ML7818A(2005) Просмотр технического описания (PDF) - Micro Electronics

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производитель

ML7818A
(Rev.:2005)

3-TERMINAL POSITIVE VOLTAGE REGULATOR

Micro Electronics 

(3)

Heat Radiation Balance

The heat produced in the IC is radiated to ambience through the package and the heat

sink.

The quantity of the heat radiation depends on the heat source temperature, ambient

temperature and the thermal resistance of the package.

(3-1)

TO-220 with heat sink

Heat radiation balance model of the TO-220 with heat sink is shown as below.

PLOSS

θJC

θCH

θHS

Tj

Heat Source

(junction)

Temperature

θJS

Ta

Ambient

Temperature

Where

θjc :

θjs :

θCH :

θHS :

thermal resistance between IC chip (junction point) and the

package backside connecting to the heatsink.

thermal resistance between IC chip (junction point) and the

package surface.

thermal resistance between package backside and the heat sink

including the condidtion of insulator, silicon grease and

tighten torque.

thermal resistance of the heat sink

Resin

Chip

Package

Back Side

Package

Face Side

θJS

IC

θJC

θCH

θHS Heat Sink

If the js is large enough compare with other thermal resistance, the js can be neglected and the

heat radiation model can be mentioned as below.

PLOSS

θJC

θCH

θHS

Tj

Ta

The relation between temperature and heat radiation quantity is shown below.

Tj=PLOSS X (θjc+θCH +θHS) + Ta

(℃ )

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