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
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
.........................................................................................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