DC-DC Switching regulator, 12v -> 5v and 3.3v - Page 1
Forum section: electronics / projects

author: JaspaJami
author_rank: Contributor
timestamp: November 01, 2018, 03:22:49 pm
content: HelloIm looking for a switching dc-dc regulator. Input 12vdc, and two outputs: 5v and 3.3v. If it would be about 1000mA for 3.3v and 500mA for 5v that for sure should be enough. I think it can go quite much lower also from that. In i would like it to be as little extra components as possible. Any idea where i should try to find this kind of?At the moment best one is maybe TPS5438x:http://www.ti.com/lit/ds/symlink/tps54386.pdfBut that one needs quite a mount of extra components also.

author: t1d
author_rank: Super Contributor
timestamp: November 01, 2018, 03:41:06 pm
content: I did a quick search one Ebay and did not see a dual unit. But, I would think that something being designed for an Arduino, on a bread board, might be dual. Otherwise, use a pre-made converter to drop to 5v and add a small 3v3 circuit, to that... That would just be a 3.3v regulator and a couple of caps... Or two pre-made converters, 5v and 3v3. These buck converters are dirt cheap, on Ebay.

author: JaspaJami
author_rank: Contributor
timestamp: November 01, 2018, 03:53:28 pm
content: Trying to find good quality component that i can put on a production PCB. Amounts are not big ones so price is not so huge deal ( i mean if it cost 2€ or 6€, doesn't matter much)

author: mariush
author_rank: Super Contributor
timestamp: November 01, 2018, 04:14:21 pm
content: What's your budget?CheckMP2364:https://www.monolithicpower.com/pub/media/document/MP2364_r1.6.pdf1.4 Mhz switching frequency so you can use smaller inductors compared to that TPS chip, up to 1.5A per output, around 90% efficient etcIf you want really few components there's uModule parts from Linear, likeLTM4622with integrated inductors and everything... you just need a bunch of ceramic caps and resistors to set the output voltages ... but it's potentially pain in the ass BGA package and expensive (7$ in quantity):https://www.digikey.com/product-detail/en/linear-technology-analog-devices/LTM4622IY/LTM4622IY-ND/6181727Some other food for thoughtSuch a dual output chip as you can see will have around 90% efficiency ... so 3.3v at 1A = 3300mW and 5v at 0.5A = 2500mW , so 5800mW ...at 90% efficiency you're looking at ~ 6500mW power consumptionIf heat is not an issue, You could go for a cheaper 5v 1.5A+ switching regulator with higher efficiency and then use a LDO for 5v to 3.3v ... the LDO would obviously dissipate 1.7w of heat at 1A but that's doable in a big package... if it's MAX 1000mA , or if you have enough space then it's doable... and especially if it's for some arduino where you'd power from a 12v adapter and not batteries...So for example you could use a 0.5$ AP3513 IC which will still be at least 90% efficient at 2A output and at 5v 1.5A you're looking at 7500mW at 90%, or around 8300mW ... so really less than 2w extra... but the LDO only needs a ceramic capacitor on the output.For example, an AZ1084 is less than 0.5$:https://www.digikey.com/product-detail/en/diodes-incorporated/AZ1084CD-3.3TRG1/AZ1084CD-3.3TRG1DICT-ND/4505193

author: BFX
author_rank: Frequent Contributor
timestamp: November 01, 2018, 04:29:10 pm
content: If you need only quick solution try thishttps://www.ebay.com/itm/LM2596-4-Way-Multiple-Output-Switching-Power-Supply-Module-Board-3-3V-5V-12V-ADJ-/272914677919otherwise TI part you mentioned is better with little bit of effort to design an build custom solution.

author: mbest
author_rank: Contributor
timestamp: November 01, 2018, 04:43:35 pm
content: There are parametric searches on manufacturers sites, TI, Analog, Maxim, Monolithic, ROHM, etc. There are some with dedicated multiple output searches:https://www.analog.com/en/products/power-management/switching-regulators/step-down-buck-regulators/multiple-output-buck.htmlhttps://www.rohm.com/products/power-management/switching-regulators/multi-output-switching-regulatorsArticle about some multiple output options:https://www.digikey.ca/en/articles/techzone/2014/nov/generating-multiple-outputs-from-a-single-synchronous-buck-converter-is-simple

author: JaspaJami
author_rank: Contributor
timestamp: November 01, 2018, 06:50:39 pm
content: Quote from: mariush on November 01, 2018, 04:14:21 pmNot planned exactly but this whole device is going to be about 100€ in parts, and whole project where this is going is 25 000€. I personally dont care if power supply parts are 1€ or 10€. Easy to manufacture, reliability are important ones. And it need to survive vibrations.

author: JaspaJami
author_rank: Contributor
timestamp: November 01, 2018, 06:51:46 pm
content: Quote from: BFX on November 01, 2018, 04:29:10 pmOk for demo use, but now im looking best solution for the final product.

author: SiliconWizard
author_rank: Super Contributor
timestamp: November 01, 2018, 07:27:58 pm
content: LTC3622

author: mariush
author_rank: Super Contributor
timestamp: November 01, 2018, 08:17:53 pm
content: Yeah, so budget doesn't really seem to be a issue.How about pcb space, are you constrained in some ways? how about vertical height? How important is ease of repairability etc?Would it be more convenient to go with something that would allow for cheaper single layer pcbs?For example, you have DIP8 ICs likeSanken NR8887which would allow you to use through hole regulator, inductor and maybe a couple of electrolytic capacitors on top and then use surface mount ceramics on the bottom , or you could go completely through hole for both voltages.

author: thm_w
author_rank: Super Contributor
timestamp: November 02, 2018, 12:06:16 am
content: https://www.digikey.ca/product-detail/en/recom-power/R-78E3.3-1.0/945-2409-5-ND/5327711- 12V to 3.3V 1A $4https://www.digikey.ca/product-detail/en/recom-power/R-78E5.0-1.0/945-2201-ND/4930585- 12V to 5V 1A $4

author: technix
author_rank: Super Contributor
timestamp: November 02, 2018, 03:02:16 am
content: I have been using TPS563200 for a while. That is a single buck chip though, but very little additional components needed.

author: JaspaJami
author_rank: Contributor
timestamp: November 02, 2018, 12:33:28 pm
content: Quote from: mariush on November 01, 2018, 08:17:53 pmPCP space is not much of an issue but vertical height is. Lets say 10mm from the board starts to be near maximum.Repair... most likely if problems whole board will be changes (about half price from whole unit bacause display is easy to remove).PCB is going to be double sided, but thru hole is not problem at all. Anyway board is going to be combination of thru hole and smd:s

author: JaspaJami
author_rank: Contributor
timestamp: November 02, 2018, 12:36:10 pm
content: Quote from: thm_w on November 02, 2018, 12:06:16 amThese or this kind of could be interesting. Have to check that they are not too tall, but most likely not.EDIT: and seems to be similar not so high SMD modules:https://www.digikey.fi/product-detail/en/recom-power/R-78AA3.3-1.0SMD/945-1606-5-ND/2303054