Cheap "jellybean" buck regulator - Page 1
Forum section: electronics / projects

author: LukeW
author_rank: Frequent Contributor
timestamp: May 08, 2015, 08:18:18 am
content: What would you recommend as a general-purpose, moderately low-power, low-cost regulator IC operating in a buck (or other step-down) topology?Traditionally I'd use an abundant and cheap MC34063, but are there any better, more modern replacements that retain its low cost?Typical use-case I'd be looking at: Vi=24V, Vo=5V, Io=500mA.Being able to take the output current higher than that (say an amp, or two), and the input voltage higher than that (say somewhere 36-50V) would be nice but not critical.Availability from the major Western distributors in small quantities is a plus, as is minimal size of external components, BOM cost and ease of inductor/diode/etc selection.

author: mariush
author_rank: Super Contributor
timestamp: May 08, 2015, 08:57:18 am
content: Have a look at MCP16301, not quite cheap as a jellybean but you're saving money as you can go with smaller inductors and ceramic capacitors instead of large electrolytics:http://uk.farnell.com/microchip/mcp16301t-i-chy/ic-dc-dc-converter/dp/2445581(600mA max)MCP16312 seems worth a look as well :http://uk.farnell.com/microchip/mcp16312-e-ms/dc-dc-switching-reg-buck-500khz/dp/2414135(up to 1A)AP5004 is cheaper and also works, but as it works at lower frequencies there's tradeoff in component sizes :http://uk.farnell.com/diodes-inc/ap5004sg-13/ic-buck-reg-so8/dp/1825352(up to 2.5A)

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: May 08, 2015, 09:02:46 am
content: The main thing about more modern regs is they run a much higher frequency so you can use cheap ceramic caps instead of electrolytics and small inductors.MCP16301 isn't bad but there are cheaper options - look at Richtek and Alpha Omega at Digikey.Choice reduces as you get to 24V in but still a few optionse.g. AOZ1280 ( which happens to have the same footprint as MCP16301)http://www.digikey.co.uk/product-detail/en/AOZ1280CI/785-1277-1-ND/2769845

author: ajb
author_rank: Super Contributor
timestamp: May 08, 2015, 03:24:15 pm
content: For higher input voltages, there's the LMR16006. It's more expensive than the other options, but still SOT6/600mA and takes up to 60V, and also same pinout as the MCP16301.

author: technix
author_rank: Super Contributor
timestamp: May 08, 2015, 04:09:37 pm
content: MC34063.Jellybean catch-all SMPS chip for any configuration for up to 1.5A, or with external switch transistor any current.

author: langwadt
author_rank: Super Contributor
timestamp: May 08, 2015, 04:25:09 pm
content: Quote from: technix on May 08, 2015, 04:09:37 pmbut it is ancient and dog slow so you'll need huge inductors and capacitorsin proto quantities it's hard to beat the price of something like this:http://www.ebay.co.uk/itm/261688896873

author: technix
author_rank: Super Contributor
timestamp: May 08, 2015, 04:30:55 pm
content: Quote from: langwadt on May 08, 2015, 04:25:09 pmIn China sellers vendors Shenzhen sells grab bags of 20 MC34063 at US$1. Try beat this.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: May 08, 2015, 07:17:09 pm
content: Quote from: technix on May 08, 2015, 04:09:37 pmHas poor efficiency and needs big caps and inductors. A dinosaur.Costs saved on caps and inductors may more than offset parts cost diferences

author: paulie
author_rank: Frequent Contributor
timestamp: May 08, 2015, 07:37:27 pm
content: Only needs big cap and coil for high current. 10 for a dollar on Ebay. With cheap 2 cent inductor and penny diode has no competition for lowest cost. Can't be beat when high output, low noise, and efficiency are not that important. Oddly no cheap modules though.

author: codeboy2k
author_rank: Super Contributor
timestamp: May 09, 2015, 07:20:40 pm
content: 2 cent inductor? link please.EDIT: you're probably talking about axial leaded 1W inductors... I can see those at 3 cents maybe 2 cents each in large quantities of 100 or 200ebayEDIT2: I found these 50mA SMD 1812 inductors at qty 200 , which works out to 7 cents each.ebay

author: paulie
author_rank: Frequent Contributor
timestamp: May 09, 2015, 07:30:02 pm
content: Actually I misspoke. Should have said "ONE cent inductors" because that's what I paid earlier this year on aliexpress (always a dollar or so cheaper than ebay due to fees). But search there is a pain so here's a quick link for some 2 cent Ebay dealies:http://www.ebay.com/itm/281642082320?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AITIf you call couple hundered pcs of penny parts "large quantity" then maybe not taking this hobby seriously. I am worlds cheapest man but don't consider spending a buck or two more for a lifetime supply out of the question. I do get a kick out of the phrase "color wheel". Wondered for years until finding out it's the same as chinese word for "ring". LOLps. Aha... I see you have discovered the real world of global pricing. It's always a proud moment when Digi-key/Farnell fanboys emerge from their cocoon.

