Diodes Incorporated AP3968DMTR-G1

Overview

AP3968DMTR-G1 from BCD Semiconductor is a primary-side regulation (PSR) power switcher IC integrating a 700V NPN transistor, designed for off-line flyback SMPS up to 4W output. It delivers opto-coupler–free constant voltage (CV) and constant current (CC) regulation with ±5% output accuracy, internal cable compensation (0.35V typical), and random frequency modulation for EMI reduction. Used in 5V/700mA adapters for ADSL, set-top boxes, and auxiliary supplies.

For engineers reviewing the AP3968DMTR-G1 datasheet, AP3968DMTR-G1 pinout, AP3968DMTR-G1 application, or AP3968DMTR-G1 equivalent, this page details its PFM control architecture, SOIC-7 integrated switch topology, thermal shutdown behavior (160°C), and CV/CC loop interaction - critical for low-component-count AC/DC design validation.

Technical Context

The AP3968DMTR-G1 implements primary-side regulation via auxiliary winding feedback at the FB pin (4.278V typical threshold), eliminating secondary-side sensing circuitry. Its built-in NPN transistor (VCBO = 700V, hFE = 15–23) enables direct primary switching without external drivers.

It operates in pulse frequency modulation (PFM) mode with variable switching frequency up to 60 kHz, uses leading-edge blanking (500 ns) on the CS pin to reject turn-on spikes, and applies fixed-ratio timing (T_on/T_off = 3/4) in CC mode to maintain load-current stability across line and load variations.

Key Specifications

Pinout & Package

AP3968DMTR-G1 is housed in a standard SOIC-7 package (5.10 mm × 4.00 mm × 1.75 mm, 1.27 mm pitch), with exposed pad not electrically connected. The package supports surface-mount reflow assembly and provides adequate thermal dissipation (θ_JA = 80°C/W) for 4W operation without heatsink.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar primary-side regulation switcher applications.

Compared with MP157DS-LF-Z and LNK304DG, AP3968DMTR-G1 uniquely combines 700V BJT integration, factory-trimmed cable compensation, and SOIC-7 footprint - making it optimal for 4W, opto-free, low-BOM adapter designs where thermal margin and load-step regulation are prioritized over maximum switching frequency.

Availability

AP3968DMTR-G1 is available at Aetrix Electronics and suitable for ADSL adapters, set-top box auxiliary supplies, and DVD player power supplies requiring stable component supply, RoHS-compliant green packaging, and tape-and-reel delivery for SMT production.

Supply support for AP3968DMTR-G1 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

BCD Semiconductor Manufacturing Limited is a Shanghai-based analog and power IC designer specializing in high-voltage process technologies for AC/DC, DC/DC, and motor control applications.

The AP3968D belongs to BCD's PSR Switcher product line, engineered specifically for cost-sensitive, low-power offline SMPS where integration, reliability, and regulatory compliance (RoHS/Green) are essential design constraints.

FAQ

What is the maximum continuous output power supported by AP3968DMTR-G1?

The AP3968DMTR-G1 is rated for up to 4W continuous output power in flyback topology, validated in the 5V/700mA reference design (Figure 11). This limit arises from thermal constraints of the integrated 700V NPN transistor and SOIC-7 package (θ_JA = 80°C/W), not electrical capability alone. Exceeding 4W risks thermal shutdown or reduced lifetime under sustained load.

How does the internal cable compensation function work, and what external component is required?

The AP3968DMTR-G1 applies a fixed 0.35V offset to the FB regulation loop to counteract voltage drop across output cables under load. A 0.01μF ceramic capacitor must be placed between the CPC pin and GND to filter noise and stabilize the compensation reference. No resistor network or external op-amp is needed - the function is fully integrated and factory-trimmed.

Can AP3968DMTR-G1 operate without an auxiliary winding?

No. The AP3968DMTR-G1 requires an auxiliary winding on the transformer to provide both VCC bias (via pin 3) and output voltage feedback (via pin 2/FB). The FB pin senses rectified auxiliary voltage proportional to the output, enabling primary-side regulation. Omitting the auxiliary winding disables startup, regulation, and all protection functions.

What is the purpose of the dual collector pins (pins 5 and 6) in SOIC-7 package?

Pins 5 and 6 are internally bonded to the same collector node of the integrated NPN transistor, providing parallel current paths and improved thermal conduction to the PCB copper. This dual-pin configuration reduces effective lead resistance and enhances power handling - critical for sustaining 0.8A DC collector current in a small SOIC-7 footprint without excessive self-heating.