SF1533 PDF – PWM Power Switch – SiFirst

Part Number: SF1533

Function: PWM Power Switch

Package: SOP 8 Pin Type

Manufacturer: SiFirst Technology


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SF1533 image

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SF1533 is a high performance, high efficiency, highly integrated current mode PWM power switch for offline flyback converter applications. In SF1533, PWM switching frequency with shuffling is fixed to 50KHz and is trimmed to tight range. When the output power demands decrease, the IC decreases switching frequency based on the proprietary η -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 built-in soft start function to soften the stress on the MOSFET during power on period. SF1533 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. SF1533 is available in SOP8 packages. TYPICAL APPLICATION AC IN EMI Filter DC Out SF1533 1 NC GND 8 2 VDD GND 7 3 FB 4 CS Drain 6 Drain 5 ©SiFirst Technology -1- TL431 Confidential SiFirst_DS_1533_V1.1 Pin Configuration NC VDD FB CS 18 SOP8 27 36 45 GND GND Drain Drain SF1533 Ordering Information Part Number Top Mark SF1533SG SF1533SG SF1533SGT SF1533SG SOP8 SOP8 Package Green Green Tape & Reel Yes Output Power Table(1) Part Number SF1533 230VAC ± 15%(2) Adapter(3) 7W 85-265VAC Adapter(3) 5.5W 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 YWW: Year&Week



◆ Built-in 600V Power MOSFET ◆ Proprietary η-BalanceTM Control to Boost Light Load Efficiency ◆ Proprietary “Zero OCP/OPP Recovery Gap” Control ◆ Fixed 50KHz 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  […]


SF1533 Datasheet