TA7818S 查看數據表（PDF） - Toshiba

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TA7818S

Three Terminal Positive Voltage Regulators

Toshiba 

TA7805,057,06,07,08,09,10,12,15,18,20,24S

(5) Installation of IC for power supply

For obtaining high reliability on the heat sink design of the regulator IC, it is generally required to

derate more than 20% of maximum junction temperature (Tj max).

Further, full consideration should be given to the installation of IC to the heat sink.

(a) Heat sink design

The thermal resistance of IC itself is required from the viewpoint of the design of elements, but

the thermal resistance from the IC package to the open air varies with the contact thermal

resistance.

Table 1 shows how much the value of the contact thermal resistance (θc + θs) is changed by

insulating sheet (mica) and heat sink grease.

Table 1

Package

TO-220NIS

Model No.

TA78××S

Torque

0.6 N·m

Mica

Not provided

Unit: °C/W

θc + θs

0.4~0.6 (1.0~1.5)

The figures given in parentheses denote the values at time of no grease.

The package of regulator IC serves as GND, therefore, usually use the value at time of “no

mica.”

(b) Silicone grease

When a circuit not exceeding maximum rating is designed, it is to be desired that the grease

should be used if possible. If it is required that the contact thermal resistance is reduced from

the viewpoint of the circuit design, it is recommended that the following methods be adopted.

Use YG6260 (TOSHIBA SILICON CORPORATION), if grease is used.

(c) Torque

When installing IC on a heat sink or the like, tighten the IC with the torque of less than the

rated value. If it is tightened with the torque in excess of the rated value, sometimes the

internal elements of the IC are adversely affected. Therefore, great care should be given to the

installing operation.

Further, if polycarbonate screws are used, the torque causes a change with the passage of time,

which may lessen the effect of radiation.

14

2003-01-29

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