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 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
2
B
7/01
PAM [ POWER ANALOG MICOELECTRONICS ]
