AP3720 (Not Recommended for new design)

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 cal°C ‘burst mode’ to minimize switching loss. The IC integrated a lot of functions such as the Lead-Edge Blanking (LEB) of the current sensing, internal slope compensation, line compensation, and several protection features. The protection functions include cycle-by-cycle current limit (OCP), VCC over voltage protection (OVP), OTP and OLP.

Feature(s)

• 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

Application(s)

• STB
• Cable Modem
• ADSL Modem
• DVD Recorder