JLC PCB DC-DC Converter IC Recommendations Please - Page 1
Forum section: electronics / beginners

author: ssashton
author_rank: Frequent Contributor
timestamp: February 02, 2023, 03:19:32 pm
content: Hello Everyone!Short of it - can anyone recommend some nice DC-DC switching available on the JLC Parts library?https://jlcpcb.com/partsAlternatively maybe just from LCSC who have a larger range (but I'd have to pay extra to order them in) -https://www.lcsc.com/I'm designing a board that needs to step down 30V to 15V and supply 2A Max. To be honest 1A is probably enough, if that gives a better choice I'll check the load to be certain.I already built a prototype using the very common XL7015 (datasheet here) converter that is common on lots of Chinese products and is about $0.5 from JLC PCB assembly service.I've decided I'm not a big fan of this 'regulator' as the input has about 6mV noise but after the XL7015 it has increased to 12mV at @150KHz! That seems silly, and since this is an audio circuit I don't want extra noise if I can help it.I've used the MP2359 (datasheet here) in another project and it seems to work well with about 6mV noise (so not improving the input, but not making it worse) however that has a max input of 26V and this project needs to step down from 30V.I can see the MP2565 (datasheet here) that can handle 50V input but I don't know if it performs as well as the MP2359? I find it hard to compare the graphs between the documents.There is also the MP9486 (datasheet here) which can handle 100V input.Maybe MP4462? (datasheet here)Jesus there are so many!

author: CountChocula
author_rank: Unknown
timestamp: February 02, 2023, 03:45:00 pm
content: I don't have a recommendation on a chip, but I wanted to ask: did you filter the regulator output in your XL7015-based circuit? I think some noise is always going to come through if you're using a switching regulator, and so I thought I'd suggest adding a snubber LC circuit if you hadn't already thought about it (particularly since you already have a working circuit, which is not necessarily a given if you switch to another chip).—CC

author: ssashton
author_rank: Frequent Contributor
timestamp: February 02, 2023, 03:53:04 pm
content: It has the inductor and output capacitor that is part of the typical application circuit.I actually have another question (sorry!):Why would a person choose to run a switching regulator slower than it is capable of?I'm looking now at the MP4462 which is 4MHz capable, yet in the typical application circuits they are running it at 0.5MHz.

author: CountChocula
author_rank: Unknown
timestamp: February 02, 2023, 04:09:51 pm
content: Quote from: ssashton on February 02, 2023, 03:53:04 pmThose are the regular storage and smoothing elements of the circuits; I was speaking about adding an LC circuit on the output that helps reduce ripple and noise. I attached an example at the bottom from an LM2596-based buck design.Here's apaper from Rohmthat talks about it. You can find a bunch of docs about this topic, and it's been discussed before in the forums.QuoteOthers more knowledgeable can probably give you a better answer, but the switching frequency affects a bunch of characteristics, including efficiency, ripple, noise, etc. There's an interestingAN from TIthat talks about it.

author: langwadt
author_rank: Super Contributor
timestamp: February 02, 2023, 04:44:51 pm
content: Quote from: ssashton on February 02, 2023, 03:53:04 pmswitching losses likely to increase with frequency and there limit to how short an ON time you can get so at some loads in/out ratios you'll have start to skipping pulses

author: mariush
author_rank: Super Contributor
timestamp: February 02, 2023, 05:25:59 pm
content: I like MP9942 and it seems to be stocked relatively wellDigikey :https://www.digikey.com/en/products/detail/monolithic-power-systems-inc/mp9942agj-z/7361521JLCPCB :https://jlcpcb.com/partdetail/Monolithic_PowerSystems-MP9942GJZ/C11820930v is a bit close to the maximum supported - it says 4v to 30v input voltage, with tolerance for 36v transients, absolute maximum voltage 40v

author: samofab
author_rank: Regular Contributor
timestamp: February 02, 2023, 08:34:08 pm
content: I used MC34063AD which has an added benefit of being a "basic" part on JLCPCB assembly.Here's my implementation if it helps:https://github.com/samo4/Esp32PWP/blob/main/Boost.kicad_sch

author: mariush
author_rank: Super Contributor
timestamp: February 02, 2023, 11:29:16 pm
content: Quote from: samofab on February 02, 2023, 08:34:08 pmI don't think you can do 1A of current with the conditions he has : 30v in, 15v out , 1-2A current ... online calculators say less than 750mA would be doable. See for examplehttp://www.nomad.ee/micros/mc34063a/Plus, because it runs at <100 kHz , it would use big inductors and big capacitors.At that output current of 1-2A and reduction of voltage in half, I think 300-600kHz would make more sense.Some other ICs that may be goodAOZ1284 : SO-8 package, 36v in , up to 30v out, up to 4A, 200kHz to 2Mhz adjustable frequencyhttps://www.digikey.com/en/products/detail/alpha-omega-semiconductor-inc/AOZ1284PI/3973647https://jlcpcb.com/partdetail/Alpha_OmegaSemicon-AOZ1284PI/C48060lmr16030 : 60v in, up to 3A, 200kHz - 2.5 Mhz configurable etc etc (SDDAR - soft start version , PDDAR - power good version)https://www.digikey.com/en/products/detail/texas-instruments/LMR16030SDDAR/6098066https://jlcpcb.com/partdetail/TexasInstruments-LMR16030SDDAR/C136648https://jlcpcb.com/partdetail/TexasInstruments-LMR16030PDDAR/C90665rt8279 36v in, up to 5a output , up to 26v out, ~ 500kHzhttps://www.digikey.com/en/products/detail/richtek-usa-inc/RT8279GSP/4146427https://jlcpcb.com/partdetail/RichtekTech-RT8279GSP/C53194

author: ssashton
author_rank: Frequent Contributor
timestamp: February 03, 2023, 03:04:29 pm
content: Thanks for all your suggestions!The specs for MP9942 and MP4462 look very similar. Do you know if there is any performance advantage on the MP9942?

author: mariush
author_rank: Super Contributor
timestamp: February 03, 2023, 03:31:04 pm
content: MP4462 goes 36v , 3.5A, and it's configurable up to 4MhzMP9942 recommends max 30v in (but absolute max is 40v like the above) , up to 2A, and lower default fixed frequency of 410 kHzMP9942 is "synchronous, rectified, step-down, switch-mode converter", which means you don't need a schottky diode in the circuit, and has better integrated mosfets - lower Rds(on) - and the chip can be much more efficient if you select the right inductor and other components compared to MP4462You can see in pages 17-18 in both datasheets that even the recommended layout is quite different.