Question Trying to design voltage regulator PCB. Will this work?

[Rouslan]

I need voltage regulators for a portable Wii. There is a website, https://easyeda.com, that lets you design PCBs online and then order them cheaply. I designed something that looks like it could work, but I only have basic knowledge of electronics. Can someone more knowledgeable look at this and tell me if it would work?

I just took the "typical application" circuit from the TPS54428DDAR step-down converter, following the guide to get the wanted output voltages, and crammed four circuits onto one board.

Here is my schematic:

And here is my PCB design:

The blue lines are traces on the reverse side, connected by vias. It's hard to tell which ID corresponds to which component here, but the online editor already verified that the wiring matches the schematic. The big red squares are just exposed pads to solder onto. The traces are all 0.5mm thick, except the two in the middle, which are 0.8mm.

And here is a list of parts with links to datasheets:

Designator	Description	Part #
C1,C2,C4,C17	10uF ±10% 50V ceramic capacitor	GRM21BR61H106KE43L
C3,C7,C14,C20,C26	100nF ±10% 25V ceramic capacitor	GCM21BR11E104KA01L
C5,C15,C21,C27	1uF ±10% 50V ceramic capacitor	CL10A105KB8NNNC
C6,C10,C16,C22	8.2nF ±10% 50V ceramic capacitor	CL10B822KB8NNNC
C8,C9,C12,C13,C18,C19,C24,C25	22uF ±10% 25V ceramic capacitor	C1210C226K3RAC7800
L1	3.3uH ±20% 5A 38mΩ inductor	SRP5030T-3R3M
L2	2.2uH ±20% 5A 28mΩ inductor	YSPI0530-2R2M
L3,L4	1.5uH ±20% 7.5A 26mΩ inductor	MWSA0518S-1R5MT
R1	124kΩ ±1% 1/16W ±100ppm/℃ resistor	0402WGF1243TCE
R2,R4,R6,R8	22.1kΩ ±1% 1/16W ±100ppm/℃ resistor	0402WGF2212TCE
R3	11.1kΩ ±1% 0.1W resistor	RMC060311K1%N
R5	73.2kΩ ±1% 1/16W ±100ppm/℃ resistor	0402WGF7322TCE
R7	6.81kΩ ±1% 0.25W ±100ppm/℃ resistor	1206W4F6811T5E
U1,U2,U3,U4	Step-down converter	TPS54428DDAR

Some of the datasheets are partially or fully in Chinese. I figure only the one for the step-down converter is going to be looked at (which links to an English version), but I can search for English copies and update the links, if they are needed.

These parts were all chosen because they are available for their SMT service they offer (they will have the parts soldered for you, by machine). The editor's part selection tool is kind of a pain, so I'm aware there isn't any consistency with brands and some of the parts have higher voltage/current ratings than needed. Also I only noticed while making this post, L1 is unusually expensive compared to the other inductors. I will probably replace it with an equivalent one.

 

[Gman]

Printed Circuit Board Trace Width Tool | Advanced Circuits

Access Advanced Circuits' printed circuit board trace width tool. Includes information on how trace width is calculated.

www.4pcb.com

Use this trace width calculator to confirm the width is sufficient. It would be better if you can make the backside a full ground plane

 

[Rouslan]

Thanks. According to another thread, the Wii draws no more than 1.8A for any one voltage, which requires 0.338mm for external layers, so I'm good, except maybe for where the regulator sources connect to the 12V input. Is amperage linearly proportional to voltage? The total draw of the three voltages is 4A. If the amperage for the 12V traces is no more than 2A, then the traces are still more than thick enough. If it's 4A, I would need 1.02mm.

I'll make a new design later with the back mostly ground. I'll also put the step-down converters on the back so their center pads can attach directly to the rest of the ground (there will be little islands of non-copper surrounding the pins).

 

[jefflongo]

Thanks. According to another thread, the Wii draws no more than 1.8A for any one voltage, which requires 0.338mm for external layers, so I'm good, except maybe for where the regulator sources connect to the 12V input. Is amperage linearly proportional to voltage? The total draw of the three voltages is 4A. If the amperage for the 12V traces is no more than 2A, then the traces are still more than thick enough. If it's 4A, I would need 1.02mm.

I'll make a new design later with the back mostly ground. I'll also put the step-down converters on the back so their center pads can attach directly to the rest of the ground (there will be little islands of non-copper surrounding the pins).

You may want to keep all your components on the top side of the board, it makes it easier to assemble and sometimes easier to mount in a case. Typically your footprint will have vias connecting the center pad to the bottom ground plane. If you haven't fabbed your board already, you should go ahead and add the ground plane. It's very easy to do and will only simplify routing.

 

[Rouslan]

I made a new design:

This time not only is the back all ground, but ground now fills all the free space on the front. Several of the traces have been replaced with thick polygons. Also, although the image is bigger, the board is actually even smaller: it's 48mm x 37mm.

Unfortunately, it turns out that the assembly service for that website is only available for 1 oz copper thickness, which is too thin for the amperage I need (the traces would need to be thicker than the pins of the step-down converter can accommodate), and for 2 oz copper, the price of the PCB jumps from $5 to $20, which is reasonable, but I'm worried my design wont even work, so I'm going to shop around to see if anything cheaper is available. Alternatively, what I could do is have the traces exposed and manually thicken them with solder. I have to think about it.

Thanks for the tips.

 

[Ethan]

I would suggest sticking with 1oz copper as its more standardized, use a 4 layer design as well with 1oz to get more traces in the small space!