CS52015-3GDP3 Cherry Semiconductor Corporation, CS52015-3GDP3 Datasheet - Page 5

• Manufacturer Part Number: CS52015-3GDP3
• Description: 1.5A/ 3.3V Fixed Linear Regulator
• Manufacturer: Cherry Semiconductor Corporation

Figure 2: Conductor parasitic resistance effects can be minimized with
the above grounding scheme for fixed output regulators.
The CS52015-3 linear regulator includes thermal 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.
The case is connected to V
trical isolation may be required for some applications.
Thermal compound should always be used with high cur-
rent regulators 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
P
V
Calculating Power Dissipation and Heat Sink Requirements
IN(max)
OUT(min)
IN
D(max)
={V
is the maximum input voltage,
is the minimum output voltage,
IN(max)
V
IN
CS52015-3
T
ÐV
J
= T
OUT(min)
D
A
(Watts)
+ P
V
OUT
OUT
D
}I
on the CS52015-3, and elec-
´ R
OUT(max)
QJA
J
R
(¡C)
A
C
+V
(¡C)
conductor
parasitic resistance
Applications Information: continued
IN(max)
QJA
(C/W)
I
Q
R
LOAD
(1)
(2)
5
I
I
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
such as the CS52015-3 the majority of the heat is generated
in the power transistor section. The value for R
depends on the heat sink type, while R
tors such as package type, heat sink interface (is an insula-
tor and thermal grease used?), and the contact area
between the heat sink and the package. Once these calcula-
tions are complete, the maximum permissible value of
R
For further discussion on heat sink selection, see applica-
tion note ÒThermal Management for Linear Regulators.Ó
result can be substituted in equation (1).
OUT(max)
Q
QJA
is the maximum quiescent current at I
R
QSA
can be calculated and the proper heat sink selected.
(¡C/W)
is the maximum output current, for the application
QJA
QJC
, the total thermal resistance between the
QJA
R
is 3.5ûC/W. For a high current regulator
QJA
is calculated using equation (3) and the
= R
QJC
+ R
QCS
+ R
QCS
OUT
QSA
depends on fac-
(max).
QJC
QCS
QSA
(¡C/W)
(¡C/W)
(3)