SF1533SG PDF Datasheet – PWM Power Switch

Part Number: SF1533SG

Function: PWM Power Switch

Package: SOP 8 Pin Type

Manufacturer: SiFirst Technology

Images:SF1533SG pdf


SF1533SG is a high performance, high efficiency, highly integrated current mode PWM power switch for offline flyback converter applications. In SF1533SG, 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. SF1533SG 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. SF1533SG is available in SOP8 packages.


SF1533SG pinout datasheet


1. Built-in 600V Power MOSFET

2. Proprietary η -BalanceTM Control to Boost Light Load Efficiency

3. Proprietary “Zero OCP/OPP Recovery Gap” Control

4. Fixed 50KHz Switching Frequency

5. Built-in Soft Start Function

6. Very Low Startup Current

7. Frequency Reduction and Burst Mode Control for Energy Saving

8. Current Mode Control

9. Built-in Frequency Shuffling

10. Built-in Synchronous Slope Compensation

11. Cycle-by-Cycle Current Limiting

12. Built-in Leading Edge Blanking (LEB)


1. AC/DC Adaptors

2. Open-frame SMPS

3. Set-Top Box Power Supplies

4. ATX Standby Power


SF1533SG PDF Datasheet