cs5257a-1 ON Semiconductor, cs5257a-1 Datasheet - Page 9

• Manufacturer Part Number: cs5257a-1
• Description: 7.0 A Ldo 5?pin Adjustable Linear Regulator
• Manufacturer: ON Semiconductor

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 has a thermal
resistance which is measured in degrees per watt. Like series
electrical resistances, these thermal resistances are summed
to determine the total thermal resistance between the die
junction and the surrounding air, R
resistance is comprised of three components. These resistive
terms are measured from junction to case (R
sink (R
equation is:
A heat sink effectively increases the surface area of the
PD (max) + ( V IN(max) * V OUT(min) ) I OUT(max)
qCS
), and heat sink to ambient air (R
R QJA + R QJC ) R QCS ) R QSA
) V IN(max)
I IN(max)
qJA
. This total thermal
qJC
), case to heat
qSA
http://onsemi.com
). The
9
both the TO−220−5 and D
current regulator such as the CS5257A−1 the majority of
heat is generated in the power transistor section. The value
for R
depends on factors such as package type, heat sink interface
(is an insulator and thermal grease used?), and the contact
area between the heat sink and the package. Once these
calculations are complete, the maximum permissible value
of R
For further discussion on heat sink selection, see our
application note “Thermal Management,” document
number AND8036/D, available through the Literature
Distribution
http://www.onsemi.com.
The value for R
qJA
qSA
can be calculated and the proper heat sink selected.
depends on the heat sink type, while the R
Center
qJC
is 1.4°C/watt for the CS5257A−1 in
or
2
PAK−5 packages. For a high
via
our
website
qCS
at