Diodes Incorporated
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AP39303 (Not Recommended for new design)

NRND = Not Recommended for New Design

Quasi-Resonant PWM Switcher

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The AP39303 is a highly integrated power switcher with a built-in Quasi-Resonant (QR) PWM controller and a 700V high performance power MOSFET. AP39303 is specially designed for offline power supply that requires ultra-low standby power, high-power density and comprehensive protection. Coordinating with secondary side USBPD or quick charger controller to provide a Flyback charger solution.

At no load or light load, the IC will enter the burst mode to minimize standby power consumption. The minimum switching frequency (typical: 24kHz) is set to avoid the audible noise. When the load increases, the IC will enter QR mode with frequency foldback to improve system efficiency and EMI performance. The maximum switching frequency (typical: 120kHz) is set to clamp the QR
frequency to reduce switching power loss. Furthermore, the frequency dithering function is built in to reduce EMI emission.

The AP39303 provides an inner high-voltage start-up function through HV pin which can reduce the standby loss. Moreover, The AP39303 integrates a VCC LDO circuitry, allowing the LDO to regulate the wide range VCC_IN to an acceptable value. This makes the AP39303 to be a good choice in wide range output voltage application.

Internal piecewise linear line compensation ensures constant output power limit over entire universal line voltage range.

Comprehensive protection features are included, such as brown out protection, cycle-by-cycle current limit, VCC Over Voltage Protection (VOVP), Secondary-side Output OVP (SOVP) and UVP (SUVP), internal OTP, Over Load Protection (OLP) and pins’ fault protection.

Combined with Diodes Incorporated’s synchronous controller APR347, AP39303 system can achieve the higher power conversion efficiency and the better thermal performance.


  • Quasi-Resonant Operation under all Line and Load Condition 
  • Peak Current Mode Control @ DCM
  • High-Voltage Startup
  • Built-In 700V High Performance Power MOSFET
  • Embedded VCC LDO to Guarantee Wide Range VCC_IN Voltage
  • Low VCC Charge Current Reduces Standby Power in Output Short Situation
  • Adaptive Burst Mode Operation with Output Voltage
  • Adaptive Output Power Limit with Output Voltage
  • Non-Audible-Noise Quasi-Resonant Control
  • Soft Start during Startup Process
  • Frequency Fold Back for High Average Efficiency
  • Secondary Winding Short Protection with FOCP
  • Frequency Dithering for Reducing EMI
  • VCC Maintain Mode
  • Useful Pin Fault Protection: 

SENSE Pin Floating 

FB/Opto-Coupler Open/Short

  • Comprehensive System Protection Feature: 

Programmable External OTP

Over Load Protection (OLP)

Brown In/Out Protection

Secondary Side OVP (SOVP) and UVP (SUVP)

  • HSOP-16 (Type SM) Package


  • Switching AC-DC Adapter/Charger
  • ATX/BTX Auxiliary Power
  • Set-Top Box (STB) Power Supply
  • Open Frame Switching Power Supply

Product Specifications

Product Parameters

BNO Auto-Recover
CTRL Pin High Auto-Recover
CTRL Pin Low Auto-Recover
Gate OutputCurrent (mA) 350
HV Start-UpCircuit Yes
LOVP Auto-Recover
Maximum OscillationFrequency (kHz) 65
StartupCurrent (µA) 1
UVLOThresholdon/off (V) 15.8/6.7
VOVP Auto-Recover

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Quality Documentation

Product Change Notices (PCNs)

A PCN may only apply to specific orderable part numbers in this datasheet. Please refer to the corresponding PCN to see the exact orderable part number(s) affected.

PCN # Issue Date Implementation Date Subject
PCN-2594 2022-08-31 2023-02-28 Device End of Life (EOL)