Rev. D 10/20

2

TOP232-234

www.power.com

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 Undervoltage Detection (UV)............................................................................................................................. 6

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

Line Feed-Forward with DC

MAX Reduction ................................................................................................................ 7

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

OR

.......................................................................................... 20

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