Taiwan Semiconductor Corporation BZX85C18

Overview

BZX85C18 from Taiwan Semiconductor is a 1.3W, ±5% tolerance Zener diode with nominal breakdown voltage of 18 V, designed for precision voltage regulation and reference in low-power DC circuits. It operates across -65°C to +200°C junction temperature range, features hermetically sealed DO-41 glass package, and is used in on-board DC/DC converters and lighting applications.

For engineers reviewing the BZX85C18 datasheet, BZX85C18 pinout, BZX85C18 application, or BZX85C18 equivalent, key selection criteria include its 18 V nominal Zener voltage (16.8–19.1 V range), 20 mA test current, 500 Ω maximum Zener impedance at IZT, 0.5 mA leakage current at 13 V reverse bias, and DO-41 mechanical compatibility with standard through-hole PCB layouts.

Technical Context

The BZX85C18 functions as a single-die, silicon planar Zener diode operating in reverse breakdown mode. Its voltage regulation relies on controlled avalanche and Zener mechanisms, with specified Zener impedance measured under 10 ms pulse conditions and AC-derived impedance per 10% RMS superimposed current.

It is rated for 1.3 W steady-state power dissipation at 25°C ambient, with thermal resistance of 130°C/W junction-to-ambient. The device uses pure tin-plated leads compliant with J-STD-002 solderability standards and features cathode band polarity marking.

Key Specifications

Pinout & Package

Package: DO-41 glass axial lead package with cathode band marking; 2.8 mm diameter body, 5.2 mm length, 0.86 mm lead diameter, RoHS-compliant pure tin plating.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 1N4746A and MMSZ5246B, the BZX85C18 offers higher power dissipation (1.3 W) in the industry-standard DO-41 through-hole package, making it suitable for legacy designs and thermally demanding linear regulation tasks where SMT alternatives lack sufficient thermal mass or power margin.

Availability

BZX85C18 is available at Aetrix Electronics and suitable for low-voltage stabilizers, on-board DC/DC converters, and lighting applications requiring stable component supply with full traceability and long-lifecycle support.

Supply support for BZX85C18 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

Taiwan Semiconductor Corporation (TSC) is a vertically integrated analog and discrete semiconductor manufacturer headquartered in Hsinchu, Taiwan, serving global industrial, computing, and consumer markets since 1979.

The BZX85C series belongs to TSC's general-purpose Zener diode product line, engineered for cost-effective, high-reliability voltage reference and clamping in mainstream power management circuits.

FAQ

What is the nominal Zener voltage and tolerance of BZX85C18?

The BZX85C18 has a nominal Zener voltage of 18 V with a standard tolerance of ±5%, corresponding to a guaranteed breakdown range of 16.8 V to 19.1 V at 20 mA test current. This tolerance is confirmed in the Electrical Specifications table of the Taiwan Semiconductor datasheet Version H2301 and applies under standard 10 ms pulse test conditions.

What package type does BZX85C18 use and what are its key mechanical features?

BZX85C18 uses the DO-41 glass axial package with cathode band marking, 2.8 mm body diameter, and pure tin-plated leads compliant with J-STD-002 solderability. Its mechanical outline matches industry-standard DO-41 footprints, enabling drop-in replacement in existing through-hole designs without layout changes.

What is the maximum power dissipation and thermal resistance of BZX85C18?

BZX85C18 has a maximum power dissipation (P_D) of 1.3 W at 25°C ambient temperature and a junction-to-ambient thermal resistance (R_θJA) of 130°C/W. These values are specified in the Absolute Maximum Ratings and Thermal Performance sections of the official datasheet and define safe continuous operation limits under natural convection cooling.

How does BZX85C18 perform in terms of Zener impedance and leakage current?

BZX85C18 exhibits a maximum Zener impedance (Z_ZT) of 500 Ω at 20 mA test current and a maximum leakage current (I_R) of 0.5 µA at 13 V reverse bias. These parameters directly impact regulation accuracy and standby power loss, making BZX85C18 suitable for precision reference and low-leakage clamping applications.

Is BZX85C18 RoHS compliant and what is its junction temperature range?

Yes, BZX85C18 is RoHS compliant with green compound encapsulation and pure tin-plated leads. Its junction temperature range spans –65°C to +200°C, supporting operation in extreme environments such as automotive under-hood systems and industrial motor controls where thermal robustness is critical.