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