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Technical content
©SiFirst Technology - 1 - Confidential SiFirst_DS_1546_V1.0 SF1546
FEATURES
◆ Built-in 650V Power MOSFET ◆ Proprietary η-BalanceTM Control to Boost Light Load Efficiency ◆ Proprietary “Zero OCP /OPP Recovery Gap ” Control ◆ Fixed 65KHz Switching Frequency ◆ Built-in Soft Start Function ◆ Very Low Startup Current ◆ Frequency Reduction and Burst Mode Control for Energy Saving ◆ Current Mode Control ◆ Built-in Frequency Shuffling ◆ Built-in Synchronous Slope Compensation ◆ Cycle-by-Cycle Current Limiting ◆ Built-in Leading Edge Blanking (LEB) ◆ Constant Power Limiting ◆ Pins Floating Protection ◆ Audio Noise Free Operation ◆ VDD OVP & Clamp ◆ VDD Under Voltage Lockout (UVLO)
APPLICATIONS
Offline AC/DC Flyback Converter for ◆ AC/DC Adaptors ◆ Open-frame SMPS ◆ Set-Top Box Power Supplies ◆ ATX Standby Power GENERAL DESCRIPTION SF1546 is a high performance, high efficiency , highly integrated current mode PWM power switch for offline flyback converter applications. In SF1546, PWM switching frequency with shuffling is fixed to 65KHz and is trimmed to tight range . When the output power demands decrease, the IC decreases switching frequency based on the proprietaryη-BalanceTM 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 provides excellent efficiency without audio noise. The IC can achieve “Zero OCP/OPP Recovery Gap ” using SiFirst ’s proprietary control algorithm. Meanwhile, the OCP/OPP variation versus universal line input is compensated. The IC has built-in synchronized slope compensation to prevent sub-harmonic oscillation at high PWM duty output. The IC also has b uilt-in soft start function to soften the stress on the MOSFET during power on period. SF1546 integrates functions and protections of Under Voltage Lockout (UVLO), VCC Over Voltage Protection (OVP), Cycle- by-cycle Current Limiting (OCP), Pins Floating Protection, Over Load Protection (OLP), VCC Clamping, Leading Edge Blanking (LEB), etc. SF1546 is available in DIP8 packages. TYPICAL APPLICATION EMI FilterAC IN SF1546 DC Out TL431 VDD FB CS GND NC Drain Drain Drain η-BalanceTM PWM Power Switch Fixed 65KHz Fsw Sifirst confidential
©SiFirst Technology - 2 - Confidential SiFirst_DS_1546_V1.0 SF1546 Pin Configuration NC VDD FB GND Drain DIP8 CS Drain Drain
Ordering Information
Part Number Top Mark Package Tape & Reel SF1546DP SF1546DP DIP8 RoHs Output Power Table(1) Part Number 230VAC ± 15%(2) 85-265VAC Adapter(3) Open Frame(4) Adapter(3) Open Frame(4) SF1546DP 12W 15W 10W 13W Note 1. The Max. output power is limited by junction temperature Note 2. 230VAC or 100/115VAC with doublers Note 3. Typical continuous power in a non- ventilated enclosed adapter with sufficient drain pattern as a heat sink at 50 oC ambient. Note 4. Max. practical continuous power in a open- frame design with sufficient drain pattern as a heat sink at 50 oC ambient. Marking Information S F 1 5 4 6 D P Y WW YWW: Year&Week code Sifirst confidential