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Primary Side Regulated POWER SWITCHER

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The AP3987CT is a high performance AC/DC power switcher for battery charger and adapter applications with a built-in high performance controller and a built-in 650V high performance MOSFET. It can meet less than 10mW standby power for “Super Star” charger criteria. The device uses Pulse Frequency Modulation (PFM) method to build Discontinuous Conduction Mode (DCM) Flyback power supplies.

The AP3987CT provides accurate Constant Voltage (CV), Constant Current (CC) and outstanding dynamic performance without requiring an opto-coupler. It also eliminates the need of loop compensation circuitry while maintaining stability.

The AP3987CT is equipped with built-in 0.35V output cable drop compensation.

The AP3987CT has internal over temperature protection, and also provides dedicated pin for external over temperature protection.

When the AP3987CT is used with AP4341 or APR3415CT series synchronous rectifier solution, better under-shoot performance and higher conversion efficiency can be achieved.

The AP3987CT provides operating frequency dithering function to improve system EMC performance.

The AP3987CT is packaged in SO-7.


  • Primary-Side Control for Eliminating Opto-Coupler
  • 10mW No-Load Input Power
  • Built-In 650V High Performance MOSFET 
  • Flyback Topology in DCM Operation
  • Built-In 0.35V Cable Compensation for CV
  • Multiple PWM/PFM Control Mode to Improve Audio Noise and Efficiency
  • VCS Jitter to Reduce System EMI
  • Valley-On for the Higher Efficiency and Better EMI
  • Multiple Protections:
    • Over Voltage Protection (OVP)
    • Output Short Circuit Protection (SCP)
    • Transformer Saturation Protection (TSP) via Primary Peak Current Limitation
    • Internal and External Over Temperature Protection (OTP)
  • Matching AP4341 with Schottky or APR3415CT Series Synchronous Rectifier Solution
  • SO-7 Package
  • Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2)
  • Halogen and Antimony Free. “Green” Device (Note 3)


  • Adapter/Chargers for Shaver, Cell/Cordless Phones, PDAs, MP3 and Other Portable Apparatus
  • Standby and Auxiliary Power Supplies

Product Specifications

Product Parameters

BVDSS (Min) (V) 650 V
Collector DC Current (A) 1 A
StartupCurrent (µA) 0.6 µA
OperatingCurrent (µA) 700 µA
UVLOThresholdon/off (V) 13/5.9 V
Power Rating (W) 7.5 W
StandbyPower (Max) (mW) 10 mW
CableCompensation 7%

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Orderable Part Number Buy from Distributor / Contact Sales Request Samples


Authorized Distributor Quantity Inventory Date Countries/Regions Buy Online
Mouser Electronics Inc. 3988 9/30/2022 South America, North America, Asia, Europe, Middle East Buy Now
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