Author Topic: JLC PCB DC-DC Converter IC Recommendations Please  (Read 1514 times)

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Offline ssashtonTopic starter

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JLC PCB DC-DC Converter IC Recommendations Please
« on: February 02, 2023, 03:19:32 pm »
Hello Everyone!

Short of it - can anyone recommend some nice DC-DC switching available on the JLC Parts library? https://jlcpcb.com/parts

Alternatively 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!
 

Offline CountChocula

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Re: JLC PCB DC-DC Converter IC Recommendations Please
« Reply #1 on: February 02, 2023, 03:45:00 pm »
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
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Offline ssashtonTopic starter

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Re: JLC PCB DC-DC Converter IC Recommendations Please
« Reply #2 on: February 02, 2023, 03:53:04 pm »
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.
 

Offline CountChocula

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Re: JLC PCB DC-DC Converter IC Recommendations Please
« Reply #3 on: February 02, 2023, 04:09:51 pm »
It has the inductor and output capacitor that is part of the typical application circuit.

Those 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 a paper from Rohm that talks about it. You can find a bunch of docs about this topic, and it's been discussed before in the forums.

Quote
I actually have another question (sorry!):

Why would a person choose to run a switching regulator slower than it is capable of?

Others 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 interesting AN from TI that talks about it.
Lab is where your DMM is.
 
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Online langwadt

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Re: JLC PCB DC-DC Converter IC Recommendations Please
« Reply #4 on: February 02, 2023, 04:44:51 pm »
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.

switching 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
 
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Online mariush

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Re: JLC PCB DC-DC Converter IC Recommendations Please
« Reply #5 on: February 02, 2023, 05:25:59 pm »
I like MP9942  and it seems to be stocked relatively well

Digikey : https://www.digikey.com/en/products/detail/monolithic-power-systems-inc/mp9942agj-z/7361521
JLCPCB : https://jlcpcb.com/partdetail/Monolithic_PowerSystems-MP9942GJZ/C118209

30v is a bit close to the maximum supported - it says 4v to 30v input voltage, with tolerance for 36v transients, absolute maximum voltage 40v

 

Offline samofab

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Re: JLC PCB DC-DC Converter IC Recommendations Please
« Reply #6 on: February 02, 2023, 08:34:08 pm »
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
« Last Edit: February 02, 2023, 08:36:12 pm by samofab »
 

Online mariush

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Re: JLC PCB DC-DC Converter IC Recommendations Please
« Reply #7 on: February 02, 2023, 11:29:16 pm »
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

I 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 example http://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 good

AOZ1284 : SO-8 package, 36v in ,  up to 30v out, up to 4A, 200kHz to 2Mhz adjustable frequency

https://www.digikey.com/en/products/detail/alpha-omega-semiconductor-inc/AOZ1284PI/3973647
https://jlcpcb.com/partdetail/Alpha_OmegaSemicon-AOZ1284PI/C48060

lmr16030 : 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/6098066
https://jlcpcb.com/partdetail/TexasInstruments-LMR16030SDDAR/C136648
https://jlcpcb.com/partdetail/TexasInstruments-LMR16030PDDAR/C90665

rt8279   36v in, up to 5a output , up to 26v out, ~ 500kHz
https://www.digikey.com/en/products/detail/richtek-usa-inc/RT8279GSP/4146427
https://jlcpcb.com/partdetail/RichtekTech-RT8279GSP/C53194

« Last Edit: February 02, 2023, 11:30:51 pm by mariush »
 

Offline ssashtonTopic starter

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Re: JLC PCB DC-DC Converter IC Recommendations Please
« Reply #8 on: February 03, 2023, 03:04:29 pm »
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?
 

Online mariush

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Re: JLC PCB DC-DC Converter IC Recommendations Please
« Reply #9 on: February 03, 2023, 03:31:04 pm »
MP4462 goes 36v , 3.5A, and it's configurable up to 4Mhz
MP9942 recommends max 30v in (but absolute max is 40v like the above) , up to 2A, and lower default  fixed frequency of 410 kHz
MP9942 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 MP4462

You can see in pages 17-18 in both datasheets that even the recommended layout is quite different.
 
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