Nexperia USA Inc. BZX84W-C3V9-QX

Overview

BZX84W-C3V9-QX from Nexperia is a ±5% tolerance Zener voltage regulator diode in SOT323 (SC-70) package, rated for 3.9 V nominal breakdown voltage at 5 mA, 275 mW total power dissipation, and qualified to AEC-Q101 for automotive use. It provides stable reference voltage in low-power biasing, overvoltage clamping, and signal conditioning circuits.

For engineers reviewing the BZX84W-C3V9-QX datasheet, BZX84W-C3V9-QX pinout, BZX84W-C3V9-QX application, or BZX84W-C3V9-QX equivalent, key selection criteria include Zener voltage tolerance (±5%), low reverse leakage (3 µA at VR = 1 V), differential resistance (90 Ω at IZ = 5 mA), temperature coefficient (−2.5 mV/K), and AEC-Q101 qualification for harsh-environment reliability.

Technical Context

This Zener diode operates in reverse-biased breakdown mode with a tightly controlled 3.9 V nominal Zener voltage at 5 mA test current. Its −2.5 mV/K temperature coefficient ensures predictable drift across −55 °C to +150 °C ambient range, and its 90 Ω differential resistance supports stable regulation under moderate load variation.

Designed for surface-mount use on FR4 PCBs with single-sided copper, it delivers 275 mW continuous power dissipation and withstands non-repetitive peak reverse power up to 40 W (tp = 100 µs). The SOT323 package enables high-density placement while maintaining thermal performance via 455 K/W junction-to-ambient thermal resistance.

Key Specifications

Pinout & Package

SOT323 (SC-70) leadless surface-mount plastic package: 1.35 mm × 1.75 mm footprint, 0.95 mm height, 3-terminal configuration with gull-wing leads.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BZX84W-B3V9-Q, this part trades voltage accuracy for cost and availability; versus MMSZ4685T1G, it sacrifices power rating for miniaturization-making BZX84W-C3V9-QX optimal for space-constrained automotive and portable electronics requiring AEC-Q101 compliance.

Availability

BZX84W-C3V9-QX is available at Aetrix Electronics and suitable for automotive body electronics, industrial sensor interfaces, and portable medical device power management requiring stable component supply, AEC-Q101 traceability, and SOT323 footprint compatibility.

Supply support for BZX84W-C3V9-QX 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

Nexperia is a global semiconductor expert focused on high-volume, high-reliability discrete and logic devices, with leadership in automotive-qualified components and advanced packaging.

The BZX84W-Q series belongs to Nexperia's AEC-Q101-qualified Zener diode product line, engineered specifically for robust voltage regulation in automotive subsystems and industrial controls operating across extended temperature ranges.

FAQ

What is the maximum continuous reverse current this Zener can handle at 3.9 V?

The BZX84W-C3V9-QX is not rated for continuous reverse conduction at its Zener voltage. Its absolute maximum reverse current is limited by power dissipation: at 3.9 V, the theoretical max DC current is 70.5 mA (275 mW ÷ 3.9 V), but derating per thermal resistance and ambient temperature is required. For reliable operation, design for ≤20 mA at 25 °C ambient with adequate PCB copper area.

Does the 'n.c.' pin require grounding or floating in PCB layout?

Pin 2 is internally not connected and must remain electrically floating-no solder mask opening, no copper pour, and no trace connection. Connecting it risks mechanical stress on the die bond or unintended parasitic coupling. The SOT323 footprint drawing explicitly defines this terminal as non-functional and isolated.

How does the −2.5 mV/K temperature coefficient affect regulation accuracy over temperature?

At 3.9 V nominal, a −2.5 mV/K coefficient causes ~−0.25 V drift from 25 °C to 125 °C ambient (100 K × −2.5 mV/K), resulting in ~3.65 V output. This is within the ±5% tolerance band (3.7–4.1 V) and predictable for compensation in closed-loop systems, but unsuitable for applications requiring <±1% stability without external correction.

Can this Zener replace a 3.3 V type in an existing circuit?

No-BZX84W-C3V9-QX has a nominal 3.9 V Zener voltage, not 3.3 V. Substituting it would raise clamping/reference voltage by 0.6 V, potentially exceeding downstream IC absolute maximum ratings or violating signal-level specifications. Use BZX84W-C3V3-Q (3.3 V, ±5%) for direct replacement with matching voltage and tolerance.