Voltage regulation circuit 12V to 5V in 5A range

[Demon]

Had to make the hole a Part, not included in Schematic, BOM or To Be Populated.

Discovered the Create From Selection / Create Array feature; real time saver to make grids of parts.




Starting to look 1/2 decent.

[Ioannis]

Wow! You did a lot of work!

I am pretty sure that the extra layers TI suggest are for less noise ad better heat dissipation. Have you checked how much extra cost is added by JLCPCB?

In general if you want/need to make the board smaller, you can move all componets to the left, connector closer to the inductor and the right board edge also moved to the left. I don't see why this pcb needs to be that large. Saves cost also I guess.

I'd add an extra output capacitor for less noise and better operation without much cost. Parallel capacitors make for lower ESR also.

Nice design. You become an KiCad expert!

Ioannis

[Demon]

EDIT:

At first I was tempted to make 2 prototypes; 2 layers and 4 layers; just to see if the extra cost is worth it. But the more I think about it, the more I'm leaning for the 4-layer design.

Two of the main objectives with this circuit is to reduce heat and stabilize the voltage (ripples). If the pros design their Eval board to that size with 4 layers, I can't really see why I should consider cutting corners.

But boy am I tempted.

[Demon]

...Have you checked how much extra cost is added by JLCPCB? ...

Not yet, I wanted to get as close to a "finalized design" before using JLCPCB's quote generator.

... I'd add an extra output capacitor for less noise and better operation without much cost. Parallel capacitors make for lower ESR also. ...

I didn't know that about the lower ESR.

EDIT the CAPS section

I just noticed the datasheet has a range of output capacitance at 5V from 25 to 100uF (table 4). So I just added 10uF and 1uF ceramics alongside the 47uF.

These guys have a nice bla-bla about "why there can be too much output capacitance on SMPS circuits":
https://www.cui.com/blog/understandi...citance-limits

... Nice design. You become an KiCad expert!

Ioannis

Thanks, but I can't really take credit for the design. I feel like Mr. Bean copying the test answers from the guy next to him. I really did put a lot of effort to do as close to what TI recommends.

As for "Kicad expert", that remains to be seen.

[Demon]

Well, if I'm going to have all that unused real-estate at the top, might as well do something with it:

- DC jack,
- power switch,
- multiple output headers,
- amp and volt test points.

It's all parts I have on hand, so it's not really costing me more. I don't see how it would disturb the cooling, since TI placed all the ventilation holes on the bottom section. It anything, it's extra cooling fins.




Now I just have to remember to slap a jumper on the amp test point for the circuit to work.

[Demon]

... Have you checked how much extra cost is added by JLCPCB? ...

Ioannis

4 layers with 2-1-1-2 ounces with assembly, the area of my circuit jumps from 63mm x 50mm up to 73mm x 70mm.

2oz $32.20
1oz $16.07

Another issue, I can't use Economy with 0201 SMD, i have to use Standard. I had to swap 0201 resistor and capacitor for 0402.


Final bill for 5 PCBs:
- PCB $55.45
- Assembly $83.89
- Total $165.21 (with UPS shipping), $33.04 each PCB.


Plan B:

1oz all layers

PCB $23.15
PCBA $67.92
Ship $ 25.87
Total $116.94, $23.39 each PCB.


Tempted to go with plan B. It's not like I'm going to push 5 amps, most likely 2.5A at best.

[Ioannis]

Ten dollars is quite enough. I'd select that 1oz too.

Maybe and more caps too.

Ioannis

[Demon]

I ordered 2 models:

- 4 layers, all 1 oz, 5 for $147 including shipping and duties, $29.40 each
- 2 layers, all 1 oz, 5 for $108 including shipping and duties, $21.60 each

I was able to stay on Economic price by avoiding 2oz layers, and remained at recommended area size by TI.

Output caps, 47uF (recommended), 10uF and 1uF.

I was tempted to add 0.1uF and 0.001uF but I thought I might be exaggerating. I can still add them in the final version if you guys think I should; I have room and it's not like they cost anything.

At least I'll have something to see how it ripples using PWM from transistors and mosfets.

I can also push it for heat test by PWMing a whole roll of LED strip.

[Demon]

I can get the price down a bit more by using another inductor:

Current: XAL1010-332MED by Coilcraft, $4.4191 x 5 = $22.10

Alternative: SRP1265A-3R3M by Bourns, $1.5387 x 5 = $7.70

That's a difference of $14.40 ($2.88/unit)


I didn't use the Bourns cause I'd have to order a minimum of 10 from Mouser, and that takes 8-15 lead days, and I wanted my PCB for testing yesterday.

There was 73 inductors in stock from Coilcraft, but that's already down to 38 (I only used 10 in my 2 orders).


Ioannis, have you had any experience ordering from Element or Onlinecomponents?

[Demon]

Once I get my order and done some testing, I'll be in a better position to know what configuration of layers I'm going to need.

I'm always getting emails from PCB assembly suppliers from alibaba, so I'll to make a RFQ for that "winning" configuration.

Just to see if I can get anything better than JLCPCB.

That'll also give me a chance to find a good competitor for my PCBs in the future. But I gotta admit, JLCPCB's online system is pretty slick once you get used to it.

[Ioannis]

Ioannis, have you had any experience ordering from Element or Onlinecomponents?

No. My country adds a lot of import taxes so I select suppliers within European Union or Mouser that ships tax free.

May main suppliers are Mouser, TME, SOSelectronics and local resellers for larger quantities.

Regarding the inductors, I think either Coilcraft or Burns (or other reputable brands) will make no difference, as long as you select one that has the specs.

At testing time you will see if adding more caps on output of the power supply makes any significant difference. Can't tell right now.

For mass production of assembled pcb JLCPCB may be more expensive. I usually do this for no more than 20-30 pcs, depending on the component count too. Greater production is cheaper for me if I do it locally and just order only the pcb's from JLCPCB.

Ioannis