Nexperia USA Inc. BZX84W-B18X

Overview

BZX84W-B18X from Nexperia is a ±2 % tolerance Zener voltage regulator diode in SOT323 (SC-70) package, rated for 18 V nominal Zener voltage at 5 mA, 275 mW total power dissipation, and 225 Ω differential resistance at I_Z = 5 mA - used for precision voltage reference and local regulation in space-constrained analog and power management circuits.

For engineers reviewing the BZX84W-B18X datasheet, BZX84W-B18X pinout, BZX84W-B18X application, or BZX84W-B18X equivalent, this page delivers verified electrical parameters, thermal behavior, real-world Zener stability data, and direct substitution guidance for low-power voltage clamping and reference design.

Technical Context

This Zener diode operates in reverse breakdown with a temperature coefficient of +14.4 mV/K at I_Z = 5 mA, indicating positive drift with junction temperature - critical for biasing stability in temperature-varying environments. Its 1.5 pF capacitance at 1 MHz and 0 V reverse bias enables use in high-frequency noise suppression without signal distortion.

The device features a non-repetitive peak reverse power dissipation of 40 W for 100 µs pulses and supports forward conduction up to 200 mA, allowing bidirectional transient handling in protection circuits. Thermal resistance from junction to ambient is 455 K/W on standard FR4 PCB, defining derating limits above 25 °C ambient.

Key Specifications

Pinout & Package

SOT323 (SC-70) leadless surface-mount plastic package: 1.35 mm × 1.75 mm footprint, 0.65 mm pitch, 0.9 mm height - optimized for automated placement and reflow soldering on dense PCBs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BZX84W-B18X, MMBZ5245B trades tighter board integration for higher power headroom, while BZX84-C18 sacrifices 0.8 % absolute voltage accuracy for lower unit cost - making BZX84W-B18X optimal for compact, precision-regulated designs where thermal and spatial constraints dominate.

Availability

BZX84W-B18X is available at Aetrix Electronics and suitable for precision voltage reference, overvoltage protection, and low-power bias generation requiring stable component supply across automotive infotainment subsystems, industrial sensor signal conditioning, and portable medical instrumentation.

Supply support for BZX84W-B18X 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 logic, discrete, and MOSFET solutions - headquartered in Nijmegen, Netherlands, with manufacturing in Asia and Europe.

The BZX84W series belongs to Nexperia's general-purpose Zener diode product line, engineered for stable voltage regulation in space-constrained consumer, industrial, and computing applications where SMT scalability and parametric consistency are critical.

FAQ

What is the maximum continuous Zener current for BZX84W-B18X at 70 °C ambient?

At 70 °C ambient, derating applies: P_tot drops linearly from 275 mW at 25 °C to zero at 150 °C. At 70 °C, allowable power is 212 mW. With V_Z ≈ 18 V, maximum continuous Zener current is 212 mW ÷ 18 V = 11.8 mA - confirmed by thermal resistance (455 K/W) and ambient-to-junction delta.

Does BZX84W-B18X support bidirectional ESD protection?

No - BZX84W-B18X is a unidirectional Zener diode with anode and cathode terminals. It conducts only in reverse breakdown (cathode positive) and forward bias (anode positive). For bidirectional ESD protection, a paired Zener or dedicated TVS array like PESD5V0S1BA must be used.

How does the 225 Ω differential resistance affect regulation accuracy under load?

At I_Z = 5 mA, a 1 mA load current change causes ΔV = 225 Ω × 1 mA = 225 mV shift. For an 18 V reference, that is 1.25 % deviation - acceptable for non-critical biasing but insufficient for high-precision DAC references without additional buffering or feedback.

Can BZX84W-B18X replace BZX84-C18 in existing designs?

Yes, electrically and mechanically - both use SOT323, share identical pinout and 18 V nominal voltage. However, BZX84W-B18X offers ±2 % tolerance versus ±5 % for BZX84-C18, improving worst-case regulation by ±0.8 V. No layout change is needed, but verify if tighter tolerance impacts downstream bias point stability.