cs5205-2 ON Semiconductor, cs5205-2 Datasheet - Page 5

• Manufacturer Part Number: cs5205-2
• Description: 5.0 A, 1.5 V Fixed Linear Regulator
• Manufacturer: ON Semiconductor

Calculating Power Dissipation and Heat Sink
Requirements
operating area 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.
CS5205−2GT3
CS5205−2GDP3
CS5205−2GDPR3
The CS5205−2 includes thermal shutdown and safe
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, 1.5 V Output
5.0 A, 1.5 V Output
5.0 A, 1.5 V Output
OUT
R QJA
Type
J
on the CS5205−2,
A
( C)
( C)
OUT(max)
qJA
( C/W)
.
http://onsemi.com
(1)
(2)
CS5205−2
TO−220−3, STRAIGHT
5
D
D
Package
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).
regulator such as the CS5205−2 the majority of the heat is
generated in the power transistor section. The value for R
depends on the heat sink type, while R
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 application
note
AND8036/D, available through the Literature Distribution
Center or via our website at http://onsemi.com.
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
R
qJC
qJA
( C/W)
( C/W)
air, R
“Thermal
is 1.6 C/Watt for the CS5205−2. For a high current
can be calculated and the proper heat sink selected.
qSA
R QJA + R QJC ) R QCS ) R QSA
qJA
( C/W)
, the total thermal resistance between the
qJA
Management,”
is calculated using equation (3) and the
750 / Tape & Reel
50 Units / Rail
50 Units / Rail
Shipping
document
qCS
†
depends on
qJC
number
qCS
qSA
(3)