TOP242-249 POWERINT [Power Integrations, Inc.], TOP242-249 Datasheet - Page 29

• Manufacturer Part Number: TOP242-249
• Description: Family Extended Power, Design Flexible,Integrated Off-line Switcher
• Manufacturer: POWERINT [Power Integrations, Inc.]

Table 5 (cont). Comparison Between TOPSwitch-FX and TOPSwitch-GX. *Not available
TOPSwitch-GX Design Considerations
Power Table
Datasheet power table represents the maximum practical
continuous output power based on the following conditions:
TOP242 to TOP246: 12 V output, Schottky output diode,
150 V reflected voltage (VOR) and efficiency estimates from
curves contained in application note AN-29. TOP247 to TOP249:
Higher output voltages used with a maximum output current of
6 A.
For all devices a 100 VDC minimum for 85-265 VAC and 250
VDC minimum for 230 VDC are assumed and sufficient heat
sinking to keep device temperature ≤ 100 °C. Power levels
shown in the power table for the R package device assume
6.45 cm
adapter, or 19.4 cm
TOPSwitch-GX Selection
Selecting the optimum TOPSwitch-GX depends upon required
maximum output power, efficiency, heat sinking constraints
and cost goals. With the option to externally reduce current
limit, a larger TOPSwitch-GX may be used for lower power
Function
P/G Package Current
Limits
Y/R Package Current
Limits
Thermal Shutdown
Maximum Duty Cycle
Reduction Threshold
Line Under-Voltage
Negative (turn-off)
Threshold
Soft-Start
2
of 610 g/m
2
in an open frame.
2
copper heat sink area in an enclosed
TOPSwitch-FX
Identical to Y
packages
100%
(R package N/A*)
125 °C min.
70 °C hysteresis
90 µA
N/A*
10 ms (duty cycle) 10 ms (duty cycle + current
TOP243P or G and
TOP244P or G internal
current limits reduced
90% (for equivalent R
130 °C min. 75 °C
hysteresis
60 µA
40% of positive (turn-on)
threshold
limit)
TOPSwitch-GX
applications where higher efficiency is needed or minimal heat
sinking is available.
Input Capacitor
The input capacitor must be chosen to provide the minimum
DC voltage required for the TOPSwitch-GX converter to maintain
regulation at the lowest specified input voltage and maximum
output power. Since TOPSwitch-GX has a higher DC
TOPSwitch-II, it is possible to use a smaller input capacitor.
For TOPSwitch-GX, a capacitance of 2 µF per watt is possible
for universal input with an appropriately designed transformer.
Primary Clamp and Output Reflected Voltage V
A primary clamp is necessary to limit the peak TOPSwitch-GX
drain to source voltage. A Zener clamp requires few parts and
takes up little board space. For good efficiency, the clamp
Zener should be selected to be at least 1.5 times the output
reflected voltage V
time short. When using a Zener clamp in a universal input
application, a V
for the absolute tolerances and temperature variations of the
Zener. This will ensure efficient operation of the clamp circuit
and will also keep the maximum drain voltage below the rated
breakdown voltage of the TOPSwitch-GX MOSFET.
DS (ON)
)
OR
of less than 135 V is recommended to allow
• Matches device current limit to
• Allows more continuous design to
• Minimizes transformer core size
• Optimizes efficiency for most
• Allows higher output powers in
• Reduces output line frequency
• D
• Provides a well defined turn-off
• Gradually increasing current limit
• Further reduces component
OR
TOPSwitch-GX Advantages
package dissipation capability
lower device dissipation (lower RMS
currents)
high ambient temperature
applications
ripple at low line
forward design
threshold as the line voltage falls
in addition to duty cycle during soft-
start further reduces peak current
and voltage
stresses during start up
as this keeps the leakage spike conduction
applications
MAX
August 8, 2000
reduction optimized for
TOP242-249
7/01
OR
MAX
E
29
than