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zeke

Need a buck switching power supply design

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Hi Everybody

 

I'm on the hunt for a bucking switch mode power supply design for my Marquee Clock.

 

Everything I've found so far is either crazy expensive to implement or just doesn't meet the operational parameters.

 

I'm hoping to find the following:

  1. Vin range = 12V to 25V
  2. Vout = 5V
  3. Iout = 4A
  4. Integrated Switch
  5. Cost <= $10 per IC

 

Have you seen anything like this?

 

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Well, well, well....

 

Lookie what I found here!

 

?1. OKL-T/6-W12N-C

  • 4.5V < Vin < 14V
  • 0.591V < Vout < 5.5V
  • Iout <= 6A
  • 30W

2. OKL-T/3-W12N-C

  • 4.5V < Vin < 14V
  • 0.591V < Vout < 5.5V
  • Iout <= 3A
  • 15W

And they are both surface mount.

 

Hmmm... I might have found what I'm looking for.  

:)

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Two in parallel?

 

 

I'm not sure that's safe. These regulators have something called PoL where they monitor the output and regulate based upon what they see.

 

I wouldn't want to see what happens when the two regulators start fighting each other. EEP!

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Yeah, those MuRata modules are pretty great in many respects except one. Their cost does not scale downwards when you buy in large quantities.

 

For example, the OKL-T/3-W12N-C pricing looks like this:

 

post-112-0-15230700-1461897437.png

 

 

But!  I managed to find a TI part that would scale down quite well in quantity.

 

The LM43603PWPT pricing looks like this:  

 

post-112-0-95115800-1461897461.png

 

 

And this is the simplified schematic. There's not too many parts there. Only the inductor will add significant cost to the BOM.

 

post-112-0-90465900-1461897323_thumb.png

 

 

These are the features that I like:

  • 3.5V < Vin < 36V
  • Vout (max) = 28V
  • Iout <= 3A
  • Step down regulator
  • Output = adjustable 
  • 16 pin TSSOP package

 

I have to redo the BOM cost analysis but I am seriously considering using this part over the MuRata part. 

 

 

 

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In addition to the 5V/3A switching regulator, I also require a 3.3V regulator. 

 

I was going to use a simple LP3869MP-3.3 LDO but it has only 0.5A capacity.

 

I stumbled across a webpage about the PMP9483 reference design. It combines one LM43603 regulator and two Nano modules.

 

So, I checked out these Nano modules and discovered that they are referring to the LMZ10501.

 

This device is cool because it can put out 1A.

 

post-112-0-97544900-1461898924_thumb.png

 

And it's price (in CAD) isn't too bad. Again, it scales well:

 

post-112-0-30286500-1461899033.png

 

So, it comes down to creating decent PCB footprints and integrating it all onto one board.

 

Cool!

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I've had good luck with the TI Nanomodules. I've used the LMZ21700 in a project to get 5V @ 650mA from a 4S LiPo battery.  I've been working on another design using the TPS81256.

 

I know these parts don't meet your exact requirements, but I'm just pointing out that I've been happy with the experience I have had with the TI nanomodules I've used so far. Take it for what that's worth.

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How about LM2576? They are super simple and dirt cheap (~$1.25 for all parts,) used them in few projects.

They are only 3A, but you could split your supply rail and use two of them.

 

post-73-0-10113000-1461977157.png

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