Diodes Incorporated APR349W6-7

Overview

APR349W6-7 from Diodes Incorporated is a secondary-side synchronous rectification controller IC for flyback SMPS, supporting CCM/DCM/QR operation modes with intelligent on-time control, 3.3–24V output voltage range, and integrated PLR power supply. It drives external MOSFETs in high-side or low-side configurations to replace Schottky diodes in AC/DC adapters and fast-charging systems.

For engineers reviewing the APR349W6-7 datasheet, APR349W6-7 pinout, APR349W6-7 application, or APR349W6-7 equivalent, key selection criteria include gate drive timing (tD_ON ≤ 60 ns, tD_OFF ≤ 45 ns), DRAIN-sense thresholds (VON_TH = −200 mV typ), smart-blanking protection against shoot-through, and SOT26 package compatibility with high-density PCB layouts.

Technical Context

The APR349W6-7 implements dual-path VDD biasing: Pulse Linear Regulator (PLR) activates below ~4.75V VOUT, while LDO takes over above that threshold. Its DRAIN-sense architecture uses volt-second product integration (Kqs = 0.5 mA·μs typ) with Rx resistor programming to distinguish true conduction from resonant ringing.

Gate control employs forward regulation (VON_REG = −40 mV typ) to maintain constant channel voltage during decreasing secondary current, combined with minimum on/off time blanking (tON_MIN = 0.9 μs typ, tOFF_MIN = 0.5 μs typ) and smart-blanking (20 μs disable after two false triggers within 4 μs) to ensure safe switching under transient conditions.

Key Specifications

Pinout & Package

SOT26 (Type CJ) package: 6-pin, surface-mount, lead-free, MSL Level 1, 0.016 g mass, 2.9 mm × 2.8 mm footprint with 0.95 mm pitch.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar secondary-side synchronous rectification controller applications.

Compared with MP6908GJ-Z and SRK1001TR, the APR349W6-7 uniquely combines programmable volt-second detection, dual-mode VDD supply, and smart-blanking - making it optimal for adaptive, wide-output, high-efficiency QR flyback converters where reliability under dynamic load and light-load conditions is critical.

Availability

APR349W6-7 is available at Aetrix Electronics and suitable for adaptive fast chargers, AC/DC wall adapters, and battery-powered SMPS requiring stable component supply, long-term lifecycle support, and RoHS-compliant manufacturing.

Supply support for APR349W6-7 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, specializing in high-efficiency power management, signal integrity, and timing solutions for consumer, industrial, and automotive markets.

The APR349 belongs to Diodes' secondary-side synchronous rectification controller product line, designed specifically to replace Schottky diodes in isolated flyback converters while maintaining robustness across CCM, DCM, and quasi-resonant operation modes.

FAQ

What is the minimum recommended Rx resistor value for stable operation?

The Rx resistor sets the volt-second threshold (Area2 = Rx × Kqs). With Kqs = 0.5 mA·μs typ, Diodes recommends Rx ≥ 10 kΩ to ensure sufficient margin against noise-induced false triggering while maintaining responsiveness. Values below 5 kΩ risk premature turn-on during ringing; values above 100 kΩ may delay conduction under light load.

Can APR349W6-7 be used in high-side configuration with N-channel MOSFETs?

Yes - the APR349W6-7 supports high-side N-MOSFET synchronous rectification. Its DRAIN-sense architecture references GND, not source, so it directly senses drain voltage regardless of MOSFET orientation. The gate driver outputs relative to GND, requiring bootstrap or isolated gate drive only if floating source is used; standard high-side layout with source tied to output rail is fully supported.

How does the smart-blanking function interact with QR mode transitions?

In QR mode, the smart-blanking function activates only during tOFF periods when false DRAIN triggers occur. If two such events happen within 4 µs, the gate driver blanks for 20 µs - preventing shoot-through during valley-switching transitions where primary and secondary MOSFETs could overlap. This preserves zero-voltage switching benefits while adding fault tolerance during boundary conditions like output step changes.

Is external capacitor required on the VDD pin, and what value is recommended?

Yes - a 3.3 µF ceramic capacitor (X5R/X7R, 10 V rating) is required between VDD and GND per Diodes' datasheet. This stabilizes the internal regulator during gate switching transients and prevents UVLO dropout during peak gate current demand (up to 3.5 A sink). Smaller values (<2.2 µF) cause erratic gate behavior; larger values (>10 µF) delay startup but are acceptable if startup time is not critical.