η-Balance^TM Current Mode PWM Switch^@65KHz

EATURES

◆   Less than 75mW Standby Power

◆   Built-in 650V Power MOSFET

◆   Proprietary η-Balance^TM Control to Boost Light Load Efficiency

◆   Proprietary “Zero OCP/OPP Recovery Gap” Control

◆   Proprietary “Audio Noise Free OCP Compensation”

◆   Dmax up to 80%

◆   Fixed 65KHz Switching Frequency

◆   Built-in Frequency Shuffling

◆   Built-in Soft Start Function

◆   Frequency Reduction and Burst Mode Control for Energy Saving

◆   Built-in Synchronous Slope Compensation

◆   Cycle-by-Cycle Current Limiting

◆   Built-in Leading Edge Blanking (LEB)

◆   Current Mode Control

◆   Pin Floating Protection

◆   Very Low Startup Current

◆   Audio Noise Free Operation

◆   VDD UVLO & OVP

APPLICATIONS

Offline AC/DC Flyback Converter for

◆   AC/DC Adaptors

◆   Open-frame SMPS

◆   Laptop Charger

GENERAL DESCRIPTION

SF6649 is a high performance, high efficiency, highly integrated current mode PWM controller for offline flyback converter applications.

In SF6649, PWM switching frequency with shuffling is fixed 65KHz and is trimmed to tight range. When the output power demands decrease, the IC decreases switching frequency based on the proprietaryη-Balance^TM control to boost power conversion efficiency at the light load. When output power falls below a given value, the IC enters into burst mode and can achieve less than 75mW no load power.

The IC can achieve “Zero OCP/OPP Recovery Gap” using SiFirst’s proprietary control algorithm. SF6649 also has built in proprietary “Audio Noise Free OCP Compensation”, which can achieve constant power limiting and can achieve audio noise operation at heavy loading when line input is around 90VAC.

SF6649 integrates functions and protections of Under Voltage Lockout (UVLO), VDD Over Voltage Protection (OVP), Cycle-by-cycle Current Limiting (OCP), Pins Floating Protection, Over Load Protection (OLP), Gate Clamping, Leading Edge Blanking (LEB), Soft Start, etc.

SF6649 is available in SOP8 package.

TYPICAL APPLICATION