CS5253B-1GDP5 ON Semiconductor, CS5253B-1GDP5 Datasheet - Page 9

• Manufacturer Part Number: CS5253B-1GDP5
• Description: IC REG LDO LIN 3A ADJ D2PAK-5
• Manufacturer: ON Semiconductor

Specifications of CS5253B-1GDP5

• Regulator Topology: Positive Adjustable
• Voltage - Output: 1.25 ~ 5 V
• Voltage - Input: Up to 13V
• Voltage - Dropout (typical): 1.05V @ 3A
• Number Of Regulators: 1
• Current - Output: 3A
• Current - Limit (min): 3.1A
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: TO-263-5, D²Pak (5 leads + Tab), TO-263BA
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: CS5253B-1GDP5OS

capacitance and the input voltage is instantaneously shorted
to ground, damage can occur. In this case, a diode connected
as shown in Figure 22 is recommended.
is required is to solve for current:
where:
typical short circuit current value provided in the
specifications, serious thought should be given to the use of
a protection diode.
Current Limit
under excessive load conditions.
Short Circuit Protection
clamps the output current at approximately 500 mA less than
its current limit value. This provides for a current foldback
function, which reduces power dissipation under a direct
shorted load.
Thermal Shutdown
activate above a die junction temperature of approximately
150°C and to shut down the regulator output. This circuitry
has 25°C of typical hysteresis, thereby allowing the
regulator to recover from a thermal fault automatically.
A rule of thumb useful in determining if a protection diode
I is the current flow out of the load capacitance when
C is the value of load capacitance
V is the output voltage, and
T is the time duration required for V
If the calculated current is greater than or equal to the
The internal current limit circuit limits the output current
The device includes short circuit protection circuitry that
The thermal shutdown circuitry is guaranteed by design to
V
from high to being shorted.
CONTROL
Figure 22. Diode Protection Circuit
is shorted,
V
V
CONTROL
POWER
CS5253B−1
I + C
Adjust
T
V
V
SENSE
V
OUT
CONTROL
to transition
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9
Calculating Power Dissipation and
Heatsink Requirements
operate at high junction temperatures. Therefore, it is
important to calculate the power dissipation and junction
temperatures accurately to ensure that an adequate heatsink
is used. Since the package tab is connected to V
CS5253B−1, electrical isolation may be required for some
applications. Also, as with all high power packages, thermal
compound in necessary to ensure proper heat flow. For
added safety, this high current LDO includes an internal
thermal shutdown circuit
following four factors: junction temperature, ambient
temperature, die power dissipation, and the thermal
resistance from the die junction to ambient air. The
maximum junction temperature can be determined by:
dissipation 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:
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
case−to−heatsink (R
(R
the D
the CS5253B−1 the majority of heat is generated in the
power transistor section. The value for R
heatsink type, while the R
package type, heatsink interface (is an insulator and thermal
grease used?), and the contact area between the heatsink and
the package. Once these calculations are complete, the
maximum permissible value of R
the proper heatsink selected. For further discussion on
heatsink selection, see our application note “Thermal
Management,” document number AND8036/D.
High power regulators such as the CS5253B−1 usually
The thermal characteristics of an IC depend on the
The maximum ambient temperature and the power
A heatsink effectively increases the surface area of the
The value for R
qSA
PD (max) + ( V IN(max) * V OUT(min) ) I OUT(max)
2
). The equation is:
PAK−5 package. For a high current regulator such as
T J(max) + T A(max) ) PD (max)
R qJA + R qJC ) R qCS ) R qSA
) V IN(max)
QJC
qCS
is 2.5°C/watt for the CS5253B−1 in
), and heatsink−to−ambient air
qCS
depends on factors such as
I IN(max)
qJA
qJA
can be calculated and
. This total thermal
qSA
R qJA
depends on the
OUT
on the
qJC
),