronics / projects

author: TheRuler8510
author_rank: Regular Contributor
timestamp: April 08, 2014, 03:13:42 am
content: DC DC Switching Regulator, Question for The Pros. I am an RF guy, so I am all thumbs here.If I want to convert variable +2 to +4 volts (battery) on the input to a constant +3V out. What is the most cheap & efficient way? Low current is needed, i.e. <50 mA.Every data sheet I see is limited.Thanks in advance!

author: mariush
author_rank: Super Contributor
timestamp: April 08, 2014, 03:30:50 am
content: See an IC like LT1307 :http://www.linear.com/product/LT1307(Datasheet on the right)Example circuit for sepic mode on page 16 (center), lots of info and explanations in datasheet and you also can get this one in DIP package (though you won't get best efficiency on a breadboard).It's not the cheapest though. There are other that can work in SEPIC mode and do what you want.Alternatively, you can use a cheaper boost regulator and boost to about 3.3v then use a 100mA ldo to get it down to 3v. If battery gives more than 3.3v, the ldo will simply be less efficient.

author: David Hess
author_rank: Super Contributor
timestamp: April 08, 2014, 06:42:27 am
content: With such a low current requirement you can get away with a regulated buck boost charge pump.http://www.maximintegrated.com/datasheet/index.mvp/id/2154

author: digsys
author_rank: Unknown
timestamp: April 08, 2014, 07:16:26 am
content: Quote from: David Hessoooo nice chip !! I was going to suggest a MAX1044 or similar, but this suits the OP better !

author: Artlav
author_rank: Frequent Contributor
timestamp: April 08, 2014, 07:29:29 am
content: A charge pump regulator like MCP1252 should be perfect for the task.http://www.digikey.com/product-detail/en/MCP1252-ADJI%2FMS/MCP1252-ADJI%2FMS-ND/529832High efficiency, no start-up currents, few external parts and no inductors, 4-pin soic.MAX1759 that David Hess recommended seems to be of the same kind, but i haven't tried it.

author: jn
author_rank: Newbie
timestamp: April 08, 2014, 08:19:12 am
content: Hello, no idea what is your intention to use the regulator for. If switching noise is concern for you (could be with your background), charge pumps are not the best to pick. They tend to produce quite a lot of switching noise (obvious, from the principle of how they work).There are many small buck-boosts available around, e.g. LTC3129 (I used some time ago), or LTC3531-3, which could be exactly what you need. Another one we used before, is TPS63000. Unlike the LTCs, this one is not burst mode, so the output voltage is very smooth. Even though I don't like TI in general, this device worked very well for us. The TI runs quite high frequency, so even the inductor is pretty small. CISPR25 passed like charm.Cheers, J.

author: tautech
author_rank: Super Contributor
timestamp: April 08, 2014, 08:49:48 am
content: Have a look at Microchip MCP1640. SOT23/6 package. Have used it my stuff, got on to it a few years ago so might be getting dated by now.

author: TheRuler8510
author_rank: Regular Contributor
timestamp: April 09, 2014, 04:35:11 am
content: Guys,Thanks for the ideas; I'll be checking all these out.Tom

author: jeremy
author_rank: Super Contributor
timestamp: April 09, 2014, 05:16:14 am
content: and here is a similar one to the maxim from LT which I have used in lots of designs:http://www.linear.com/product/LTC3240

author: David Hess
author_rank: Super Contributor
timestamp: April 09, 2014, 05:30:14 am
content: I actually searched the Linear Technology parts first but using bipolar technology, they do not operate to as low a voltage for a given current output.

author: jeremy
author_rank: Super Contributor
timestamp: April 09, 2014, 05:31:34 am
content: nice! I didn't notice that. Will have to keep the maxim part in mind if my current requirements change.