TOP242-249
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*
67%
Programmable
100% to 30% of 24,25,27, • Higher efficiency
default current
limit
11,20,21, • Smaller transformer
28,34,35, • Allows power limiting (constant over-
38,39
load power independent of line
voltage
• Allows use of larger device for lower
losses, higher efficiency and smaller
heatsink
DCMAX
78%
7
• Smaller input cap (wider dynamic
range)
• Higher power capability (when used
with RCD clamp for large VOR)
• Allows use of Schottky secondary
rectifier diode for up to 15 V output
for high efficiency
Line Feed Forward with N/A*
DCMAX Reduction
78% to 38%
7,11,17,
26,27,28,
31,40
• Rejects line ripple
Line OV Shutdown
Line UV Detection
Switching Frequency
N/A*
N/A*
Single resistor
programmable
11,17,19, • Increases voltage withstand cap-
26,27,28,
31,33,40
ability against line surge
Single resistor
programmable
11,17,18, • Prevents auto-restart glitches
26,27,28,
during power down
31,32,40
100 kHz 10%
N/A*
132 kHz 6%
66 kHz 7%
13,15
14,15
• Smaller transformer
• Below start of conducted EMI limits
Switching Frequency
Option (Y and R
Packages)
• Lower losses when using RC and
RCD snubber for noise reduction in
video applications
• Allows for higher efficiency in
standby mode
• Lower EMI (second harmonic below
150 kHz)
Frequency Jitter
N/A*
N/A*
4 kHz@132 kHz 9,46
2 kHz@66 kHz
• Reduces conducted EMI
Frequency Reduction
At a Duty Cycle
below 10%
7
• Zero load regulation without dummy
load
• Low power consumption at no load
Table 4. Comparison Between TOPSwitch-II and TOPSwitch-GX. (continued on next page) *Not available
E
7/01
August 8, 2000
27
POWERINT [ Power Integrations ]
