Heat sink for a lm3886 amp

[whomeno]

ok
I'm looking at building an lm3886 amp. it will be a single supply at 24V. mono output.
Here are the schmatics



I'm going to use a laptop power supply at 24V 5A to power it.
I was reading on how to choose the right heat sink, but the math is above my head.
Could some one help me out on this one please?

[antonis]

Unfortunately, maths ARE needed for heatsinking..

So, either get them into your head or use a 10m² heatsink..

P.S.
It's extremely derogatory to call us for making 3 simple additions (θ_JC + θ_CS + θ_SA), isn't it..??

Anyway, pages 18-19 ..
https://www.ti.com/lit/ds/symlink/lm3886.pdf

[whomeno]

Not to be rude, Some of us can not do that type of math, Just like there is some things you are not good at.
I only ask as a small favor. I did not want an arm and leg

Thanks

[antonis]

https://www.amazon.in/Generic-Aluminum-Heatsink-LM3886-TDA7294/dp/B06WLNMKT5

https://www.aliexpress.com/item/1876564826.html

https://www.aliexpress.com/item/32998686478.html

https://www.diystompboxes.com/smfforum/index.php?topic=77993.0

[Ben N]

Those appear to be for a pair of LM3886, not one.

[whomeno]

Ben N, it is for 1 lm3886. I bought a pcb for it.
antonis, Thank you This helps alot

[Ben N]

I meant the ~150mm heatsinks linked by Antonis--they look to be for a stereo pair.

[whomeno]

Ben N, Sorry
Antonis, is right there are that big just for 1 lm3886.
The one i got i hadto get a tap and die to tap it.  150 x 69 x 37mm
It will just fit in the case

[antonis]

Most of commercialy availiable heatsinks are for "universal" use..
What counts is their "performance" (a mixutre of various parameters, like material thermal conductivity, dimensions, fin type, heat transfer coefficient, air flow rate, duct size and material colour..)

Their application is mainly depended on their thermal resistance, degrees Celsius per watt (°C/W), which is the "mechanical" equivalent of electrical resistance just to simplify thermal (heat flow) calculations..

So, it doesn't mind if we want to cool 1 LM386 (dissipating 50W) or 4 LM3886 (each one of them dissipating 12.5W) as long as our heatsink is adequate for the total amount of power dissipation..

[merlinb]

I was reading on how to choose the right heat sink, but the math is above my head.
Could some one help me out on this one please?

To be fair, the data sheet has been written in an extremely unhelpful way. Some of the most useful graphs are missing, and the formulas are wiritten on single lines! Yeesh.
Anyway, with a 25V supply and a 4 ohm load, my calculation comes out at 8 watts average dissipation.
You'll want something like a 1.6C/W heatsink, or lower. Look for a chunk of aluminium about 4 x 4 x 1 inch. A piece of U-channel about 7" long would also probably do.
It has thermal protection so even if you get it wrong, the chip will just switch off.