CS5206-1GDPR3 Cherry Semiconductor Corporation, CS5206-1GDPR3 Datasheet - Page 6

• Manufacturer Part Number: CS5206-1GDPR3
• Description: 6A Adjustable/ and Fixed 3.3V and 5V Linear Regulators
• Manufacturer: Cherry Semiconductor Corporation

The CS5206 -X series of linear regulators includes thermal
shutdown and safe operating area circuitry to protect the
device. High power regulators such as these usually oper-
ate at high junction temperatures so it is important to cal-
culate the power dissipation and junction temperatures
accurately to ensure that an adequate heat sink is used.
The case is connected to V
isolation may be required for some applications. Thermal
compound should always be used with high current regu-
lators such as these.
The thermal characteristics of an IC depend on the follow-
ing four factors:
1. Maximum Ambient Temperature T
2. Power dissipation P
3. Maximum junction temperature T
4. Thermal resistance junction to ambient R
These four are related by the equation
The maximum ambient temperature and the power dissi-
pation are determined by the design while the maximum
junction temperature and the thermal resistance depend
on the manufacturer and the package type.
The maximum power dissipation for a regulator is:
where
V
V
I
I
P
OUT(max)
Q
Calculating Power Dissipation and Heat Sink Requirements
IN(max)
OUT(min)
D(max)
is the maximum quiescent current at I
={V
is the maximum input voltage,
is the maximum output current, for the application
is the minimum output voltage,
IN(max)
T
ÐV
J
= T
OUT(min)
D
A
(Watts)
+ P
OUT
D
}I
on the CS5206 -X, electrical
´ R
OUT(max)
QJA
J
(¡C)
A
+V
(¡C)
OUT
Applications Information: continued
IN(max)
QJA
(max).
(C/W)
I
Q
(1)
(2)
6
A heat sink 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 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 air,
These are connected by the equation:
The value for R
The value for R
a given package type based on an average die size. For a
high current regulator such as the CS5206 -X the majority
of the heat is generated in the power transistor section.
The value for R
R
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 per-
missible value of R
heat sink selected. For further discussion on heat sink
selection, see application note ÒThermal Management for
Linear Regulators.Ó
result can be substituted in equation (1).
QCS
R
QSA
depends on factors such as package type, heat sink
(¡C/W)
QJA
QJC
, the total thermal resistance between the
QJA
QSA
R
is normally quoted as a single figure for
QJA
is calculated using equation (3) and the
QJA
depends on the heat sink type, while
= R
can be calculated and the proper
QJC
+ R
QCS
+ R
QSA
QJC
QCS
(¡C/W)
(¡C/W)
(3)