Need a buck switching power supply design

[zeke 693]

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?

 

[zeke 693]

I have used these Murata DC/DC converters in the past and they are simple and awesome. 

1. OKI-78SR-5/1.5-W36-C
2. OKI-78SR-3.3/1.5-W36-C

I think these are cool because they are a drop in replacement for typical 78xx linear regulators.

 

I just wished they put out a bit more current.

[veryalive 49]

Two in parallel?

[zeke 693]

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.  

[zeke 693]

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!

[spirilis 1,265]

Yeah was gonna say I know there are muRata modules that haul 10A or so. But probably around $10-$15 and that was a few years ago when I needed one.

[zeke 693]

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:

 

 

 

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

 

The LM43603PWPT pricing looks like this:  

 

 

 

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

 

 

 

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. 

 

 

 

[zeke 693]

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.

 

 

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

 

 

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

 

Cool!

[USWaterRockets 57]

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.

[RobG 1,892]

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.

 

[zeke 693]

Yeah, there we go. That's what I'm looking for!

 

Thanks @@RobG