CS5257A-1GDP5 Просмотр технического описания (PDF) - ON Semiconductor

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CS5257A-1GDP5

7.0 A LDO 5−Pin Adjustable Linear Regulator

ON Semiconductor 

CS5257A−1

PD(max) + (VIN(max) * VOUT(min))IOUT(max)

) VIN(max) IIN(max)

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 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, RqJA. This total thermal

resistance is comprised of three components. These resistive

terms are measured from junction to case (RqJC), case to heat

sink (RqCS), and heat sink to ambient air (RqSA). The

equation is:

RQJA + RQJC ) RQCS ) RQSA

The value for RqJC is 1.4°C/watt for the CS5257A−1 in

both the TO−220−5 and D2PAK−5 packages. For a high

current regulator such as the CS5257A−1 the majority of

heat is generated in the power transistor section. The value

for RqSA depends on the heat sink type, while the RqCS

depends on 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 RqJA can be calculated and 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.

http://onsemi.com

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