• Integrated 700V E-Mode GaN FET (160mΩ)
• Combined CCM+QR Operating Modes
• Soft GaN Gate Drive for Optimized EMI Performance
• Wide VCC Operating Range: 7-85V
• Switching Frequency Range: 25kHz–500kHz
• Frequency Modulation to Reduce EMI Noise
• Integrated 700V HV Startup Circuitry
• Programmable Output OVP and UVP
• Brown-In/Out Protection
• Current Sense Resistor Short-Circuit Protection
• Winding or SR Short-Circuit Protection
• Internal and External OTP
• Compact Package: SSOP9E 

The SY50355 is a high frequency flyback converter operating in continuous conduction mode (CCM) and quasi-resonant (QR) mode. It integrates an enhancement-mode (E-Mode) GaN FET to enable a compact PCB layout. The device is designed for power delivery (PD) capable adapters and quick chargers. Its maximum operating frequency of up to 500kHz allows for reduced transformer, PCB, and capacitor sizes.

The SY50355 operates using peak current control. At low input voltage and heavy load the device enables CCM mode, allowing for reduced transformer and PCB size. At high input voltage, CCM mode is disabled, and the SY50355 switches to QR mode. In this mode, the GaN FET turns on at the valley point to minimize switching losses. As the load decreases, the SY50355 enters DCM mode to lower the switching frequency and improve efficiency. Under very light load conditions, the device enters burst mode to further reduce power loss.

The SY50355 integrates comprehensive protection features to ensure reliable operation, including high voltage (HV) startup, brown-out protection, output and VCC overvoltage protection (OVP), output undervoltage protection (UVP), internal and external overtemperature protection (OTP), and open-loop protection (OLP).

It is recommended to use the SY5236 or SY5236A as a secondary-side synchronous rectifier (SR) controller in conjunction with the SY50355 to enable zero voltage switching (ZVS) at high input voltage for improved efficiency. The SY50355 is available in a compact SSOP9E package.