NCV8501 Series
http://onsemi.com
13
HEATSINKS
A heatsink effectively increases the surface area of the
package to improve the flow of heat away from the IC and
into the surrounding air.
Each material in the heat flow path between the IC and the
outside environment will have a thermal resistance. Like
series electrical resistances, these resistances are summed to
determine the value of R
q
JA
:
R
qJA
+ R
qJC
) R
qCS
) R
qSA
(eq. 3)
where:
R
q
JC
= the junction−to−case thermal resistance,
R
q
CS
= the case−to−heatsink thermal resistance, and
R
q
SA
= the heatsink−to−ambient thermal resistance.
R
q
JC
appears in the package section of the data sheet. Like
R
q
JA
, it too is a function of package type. R
q
CS
and R
q
SA
are
functions of the package type, heatsink and the interface
between them. These values appear in heatsink data sheets
of heatsink manufacturers.
