Electronic – Is this a good layout for a 5A buck converter

dc/dc converterpcbpcb-designswitch-mode-power-supply

I have updated this question with the suggestions in comments and answers. Make sure you read everything.

I want to make a PCB for a switching regulator (buck converter). It's a TL5001-based regulator, but this doesn't really matter since the layout is about the power stage, which is common to any regulator of this type.

Here's what I got so far:

enter image description here

The basic idea is to make a star ground. The center of the star is the connector on the right, which is the output connector.
I tried to keep traces away from the inductor (it's a toroid but I'm not sure how it affects nearby traces.
C7 is the input capacitor, placed near the MOSFET, to provide enough current during switching.
The small components (C8/R10 and C9/R12) are snubbers for the catch diode and MOSFET. Previous experiences with this circuit have shown I need a snubber, or else I get a ringing about 15MHz. 10nf+56R solves this. The datasheet only talks about a snubber at the diode, not the MOSFET.

There is no trace between the coil and the diode (thin yellow line) because I couldn't find a way to run a low-impedance trace there, so I'll just solder a thick piece of wire in place.

The rest of the circuit is the PWM controller (TL5001) and the MOSFET driver (2N2222/2N2907).

The feedback pin of the IC is not connected, but it's a solder pad (LSP1 on the left) because I would prefer to run a remote sense wire.

Traces will be rounded once i get a more definitive layout, to reduce EMI (I don't know if that's even necessary)

As you can see, the board is also single-layer, as I don't have the capability to do double layer boards at home, so ground plane layer is out of the question

I would prefer answers to stick to the topic here which is the LAYOUT of the board. I'm not interested in answers regarding:

  • The converter IC: Yes, I know there are better ones that are faster, cheaper, and every other adjective you can throw at it. But I have a few TL5001s.
  • The MOSFET driver: Yes, i know there are dedicated MOSFET drivers. But this pair of 2222/2907 does the job I need.
  • Double layer boards: as I said before I don't have the capability to do double-layer at home.
  • "But you can have them made for cheap!": Yes, I know. I also know I could just buy a converter, and even save myself the headaches. But I CAN'T have boards made (3 month delays at the post and import restrictions).
  • Anything unrelated to layout of the board.

EDIT:

Here's a schematic. Vout for me is variable 2-12V, Iout is 0-5A.

enter image description here

EDIT 2:

Here's the schematic corresponding to the layout. There are minimal component changes (addd R13, R14 for slew rate limit, R12, C9 for snubbing mosfet).

enter image description here

Edit 3:

This is the final board I built:

enter image description here

Picture of the finished board:

enter image description here

And here's a video of it in action: http://youtu.be/NXNk-duzGrI

Best Answer

Many switched regulators include example layouts, such as the suggested alternative part TPS40200. http://www.ti.com/lit/ds/symlink/tps40200.pdf . The datasheet shows the evaluation module layout and a suggested layout. If you copy that layout then your circuit will probably work.

One thing I found interesting is that switched regulator layouts tend to use copper fills instead of traces to connect high-current paths and simultaneously provide some heat sinking. For example in your layout C10-C12 and the large rectangular component could sit on top of a solid rectangle of copper. Keep in mind that the electrons will take the lowest impedance path.

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