AP3781 PRIMARY SIDE REGULATED SWITCHING MODE POWER SUPPLY CONTROLLER Description Pin Assignments The AP3781 is a high performance AC/DC power supply controller for battery charger and adapter applications. The controller regulates the (Top View) output voltage and current in the primary side by Pulse Frequency Modulation in Discontinuous Conduction Mode (DCM). The AP3781 operates in Pulse Frequency Modulation (PFM) mode 1 8 NC GND and peak current Amplitude Modulation (AM) mode to form a fine tune frequency curve within the whole power range. Therefore, AP3781 2 7 can achieve high average efficiency and improve audible noise. FB OUT The AP3781 provides comprehensive protections without additional 3 VCC 6 NC circuitry. It contains V over voltage protection, output over voltage CC protection, output under voltage protection, output short circuit 5 4 OTP CS protection, cycle-by-cycle current limit, open loop protection, external OTP and internal OTP, etc. The AP3781 is packaged in SO-8. SO-8 Features Applications Primary Side Control for Eliminating Opto-Coupler Routers 75mW No-Load Input Power Power Tools Flyback Topology in DCM Operation Set-Top Box (STB) Power Supply External Adjustable Over Temperature Protection Smart Speakers Fixed Internal Cable Compensation: 3% Network Adaptors External Cable Compensation: 3% to 8% Multiple Segment AM/PFM Control Mode to Improve Audio Noise and Efficiency Ultra Low Under Voltage Protection, Support Wide Operating Voltage for Power Tool Motor Drive Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2) Halogen and Antimony Free. Green Device (Note 3) For automotive applications requiring specific change control (i.e. parts qualified to AEC-Q100/101/200, PPAP capable, and manufactured in IATF 16949 certified facilities), please contact us or your local Diodes representative. AP3781 Typical Applications Circuit C5 R11 FR1 DB1 T1 L1 C3 R4 Np R1 D3 + + Ns R12 + + C6 C7 D1 R3 R2 C1 C2 12V/2A D2 R5 + Na C4 AP3781 U1 CY1 GND VCC R6 Q1 R8 OUT OTP CS FB R7 NTC R9 R10 Pin Descriptions Pin Number Pin Name Function 1 GND The ground of the controller 2 FB The CV regulation is realized based on the voltage sampling of this pin 3 VCC The VCC pin supplies the power for the IC The CS is the current sense pin of the IC. The IC will turn off the power MOSFET 4 CS according to the voltage on the CS pin 5 OTP Adjustable over temperature protection by external NTC resistor 6 NC No Connection 7 OUT Output pin to drive external MOSFET 8 NC No Connection 2 of 15 May 2020 AP3781 www.diodes.com Diodes Incorporated Document number: DS42518 Rev. 2 - 2