Datasheet

TOP242-250
27
I
4/03
Key Application Considerations
TOPSwitch-II vs. TOPSwitch-GX
Table 4 compares the features and performance differences
between TOPSwitch-GX and TOPSwitch-II. Many of the new
features eliminate the need for additional discrete components.
Other features increase the robustness of design allowing cost
savings in the transformer and other power components.
Function TOPSwitch-II TOPSwitch-GX Figures TOPSwitch-GX Advantages
Soft-Start N/A* 10 ms • Limits peak current and voltage
component stresses during start-up
• Eliminates external components
used for soft-start in most
applications
• Reduces or eliminates output
overshoot
External Current Limit N/A* Programmable 11,20,21, • Smaller transformer
100% to 30% of 24,25,27, • Higher efficiency
default current 28,34,35, • Allows power limiting (constant over-
limit 38,39 load power independent of line
voltage
• Allows use of larger device for lower
losses, higher efficiency and smaller
heatsink
DC
MAX
67% 78% 7 • Smaller input cap (wider dynamic
range)
• Higher power capability (when used
with RCD clamp for large V
OR
)
• Allows use of Schottky secondary
rectifier diode for up to 15 V output
for high efficiency
Line Feed Forward with N/A* 78% to 38% 7,11,17, • Rejects line ripple
DC
MAX
Reduction 26,27,28,
31,40
Line OV Shutdown N/A* Single resistor 11,17,19, • Increases voltage withstand cap-
programmable 26,27,28, ability against line surge
31,33,40
Line UV Detection N/A* Single resistor 11,17,18, • Prevents auto-restart glitches
programmable 26,27,28, during power down
31,32,40
Switching Frequency 100 kHz ±10% 132 kHz ±6% 13,15 • Smaller transformer
• Below start of conducted EMI limits
Switching Frequency N/A* 66 kHz ±7% 14,15 • Lower losses when using RC and
Option (Y, R and F RCD snubber for noise reduction in
Packages) video applications
• Allows for higher efficiency in
standby mode
• Lower EMI (second harmonic below
150 kHz)
Frequency Jitter N/A* ±4 kHz@132 kHz 9,46 • Reduces conducted EMI
±2 kHz@66 kHz
Frequency Reduction N/A* At a Duty Cycle 7 • Zero load regulation without dummy
below 10% load
• Low power consumption at no load
Table 4. Comparison Between TOPSwitch-II and TOPSwitch-GX. (continued on next page) *Not available