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Cut heatsink tab off 7805

kickit2

Nov 20, 2011
14
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Nov 20, 2011
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14
Hey everyone.

I am putting together a circuit which draws only about 30ma from a 7805 (14v input). I'm trying to get everything as small as possible (without going smd) and I want the 7850 to lay flat. Issue is the heatsink tab turns this into a large footprint.

I'm am assuming that at 30ma the 7805 should do just find with its tab cut off. Can anyone confirm this?

It is not even getting warm with it on.

Kickit2
 

Raven Luni

Oct 15, 2011
798
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Oct 15, 2011
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798
At 14v there will be a bit of heat even with 30 mA draw. It is better to keep the tab and use the copper on the bottom of the board as a heatsink.
 

BobK

Jan 5, 2010
7,682
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Jan 5, 2010
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7,682
You can get a 78L05 in T092 if you want to save space.

Bob
 

GonzoEngineer

Dec 2, 2011
321
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Dec 2, 2011
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321
Just be careful how you cut it.......you can easily distor tit and fracture the die inside.
Don't ask me how I know!
 

Resqueline

Jul 31, 2009
2,848
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Jul 31, 2009
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I'm with Bob, with a mere 0.3W of dissipation a 78L05 is the way to go to save space.
 

OLIVE2222

Oct 2, 2011
690
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Oct 2, 2011
Messages
690
Yes the TO92 package can handle the 0.3W, but adding a zener diode at the regulator input can give a bit more headroom (without being too bulky).

Olivier
 
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