author: mariush
author_rank: Super Contributor
timestamp: May 09, 2015, 08:17:19 pm
content: While it may work for one-off or hobby projects, when it comes to mass produce something you might want to stick with using a distributor or a company that can guarantee delivery of the amount of parts you need, and the quality desired.What's the point of ordering 200 inductors off aliexpress or alibaba or ebay when next week the seller may no longer have the same inductor in stock, or they're mailing you a similar part and argue the specs are close enough to the other so they're interchangeable?I want to be able to select a part that I want and then also select a few alternate parts with the same footprint in case the one I really one can't be sourced or becomes expensive, and this is hard with sellers on aliexpress or whatever, you can't really be sure (one that i really want for the project and the rest as fallback/alternatives) with the same footprint and know II want to have access to the datasheet for parts and to have the peace of mind that the parts i buy now or next month will be genuine (and the same) and conforming to specs so I'm fine with paying a bit more for parts.With ICs like MC34063, yes, you can buy them from eBay for cheap but again, you don't know if they're genuine or they're just what left after some pcb assembly job was finished, or what was dropped by the chip shooters, or even worse maybe they're fakes made in some Chinese fab with minimal or no testing/quality control... or maybe they're recycled off things like ethernet hubs or switches.Buy a bit more expensive regulator IC but you reduce pcb space and use smaller parts like inductors and ceramic capacitors... or buy cheapest regulator IC and use whatever parts will work

author: technix
author_rank: Super Contributor
timestamp: May 10, 2015, 01:22:41 am
content: Quote from: paulie on May 09, 2015, 07:30:02 pmIn the homeland of Aliexpress I just buy all my parts from Taobao (the domestic version of Aliexpress) and those Mouser or Digikey prices, which can be several times more expensive, are largely ignored.Just for reference, my small stock of 1mH 1A inductors came at 5 U.S. cents each, grab bags of 20 at $1; $1 will also get you a few hundreds of 1N5819 Schottky rectifiers. PIC16F72 microcontrollers a are blown off at $0.25/each, I got a few ADR01B precision reference at $1.25/each, and used (aka already burnt in, less long term drift than new) LM399 precision Zener are sold at $2.5 a pop.

author: Rick Law
author_rank: Super Contributor
timestamp: May 10, 2015, 01:57:54 am
content: Quote from: LukeW on May 08, 2015, 08:18:18 amSince you want low cost, I suppose you don't mind the cheaper Chinese parts. How aboutXL1509 from XLSemi.3.3V, 5V, 12V and Adjustable version.Up to 2A (internal cut off at 2A)4.5V to 40V Input Voltage Rangehttp://www.xlsemi.com/datasheet/XL1509%20datasheet.pdfI first encountered the XL1509-ADJ when my B3603 failed. The B3603 is an LM2596 digital buck, but it uses the XL1509 to supplies the internal voltage running the controller.I blew the (low-current) inductor on the XL1509 by shorting the output. For a while, I was using my B3603 with an MC34063 powered buck for the unit's internal power supply. So I had an opportunity to compare the XL1509 head to head with the MC34063.I found the XL1509 has better line and load regulation, plus a better noise profile than the MC34063.Rick

author: kjs
author_rank: Regular Contributor
timestamp: May 10, 2015, 04:52:54 am
content: Quote from: blueskull on May 10, 2015, 04:17:55 am+1! These 1 to 2+MHz switchers are by far superior and at the end often cheaper and a lot smaller. Especially when noise is critical. I hate to place a bunch of L/C filters on a board to get rid of sub 200kHz spikes.

author: con-f-use
author_rank: Unknown
timestamp: May 10, 2015, 08:08:03 am
content: Quote from: mikeselectricstuff on May 08, 2015, 09:02:46 amI have ordered a few of these but I'm a bit puzzled by one figure in the datasheet. There C3 is connected to nothing and has no value. By reading a little more carefully I found that a 10n capacitor (presumably C3) is to be connected between BST and LX pins. If someone used the AOZ1280 in that way, can you confirm that?

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: May 10, 2015, 08:59:32 am
content: Quote from: con-f-use on May 10, 2015, 08:08:03 amYes - it's a charge-pump cap for the MOSFET gate driver - MCP16301 has the same

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: May 10, 2015, 09:02:11 am
content: Quote from: blueskull on May 10, 2015, 04:17:55 amYou can go high frequency without needing to use expensive parts from TI or very expensive from LT.Richtek and AOS are my usual first places to look.