TOPSwitch™-FX uses the proven TOPSwitch topology and cost effectively integrates many new functions that reduce system cost and, at the same time, improve design flexibility, performance and energy efficiency. Like TOPSwitch, the high-voltage power MOSFET, PWM control, fault protection and other control circuitry are all integrated onto a single CMOS chip, but with two added terminals. The first one is a MULTI-FUNCTION (M) pin, which implements programmable line OV/UV shutdown and line feed forward/DCMAX reduction with line voltage. The same pin can be used instead to externally set an accurate current limit. In either case, this pin can also be used for remote ON/OFF or to synchronize the oscillator to an external, lower frequency signal. The second added terminal is the FREQUENCY (F) pin and is available only in the Y package. This pin provides the half frequency option when connected to CONTROL (C) instead of SOURCE (S). The features on the new pins can be disabled by shorting them to the SOURCE, which allows the device to operate in a three terminal TOPSwitch mode, but with the following new transparent features: soft-start, cycle skipping, 132 kHz switching frequency, frequency jittering, wider DCMAX.
Product Highlights
Lower System Cost, High Design Flexibility
• Features eliminate or reduce cost of external components
• Fully integrated soft-start for minimum stress/overshoot
• Externally settable accurate current limit
• Wider duty cycle for more power, smaller input capacitor
• Line under-voltage (UV) detection: no turn off glitches
• Line overvoltage (OV) shutdown extends line surge limit
• Line feed-forward with maximum duty cycle (DCMAX) reduction rejects ripple and limits DCMAX at high line
• Single resistor sets OV/UV thresholds, DCMAX reduction
• Frequency jittering reduces EMI and EMI filtering costs
• Regulates to zero load without dummy loading
• 132 kHz frequency reduces transformer/power supply size
• Half frequency option for video applications
• Hysteretic thermal shutdown for automatic recovery
• Large thermal hysteresis prevents PC board overheating
• Standard packages with omitted pins for large creepage
• Active-on and active-off remote ON/OFF capability
• Synchronizable to a lower frequency EcoSmart™– Energy Efficient
• Cycle skipping reduces no-load consumption
• Reduced consumption in remote off mode
• Half frequency option for high efficiency standby
• Allows shutdown/wake-up via LAN/input port
(Picture: Pinout)
