General Description
The AP3720 is a low startup current, current mode PWM controller with green-mode operation. The PWM switching frequency at normal operation is 65k, but when the output power drops below the specifically level, the device enters the frequency-drop mode and the typical operating frequency is 20kHz (no audible noise). Additionally, when the load drops to a very low level or zero, the IC operates in so called ‘burst mode’ to minimize switching loss.
   
Features
• Low Startup Current （ 2.5µA ） and Low
    Operating Current (1.2mA)
• Off-line Converter Applied in Sub 25W Range
• Skip Cycle Mode Achieves Low Standby Power
    (<200mW)
• Cycle-by-Cycle Power Limited
• Frequency-drop Mode
• Soft Start with 2ms
• Programmable Drive Current for BJT
• Leading Edge Blanking
• Pre-shutdown Decreases Turn-off Losses
• Reliable Protection:
    Accurate OCP with Line Compensation
    Short Circuit Protection
    Over Voltage Protection for VCC
    Hysteretic Thermal Shutdown Protection
   
Applications
• STB
• Cable Modem
• ADSL Modem
• DVD Recorder