Diodes Incorporated BZX84C3V9-7-F

Overview

BZX84C3V9-7-F from Diodes Incorporated is a 3.9 V, 350 mW surface-mount Zener diode in SOT23 package, designed for precision voltage regulation and reference applications at 5 mA test current, with ±0.2 V tolerance (3.7–4.1 V), 90 Ω dynamic impedance, and −3.5 mV/°C temperature coefficient. It serves as a stable shunt voltage reference in low-power power supply feedback loops and sensor biasing circuits.

For engineers reviewing the BZX84C3V9-7-F datasheet, BZX84C3V9-7-F pinout, BZX84C3V9-7-F application, or BZX84C3V9-7-F equivalent, key selection criteria include Zener voltage accuracy, thermal coefficient, power derating behavior, reverse leakage at VR = 1.0 V, and SOT23 footprint compatibility with automated assembly.

Technical Context

This Zener diode operates in reverse breakdown mode to maintain a stable reference voltage across its terminals under varying load and temperature conditions. Its planar die construction ensures consistent breakdown characteristics and low noise performance, while the SOT23 package supports high-density PCB layouts and reflow-compatible manufacturing.

The device exhibits a nominal Zener voltage of 3.9 V at 5 mA (IZT), with maximum dynamic impedance of 90 Ω at IZT and 600 Ω at knee current (IZK = 1.0 mA). Its negative temperature coefficient (−3.5 mV/°C) enables predictable drift compensation in multi-device reference networks.

Key Specifications

Pinout & Package

Package: SOT23 - molded plastic case, UL 94V-0 rated, matte tin-plated alloy 42 leadframe, polarity indicated by cathode band on top view.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar Zener reference applications.

Compared with MMBZ5227BS-7-F and BZX84-C3V9,115, the BZX84C3V9-7-F offers superior low-current regulation (5 mA IZT), tighter voltage tolerance, and higher power margin-critical for precision analog and automotive-compliant designs where thermal stability and long-term drift matter.

Availability

BZX84C3V9-7-F is available at Aetrix Electronics and suitable for power supply feedback references, sensor bias networks, overvoltage protection circuits, and ADC input limiting requiring stable component supply and AEC-Q101 reliability assurance.

Supply support for BZX84C3V9-7-F 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, headquartered in Plano, Texas, with design, manufacturing, and sales operations across Asia, Europe, and North America.

The BZX84 series belongs to Diodes' standard Zener diode product line, engineered for high-volume, cost-sensitive applications demanding AEC-Q101 qualification, green compliance, and robust SMT manufacturability in consumer, industrial, and automotive systems.

FAQ

What is the maximum continuous Zener current for BZX84C3V9-7-F at 70°C ambient?

At 70°C ambient, the device's power dissipation must be derated per Fig. 1 in DS18001 Rev. 33-2. With 350 mW rated at 25°C and linear derating at 2.8 mW/°C above 25°C, maximum allowable power at 70°C is 224 mW. At 3.9 V, this corresponds to ~57.4 mA continuous Zener current-though practical operation should remain below 20 mA to avoid thermal runaway and maintain voltage stability.

Does BZX84C3V9-7-F have a specified capacitance value?

No specific capacitance value is listed in the DS18001 datasheet for BZX84C3V9-7-F. However, Fig. 5 shows typical total capacitance for 3.9 V Zeners is ~50 pF at VR = 0 V and decreases with increasing reverse voltage; at VR = 1 V, capacitance is approximately 35–40 pF. This parasitic capacitance affects high-frequency noise filtering and transient response in RF-coupled protection circuits.

Can BZX84C3V9-7-F replace a 3.3 V Zener in a voltage reference circuit?

No-it is not a drop-in replacement. The BZX84C3V9-7-F has a nominal Zener voltage of 3.9 V (3.7–4.1 V), whereas a 3.3 V Zener (e.g., BZX84C3V3) regulates at 3.3 V (3.1–3.5 V). Substituting it would raise the reference point by ~0.6 V, causing overvoltage in feedback loops or incorrect sensor biasing unless resistor values are recalculated and system tolerance margins are re-verified.

Is the SOT23 pinout of BZX84C3V9-7-F compatible with common Zener footprints like DO-35 or SOD-123?

No-SOT23 is a 3-pin surface-mount package with standardized pin 1 (anode), pin 2 (cathode), and pin 3 (non-functional thermal pad); DO-35 is axial-lead through-hole, and SOD-123 is 2-pin SMT with reversed polarity marking. Mechanical and solder-pad layout are incompatible; board redesign is required for substitution, and polarity must be verified using the cathode band marking per top-view diagram in DS18001.