Diodes Incorporated BZX84C18-7

Overview

BZX84C18-7 from Diodes Incorporated is a 350mW surface-mount Zener diode with nominal zener voltage 18V (16.8–19.1V range), 45Ω maximum zener impedance at 5mA test current, and ±0.1µA maximum reverse leakage at 12.6V. It operates from −65°C to +150°C and is used for precision voltage regulation in low-power analog supply rails and reference circuits.

For engineers reviewing the BZX84C18-7 datasheet, BZX84C18-7 pinout, BZX84C18-7 application, or BZX84C18-7 equivalent, key selection criteria include zener voltage tolerance, dynamic impedance at rated test current, thermal resistance (357°C/W), reverse leakage at VR = 12.6V, and SOT23 package compatibility with automated pick-and-place assembly.

Technical Context

This device functions as a two-terminal voltage reference by operating in reverse breakdown mode with controlled avalanche characteristics. Its planar die construction ensures stable zener voltage over temperature and time, and its 350mW power rating is valid under ambient-temperature terminal conditions per J-STD-020 Level 1 moisture sensitivity.

The zener voltage exhibits a positive temperature coefficient of +2.5mV/°C near 18V, enabling predictable drift compensation in bias networks. Reverse leakage remains ≤0.1µA up to 12.6V, supporting low-current sensing and standby-mode regulation in battery-powered systems.

Key Specifications

Pinout & Package

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

Key Features

Applications

Equivalent & Alternatives

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

Compared with MMBZ5245B-7-F, BZX84C18-7 offers lower thermal resistance for better power handling in confined spaces; compared with BZX84-C18,115, it provides faster replenishment for prototyping and low-volume builds without sacrificing performance.

Availability

BZX84C18-7 is available at Aetrix Electronics and suitable for voltage reference design, overvoltage protection, temperature-stable biasing, and low-power sensor excitation requiring stable component supply across automotive, industrial, and medical electronics programs.

Supply support for BZX84C18-7 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, headquartered in Plano, Texas, with design, manufacturing, and sales operations across Asia, Europe, and North America.

The BZX84 series belongs to Diodes' precision Zener diode product line, engineered for stable voltage regulation in space-constrained, high-reliability applications including automotive control units and industrial power supplies.

FAQ

What is the maximum reverse voltage (VR) this diode can withstand before breakdown?

The BZX84C18-7 has a specified maximum reverse current (IR) of ≤0.1µA at VR = 12.6V. Breakdown occurs at its nominal zener voltage of 18V (min 16.8V), meaning it begins regulating at approximately 16.8V and maintains regulation up to its power limit. Applying >19.1V continuously risks exceeding its 350mW dissipation limit unless current is strictly limited.

Is this part suitable for automotive applications?

Yes - BZX84C18-7 is qualified to AEC-Q101 standards for high-reliability automotive use. It meets requirements for thermal cycling, humidity resistance, and mechanical shock, and its −65°C to +150°C operating range covers under-hood and cabin environments. The "Q" suffix (e.g., BZX84C18Q-7-F) denotes the automotive-grade variant with additional traceability.

How does the SOT23 package affect thermal performance?

The SOT23 package delivers a thermal resistance of 357°C/W (junction-to-ambient) when terminals are held at ambient temperature. In real PCB layouts, thermal performance depends on copper area and via count: typical FR-4 mounting yields ~417°C/W. For sustained 350mW operation, ≥25mm² of 1oz copper connected to both anode and cathode pads is recommended to maintain junction temperature below 150°C.

Can this Zener diode replace a 1N4746A in existing designs?

No - the 1N4746A is a 3W through-hole Zener in DO-41 package, while BZX84C18-7 is a 350mW SOT23 surface-mount device. Though both have 18V nominal zener voltage, their power handling, thermal behavior, and package geometry differ fundamentally. Direct replacement requires verifying that peak power, thermal path, and board layout constraints are satisfied; redesign of thermal relief and current limiting is typically necessary.