My tpa3118 board - comments/critiques?

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I run traces under inductors all the time, as long as you understand the implications of doing it and make sure it's mitigated or insignificant, it's fine.
...as long as you unterstand the implications...
That is the point. For a novice it is better advice not to route in the vicinity of inductors stray field. Specially in the case of unshielded inductors.
 
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Thank you doctormord.

If you go for this big/expensive inductors, stay also with MKP caps in the output filter. Of course, MLCC is mostly fine but they perform worse than MKP (MKT is okay to). I did extensive simulations on this aspect.

I think we can all agree this kind of design work is a game of managing compromises. One of my goals was to have a physically small board, and leaded film caps conflict with that goal (due to their size). I actually thought about dropping the big fancy inductors for something smaller (and cheaper), but after Gmarsh called them deliciously overkill I feel compelled to keep them. :)

Running traces under an inductor is normally a "no/don't". Even if the inductor is shielded and orientated like so, some amount is HF will couple into the trace.

I relaxed my small size goal a bit to fit the leaded film caps for the output filter, so I increased the board size a bit more to run those PVCC traces on the outside.

Are your screw holes on any grid dimension or do I need to drill four holes with a stencil?

Are you implying you're going to obtain one of these boards and do a build with it? Or was that a rhetorical "I"? If the former, I'm flattered; though I'm guessing it's the latter. ;) Anyway: I just threw the mounting holes on there without much thought, mostly as a reminder to actually add some mounting holes.

Fill up the outputs pin connections with copper to make them more solid.

I think I did this, if I understand you correctly.

The VIAs under the chip belongs to GND so they need solid connection to this potential.

Done (I think).

What about D1/C1/R11?

An filters for GVDD/AVDD should be as close to the chip as possible.

Not sure about D1/C1/R11.

And unless I'm mistaken about which components comprise filters for GVDD/AVDD, I think I'm about as close as I can get, short of moving to a smaller component size. (I want the TPA chip itself to be the only "hard" thing to solder. Everything else is 805 size or bigger, which I find a fairly comfortable size.) Actually, I can probably make things a little tighter, I just need to do a bit more research on manufacturing limitations. But I'm waiting to get the fundamental layout right before I start that kind of fine-tuning.

Thanks again!
 

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There are at least two pins on the input side that need to go to GND. I don't see them in post #22.

Good catch DUG! That's a tool unfamiliarity error on my part. I had many un-routed GND connections, but they were hidden. That, and I was also overlooking some status information in the GUI (that literally said "X not routed connections"). :eek:

Anyway, those are fixed, thank you!

Even though DUG's board was the inspiration for this board, Gmarsh's "Wiener" wins in the fun name category. ;) So to continue with that theme, I think I'm going to name this the "Little Smokie". Works on many levels I think. :rolleyes:

Too soon to be thinking about fun names?
 

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Actually, I live in Chicago, which is famous for hot dogs (and deep dish pizza of course). Within the city, there's a renown hot dog stand named "Hot Doug's" (now closed, unfortunately). So perhaps to honor diyAudio's DUG, and maintain the wiener theme, I should name this board "HOT DUG".

Still works on numerous levels I believe.
 
Actually, I live in Chicago, which is famous for hot dogs (and deep dish pizza of course). Within the city, there's a renown hot dog stand named "Hot Doug's" (now closed, unfortunately). So perhaps to honor diyAudio's DUG, and maintain the wiener theme, I should name this board "HOT DUG".

Still works on numerous levels I believe.
I like the name "HOT DOUG".

It's definitely a name that creates more questions than it answers. "What's a hot doug?"
 
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Thoughts on this? Should be mounting screw clearance now. I tightened the layout up a bit. Also did a Gerber rendering via ZofZ PCB program.
 

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There is no need for such big input caps. Voltage of these bulky things is far overrated - you do not need 100 or 250V here. And the physical size works like an antenna picking up noise.
There are much smaller film caps on the market: WIMA.
Besides that the layout looks fine to me
 
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My thoughts:

- I agree with voltwide, a 7.5x7.5mm film capacitor footprint should be the biggest that you need for the C2/C3 - you can get up to 3.3uF/63V film in that size. Making the caps smaller should free up room to label your inputs :)
- C20/C19 should be 5.5x7.5mm size minimum, big enough to fit 1.5uF for a 4 ohm load. 7.5x7.5 would be plenty. C16/C17 are typically 10nF, you don't need them to be that big.
- The exposed copper under the TPA: it looks like you just put a GND pad underneath there. Rather than doing that, draw a polygon on the BSTOP layer instead.
- I wouldn't put vias on top of pads like you're doing with R5/R6.
- The "VCC" and "SPEAKER" text are covered up by the terminal blocks when you mount them.
- Maybe change D1 to a vertically mounted footprint, one of the leads is awfully close to the screw hole.
 
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Thank you everyone for your continued feedback, I really appreciate it. Very helpful!

I agree with voltwide, a 7.5x7.5mm film capacitor footprint should be the biggest that you need for the C2/C3 - you can get up to 3.3uF/63V film in that size. Making the caps smaller should free up room to label your inputs :)

Ironically, if you go back to my first few versions of this board, I did have the smaller input caps. Later I thought it would be nice to give myself the option to use bigger caps. For example, I can't find any polypropylene film caps in the smaller footprint. (But by that same argument, what if I want to use those monster paper in oil caps?) Anyway, smaller caps it is! I'll "settle" for polyester. ;)

C20/C19 should be 5.5x7.5mm size minimum, big enough to fit 1.5uF for a 4 ohm load. 7.5x7.5 would be plenty. C16/C17 are typically 10nF, you don't need them to be that big.

Good catch, and most helpful for further optimizing space on the output side!

The exposed copper under the TPA: it looks like you just put a GND pad underneath there. Rather than doing that, draw a polygon on the BSTOP layer instead.

You pre-empted a question I was going to PM you on that particular issue. Thank you. :)

Maybe change D1 to a vertically mounted footprint, one of the leads is awfully close to the screw hole.

Yes, that was on my mental to-do list as well.

Board is now about 45x82.
 

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Minor updates: put the power and speaker out on the same board edge, and lengthened the board a bit to give the inputs a little more breathing room.

Thinking I might have it fabbed, any thoughts?
 

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looks like eagle cad to me. In that case, do not forget to execute DRC command to check your pcb. I discovered some clearance errors...

Indeed, Eagle CAD. I have used DRC, including the DRC rules from the fab house (Elecrow). I got a ton of "Dimension" errors around the inductor slot holes. But I actually got the inductor parts from Gmarsh, and he said they worked for Elecrow, so I think I'm good.

The only other errors I got were "Stop Mask", which if I understand what I read correctly, they should only be cosmetic.

Anyway, I went ahead and submitted to Elecrow. With shipping, it was just under $20 for 10 boards. I've wasted $20 on less meaningful endeavors before, so, I'm not too worried.

some minor beautifying tweaks:
move c2 to align with c3
mov dc-in/speaker out terminals to center in vertical direction

C2 and C3, good call, done. I got the dc/speaker terminals a little closer to center, but I was trying to maintain some symmetry on the output circuit (per doctormord's suggestion), so didn't want to move the speaker terminal too much.

So... we'll see! Assuming there are no deal-breaking board/circuit errors, the next big challenge will be soldering the actual tpa3118 chip, particularly the thermal pad. Solder probably gives the best thermal conductivity, but I wonder if thermal paste or thermal cement is "good enough"?

Thanks again everyone, I'll post pics of the boards when I receive them!
 

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