CS5253-1GDPR5G ONSEMI [ON Semiconductor], CS5253-1GDPR5G Datasheet - Page 9

• Manufacturer Part Number: CS5253-1GDPR5G
• Description: 3.0 A LDO 5−Pin Adjustable Linear Regulator
• Manufacturer: ONSEMI [ON Semiconductor]

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.
Calculating Power Dissipation and Heat Sink
Requirements
operate at high junction temperatures. Therefore, it is
important to calculate the power dissipation and junction
temperatures accurately to ensure that an adequate heat sink
is used. Since the package tab is connected to V
CS5253−1, 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
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
High power regulators such as the CS5253−1 usually
The thermal characteristics of an IC depend on the
The maximum ambient temperature and the power
T J(max) + T A(max) ) PD (max)
R qJA
OUT
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on the
9
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
sink (R
equation is:
D
CS5253−1 the majority of heat is generated in the power
transistor section. The value for R
sink type, while the 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 selection, see our application note “Thermal
Management,” document number AND8036/D, available
through the Literature Distribution Center or via our website
at http://www.onsemi.com.
2
A heat sink effectively increases the surface area of the
The value for R
PAK−5 package. For a high current regulator such as the
PD (max) + ( V IN(max) * V OUT(min) ) I OUT(max)
qCS
), and heat sink to ambient air (R
R qJA + R qJC ) R qCS ) R qSA
) V IN(max)
qJC
is 2.5°C/watt for the CS5253−1 in the
qCS
depends on factors such as
I q
qJA
qSA
qJA
can be calculated and
depends on the heat
. This total thermal
qJC
), case to heat
qSA
). The