ML4818 Просмотр технического описания (PDF) - Fairchild Semiconductor

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производитель

ML4818

Phase Modulation/Soft Switching Controller

Fairchild Semiconductor 

ML4818

PRODUCT SPECIFICATION

Thermal Information

The ML4818 is offered in a Power DIP package. This pack-

age features improved thermal conduction through the lead-

frame. Much of the heat is conducted through the center 4

grounded leads. Thermal dissipation can be improved with

this package by using copper area on the board to function as

a heat sink. Increasing this area can reduce the θJA (see fig-

ures 14 and 15), increasing the power handling capability of

the package. Additional improvement may be obtained by

using an external heat sink (available from Staver).

Applications

The application circuit shown in Figure 16 features the

ML4818 in a primary-side controlled voltage mode

application with voltage feed-forward. Input voltage is

rectified 120VAC (nominal). Feed-forward is provided by

the RAMP pin via the resistor connected to the high voltage

input. Current is sensed through sense transformer T4.

0.555"

1

24

2

23

3

22

4

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20

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19

I

I

7

18

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17

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16

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15

I

I

11

14

12

13

Figure 14. PC Board Copper Area Used as a Heat Sink

50

40

30

20

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

I : HEAT SINK DIMENSION (INCHES)

Figure 15. θJA as a Function of I (see figure 15)

10

REV. 1.0.3 6/21/01

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