Rev. R 10/20

2

TOP242-250

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Section List

Functional Block Diagram ....................................................................................................................................... 3

Pin Functional Description ...................................................................................................................................... 4

TOPSwitch-GX Family Functional Description ....................................................................................................... 5

CONTROL (C) Pin Operation.................................................................................................................................... 6

Oscillator and Switching Frequency.......................................................................................................................... 6

Pulse Width Modulator and Maximum Duty Cycle .................................................................................................... 7

Light Load Frequency Reduction.............................................................................................................................. 7

Error Amplifier .......................................................................................................................................................... 7

On-Chip Current Limit with External Programmability ............................................................................................... 7

Line Undervoltage Detection (UV)............................................................................................................................. 8

Line Overvoltage Shutdown (OV).............................................................................................................................. 8

Line Feed-Forward with DC

MAX Reduction ................................................................................................................ 8

Remote ON/OFF and Synchronization...................................................................................................................... 9

Soft-Start ................................................................................................................................................................. 9

Shutdown/Auto-Restart ........................................................................................................................................... 9

Hysteretic Over-Temperature Protection ................................................................................................................... 9

Bandgap Reference ............................................................................................................................................... 10

High-Voltage Bias Current Source .......................................................................................................................... 10

Using Feature Pins ................................................................................................................................................... 10

FREQUENCY (F) Pin Operation .............................................................................................................................. 10

LINE-SENSE (L) Pin Operation ............................................................................................................................... 10

EXTERNAL CURRENT LIMIT (X) Pin Operation....................................................................................................... 11

MULTI-FUNCTION (M) Pin Operation...................................................................................................................... 11

Typical Uses of FREQUENCY (F) Pin ...................................................................................................................... 14

Typical Uses of LINE-SENSE (L) and EXTERNAL CURRENT LIMIT (X) Pins ....................................................... 15

Typical Uses of MULTI-FUNCTION (M) Pin ........................................................................................................... 17

Application Examples .............................................................................................................................................. 20

A High Efficiency, 30 W, Universal Input Power Supply ........................................................................................... 20

A High Efficiency, Enclosed, 70 W, Universal Adapter Supply ................................................................................. 20

A High Efficiency, 250 W, 250-380 VDC Input Power Supply.................................................................................. 22

Multiple Output, 60 W, 185-265 VAC Input Power Supply ...................................................................................... 23

Processor Controlled Supply Turn On/Off............................................................................................................... 24

Key Application Considerations .............................................................................................................................. 26

TOPSwitch-II vs. TOPSwitch-GX ........................................................................................................................ 26

TOPSwitch-FX vs. TOPSwitch-GX...................................................................................................................... 28

TOPSwitch-GXDesign Considerations .............................................................................................................. 28

TOPSwitch-GX Layout Considerations............................................................................................................... 30

Quick Design Checklist........................................................................................................................................ 32

Design Tools......................................................................................................................................................... 32

Product Specifications and Test Conditions .......................................................................................................... 33

Typical Performance Characteristics .................................................................................................................... 40

Part Ordering Information ....................................................................................................................................... 46

Package Outlines ..................................................................................................................................................... 47