Author Topic: Pcb Design Advice  (Read 327 times)

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Offline townie.au

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Pcb Design Advice
« on: July 28, 2021, 09:34:11 am »
Hi
So I've built a pcb using 2 x TPA3116D2. They both have the purpose made heatsink and the board functions great.
However the project requires me to make more space and am looking at redesigning the pcb to be much more compact.
What I would like to know is there a requirement to have large areas of copper tracks for such a amplifier?
I understand that these tracks would have less resistance to current and better conduction of heat transfer but I'm thinking the heatsink should be adequate enough on it's own. How small is too small for the pcb?
 

Offline Berni

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Re: Pcb Design Advice
« Reply #1 on: July 28, 2021, 09:51:53 am »
There is no hard line between this is thick enough and this is too thin and will blow up.

A thinner track just has more resistance, so it has more losses at a given current and gets hotter at a given current. At some point the losses can become so large that the track itself gets hot and starts heating near by components. But what is considered as a track getting too hot also varies wideley depending on the ambient temperature, how much heat the components can handle, how much heat the PCB can handle etc...

For currents under about 3A people tend to well overestimate how thick of a track they need, even a fairly wimpy thin looking track will handle that fine. But past that, then that the pesky square in the P=I^2*R starts to take over and the power loses really start growing quickly with each extra amp. Its at about 10A where you start needing big thick fills of copper. and at 20A the thicker 2 or 3 or 4 oz copper PCBs become sort of a must have.

With the sort of powers your amp runs at it probably doesn't need hugely thick copper, but its hard to say without a picture of what you find as thick. Audio amplifiers also have an advantage that they don't tend to output max power for very long in real world use cases, so they tend to run a lot cooler than what the worst case math predicts.
 

Offline tszaboo

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Re: Pcb Design Advice
« Reply #2 on: July 28, 2021, 10:05:16 am »
My rule of thumb: 50mm x 50mm can handle 5W in an internal ground plane.
So 4 layer board, regular copper thickness. And the heat path needs to be sufficient.
For this chip you have another option. Chose the package with the top thermal pad, and place a heatsink on the top.
Former username: NANDBlog
 

Offline townie.au

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Re: Pcb Design Advice
« Reply #3 on: July 28, 2021, 09:17:48 pm »
My rule of thumb: 50mm x 50mm can handle 5W in an internal ground plane.
So 4 layer board, regular copper thickness. And the heat path needs to be sufficient.
For this chip you have another option. Chose the package with the top thermal pad, and place a heatsink on the top.

Yep already have the ones with thermal pad on top and the correct heatsink.
I'll post pics of the original and redesigned layout to get the thoughts from you guys.
 


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