TOP232-234

2

B

7/01

Section List

Pin Functional Description ......................................................................................................................................... 3

TOPSwitch-FX Family Functional Description ......................................................................................................... 4

CONTROL (C) Pin Operation ................................................................................................................................. 4

Oscillator and Switching Frequency ....................................................................................................................... 5

Pulse Width Modulator and Maximum Duty Cycle ................................................................................................. 5

Minimum Duty Cycle and Cycle Skipping ............................................................................................................... 6

Error Amplifier ......................................................................................................................................................... 6

On-chip Current Limit with External Programability ................................................................................................ 6

Line Under-Voltage Detection (UV) ........................................................................................................................ 6

Line Overvoltage Shutdown (OV) ........................................................................................................................... 7

Line Feed Forward with DC

Remote ON/OFF and Synchronization ................................................................................................................... 7

Soft-Start ................................................................................................................................................................ 8

Shutdown/Auto-Restart .......................................................................................................................................... 8

Hysteretic Over-Temperature Protection ................................................................................................................ 8

Bandgap Reference ................................................................................................................................................ 8

High-Voltage Bias Current Source .......................................................................................................................... 8

Using FREQUENCY and MULTI-FUNCTION Pins ..................................................................................................... 9

FREQUENCY (F) Pin Operation ............................................................................................................................. 9

MULTI-FUNCTION (M) Pin Operation .................................................................................................................... 9

Typical Uses of FREQUENCY (F) Pin ...................................................................................................................... 11

Typical Uses of MULTI-FUNCTION (M) Pin ............................................................................................................. 12

Application Examples ............................................................................................................................................... 14

A High Efficiency, 30 W, Universal Input Power Supply ........................................................................................ 14

35 W Multiple Output Power Supply ..................................................................................................................... 15

17 W PC Standby Power Supply .......................................................................................................................... 16

Processor Controlled Supply Turn On/Off ............................................................................................................ 17

Key Application Considerations .............................................................................................................................. 19

TOPSwitch-FX vs. TOPSwitch-ll ........................................................................................................................... 19

TOPSwitch-FX Design Considerations ................................................................................................................. 20

TOPSwitch-FX Selection ................................................................................................................................ 20

Input Capacitor ............................................................................................................................................... 20

Primary Clamp and Output Reflected Voltage V

Output Diode .................................................................................................................................................. 21

Soft-Start ........................................................................................................................................................ 21

EMI ................................................................................................................................................................. 21

Transformer Design ........................................................................................................................................ 21

Standby Consumption .................................................................................................................................... 23

TOPSwitch-FX Layout Considerations ................................................................................................................. 23

Primary Side Connections .............................................................................................................................. 23

Y-Capacitor..................................................................................................................................................... 23

Heat Sinking ................................................................................................................................................... 23

Quick Design Checklist ......................................................................................................................................... 23

Design Tools ......................................................................................................................................................... 23

Product Specifications and Test Conditions .......................................................................................................... 24

Typical Performance Characteristics ...................................................................................................................... 30

Package Outlines ...................................................................................................................................................... 34