cs5205-1 ON Semiconductor, cs5205-1 Datasheet - Page 7

• Manufacturer Part Number: cs5205-1
• Description: 5.0 A Adjustable, And 3.3 V And 5.0 V Fixed Linear Regulators
• Manufacturer: ON Semiconductor

Calculating Power Dissipation and Heat Sink
Requirements
shutdown and current limit circuitry to protect the device.
High power regulators such as these usually operate at high
junction temperatures so it is important to calculate the
power dissipation and junction temperatures accurately to
ensure that an adequate heat sink is used.
electrical isolation may be required for some applications.
Thermal compound should always be used with high current
regulators such as these.
following four factors:
1. Maximum Ambient Temperature T
2. Power dissipation P
3. Maximum junction temperature T
4. Thermal resistance junction to ambient R
dissipation are determined by the design while the
maximum junction temperature and the thermal resistance
depend on the manufacturer and the package type.
P D(max) + { V IN(max) * V OUT(min) } I OUT(max) ) V IN(max) I Q
where:
application
†For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging
ORDERING INFORMATION
Specifications Brochure, BRD8011/D.
CS5205−1GT3
CS5205−1GDP3
CS5205−1GDPR3
CS5205−3GT3
CS5205−3GDP3
CS5205−3GDPR3
CS5205−5GT3
The CS5205−x series of linear regulators includes thermal
The case is connected to V
The thermal characteristics of an IC depend on the
These four are related by the equation
The maximum ambient temperature and the power
The maximum power dissipation for a regulator is:
V
V
I
I
Orderable Part Number
OUT(max)
Q
IN(max)
OUT(min)
is the maximum quiescent current at I
is the maximum input voltage,
is the minimum output voltage,
is the maximum output current, for the
T J + T A ) P D
D
(Watts)
5.0 A, 3.3 V Output
5.0 A, 3.3 V Output
5.0 A, 3.3 V Output
5.0 A, 5.0 V Output
5.0 A, Adj. Output
5.0 A, Adj. Output
5.0 A, Adj. Output
OUT
R QJA
Type
J
on the CS5205−x,
A
(°C)
(°C)
OUT(max)
qJA
(°C/W)
.
http://onsemi.com
(1)
(2)
TO−220−3, STRAIGHT
TO−220−3, STRAIGHT
TO−220−3, STRAIGHT
7
D
D
D
D
Package
2
2
2
2
package to improve the flow of heat away from the IC and
into the surrounding air.
outside environment has a thermal resistance. Like series
electrical resistances, these resistances are summed to
determine R
junction and the surrounding air.
1. Thermal Resistance of the junction to case, R
2. Thermal Resistance of the case to Heat Sink, R
3. Thermal Resistance of the Heat Sink to the ambient
result can be substituted in equation (1).
based on an average die size. For a high current regulator
such as the CS5205−x the majority of the heat is generated
in the power transistor section. The value for R
on the heat sink type, while R
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
the proper heat sink selected. For further discussion on heat
sink
Management,” document number AND8036/D, available
through the Literature Distribution Center or via our website
at http://onsemi.com.
PAK−3
PAK−3
PAK−3
PAK−3
A heat sink effectively increases the surface area of the
Each material in the heat flow path between the IC and the
These are connected by the equation:
The value for R
The value for R
(°C/W)
(°C/W)
air, R
selection,
qSA
R QJA + R QJC ) R QCS ) R QSA
qJA
(°C/W)
, the total thermal resistance between the
qJA
qJC
see
is calculated using equation (3) and the
is 3.5°C/W for a given package type
application
qCS
750 / Tape & Reel
750 / Tape & Reel
50 Units / Rail
50 Units / Rail
50 Units / Rail
50 Units / Rail
50 Units / Rail
depends on factors such as
qJA
Shipping
can be calculated and
note
†
qSA
“Thermal
qJC
depends
qCS
(3)