Please recommend a SMPS IC for 2 cell alkaline/nimh to produce fixed 3.3V >600mA - Page 1
Forum section: electronics / projects

author: alank2
author_rank: Super Contributor
timestamp: December 19, 2018, 12:39:53 am
content: Please recommend a SMPS IC for 2 cell alkaline/nimh to produce fixed 3.3V >600mA?Assuming two alkalines are depleted at 0.8V each (1.6V) I would think the minimum should be 1.6V or close to it.It doesn't have to be buck because two alkalines at 1.65V max each would be 3.3V.Not for many units, so price per piece isn't a huge concern. Minimized footprint would be a benefit. Only parts with leads that can be manually soldered.Current use probably will average 40-125mA, but it could surge to 450-500mA occasionally.I noticed the MCP1642.

author: nick_d
author_rank: Regular Contributor
timestamp: December 19, 2018, 04:35:29 am
content: Is the MCP1642 from Digikey/Mouser parametric search? If you have not used the parametric search, give it a try.I use Digikey and I have a specific procedure for doing it:1. Text search for keyword(s) or an example part.2. This takes me to the appropriate section of the catalog, with a reduced set of parameters or parameter values shown, corresponding to only those parts that match my search. This is important because there are many irrelevant parameters and weird one-off parts in each section.3. Select a couple of these parameters that more or less describe the text search you did, then remove the text search. This is so that, for example, suppose you searched for "op amp" originally, you will now see all products that are actually op-amps according to their parameters, rather than only those which happen to have "op amp" in their name.4. Choose "in stock" and possibly things like "RoHS" if you need. This really helps to cut down on crap obsolete parts.5. Enter the quantity you will be ordering, very important as it substantially affects price. I saw you gave this information.6. Now play with the parameters... the voltage and current ratings you need, the acceptable packages it can be in, etc.7. When things look stable and you have a screenful of likely looking candidates, click the up-arrow next to price and they will be shown in increasing order of price. Inspect carefully.8. I don't always pick the top item(s), maybe I just don't like them for some reason (manufacturer I've never heard of, wrong shape in the photo, etc) and I also scan down the column to see the best price/performance point, since I can over-spec the design slightly to win more margin sometimes.Since you have very comprehensive requirements this will take you to a small menu of options. You might want to read the datasheets of the top few choices and check pin count, power consumption, heat dissipation etc before selecting.By the way, searching "smps" will not give good results here. My impression is this would return mainly isolated devices (those that drive a transformer with optoisolator feedback), maybe try something like "switchmode boost regulator".cheers, Nick

author: alank2
author_rank: Super Contributor
timestamp: December 19, 2018, 04:39:34 am
content: Thanks Nick; yep I've been through the Digikey search. Wondering what others have used with success.

author: tautech
author_rank: Super Contributor
timestamp: December 19, 2018, 05:01:13 am
content: Quote from: alank2 on December 19, 2018, 12:39:53 amI've used MCP1640.Pay careful attention to PCB layout and inductors used, preferably use only from the recommended list.Some additional bulk capacitance on the output rail may be required to further suppress ripple....perfect for SMD tantalums.