TOP232-234
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 DCMAX 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 VOR ......................................................................................... 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
B
7/01
2
ETC [ ETC ]
