How to calculate what heatsink to use.

[Exo]

How must one read the datasheet to calculate what heatsink to use?

For example, say i'm using a LM7805
https://www.electro-tech-online.com/custompdfs/2005/04/LM7512CPDF.pdf

And i'm inputting 17V and using a current of 0.5A
That would make 17 - 5 = 12V * 0.5A = 6W of dissipation.

Now, what factors and graphs in the datasheet should i use and how to see what kind of heatsink to use.

 

[David Bridgen]

The first two graphs on page 5, "Typical Performance Characteristics," of the data sheet are the ones to use.

With 6W dissipation a heatsink with a thermal resistance of no more than 10degC/W is necessary.

See **broken link removed** for a thorough treatise.

 

[Someone Electro]

whith that heat sink it wod heat up to 80 C° (at 20 C° sourundings)is its in a case or somting it cod heat up to 100 C°

meaby an 5 C°/W wod do by heating up only to 50 C° (or in a caseing up to 70C°)

 

[David Bridgen]

whith that heat sink it wod heat up to 80 C° (at 20 C° sourundings)is its in a case or somting it cod heat up to 100 C°

Yes.
No problem.

 

[Exo]

Thank you for your answer David.