TOP252-262
Key Application Considerations
TOPSwitch-HX vs. TOPSwitch-GX
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.
Table 4 compares the features and performance differences
between TOPSwitch-HX and TOPSwitch-GX. Many of the new
TOPSwitch-HX vs. TOPSwitch-GX
Function
TOPSwitch-GX
TOPSwitch-HX
TOPSwitch-HX Advantages
EcoSmart
Linear frequency reduction to Multi-mode operation with
•
Improved efficiency over load (e.g. at 25% load
point)
Improved standby efficiency
Improved no-load consumption
30 kHz (@ 132 kHz) for
duty cycles < 10%
linear frequency reduction to
30 kHz (@ 132 kHz) and
multi-cycle modulation
•
•
(virtually no audible noise)
Output Overvoltage
Protection (OVP)
Not available
User programmable primary
or secondary hysteretic or
latching OVP
•
•
Protects power supply output during open loop fault
Maximum design flexibility
Line Feed-Forward with Duty Linear reduction
Cycle Reduction
Dual slope reduction with
lower, more accurate onset
point
•
•
Improved line ripple rejection
Smaller DC bus capacitor
Switching Frequency DIP-8
Package
132 kHz
66 kHz
•
•
Increased output power for given MOSFET size due
to higher efficiency
Lowest MOSFET On
Resistance in DIP-8 Package
3.0 Ω (TOP246P)
1.8 Ω (TOP258P)
Increased output power in designs without external
heatsink
I2f Trimming
Not available
5.6%
-10% / +20%
2%
•
•
Increased output power for given core size
Reduced over-load power
Auto-restart Duty Cycle
•
Reduced delivered average output power during
open loop faults
Frequency Jitter
4 kHz @ 132 kHz
2 kHz @ 66 kHz
5 kHz @ 132 kHz
2.5 kHz @ 66 kHz
•
Reduced EMI filter cost
Increased design margin
Thermal Shutdown
130 °C to 150 °C
30%-100% of ILIMIT
135 °C to 150 °C
•
•
External Current Limit
30%-100% of ILIMIT, additional
trim at 0.7 × ILIMIT
Reduced tolerances when current limit is set
externally
Line UV Detection Threshold 50 μA (2 MΩ sense
25 μA (4 MΩ sense
impedance)
•
Reduced dissipation for lower no-load consumption
impedance)
Soft-Start
10 ms duty cycle and current 17 ms sweep through multi-
•
•
Reduced peak current and voltage component
stress at startup
Smooth output voltage rise
limit ramp
mode characteristic
Table 4.
Comparison Between TOPSwitch-GX and TOPSwitch-HX.
25
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Rev. F 01/09
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