Taiwan Semiconductor Corporation BZX585B18

Overview

BZX585B18 from Taiwan Semiconductor is a surface-mount Zener diode with nominal zener voltage 18 V (±2%), 200 mW power dissipation, 45 Ω dynamic impedance at 5 mA test current, and SOD-523F package. It provides precision voltage regulation in low-power signal conditioning and reference circuits across industrial and consumer electronics.

For engineers reviewing the BZX585B18 datasheet, BZX585B18 pinout, BZX585B18 application, or BZX585B18 equivalent, key selection criteria include zener tolerance (±2%), thermal resistance (212 °C/W), reverse leakage (<0.045 µA at 12.6 V), temperature coefficient (+12.4 mV/°C), and MSL-1 moisture sensitivity rating.

Technical Context

The BZX585B18 operates as a two-terminal voltage reference device, conducting in reverse breakdown to clamp or regulate voltage at 18 V with tight 2% initial tolerance. Its zener impedance of 45 Ω at I_ZT = 5 mA ensures stable regulation under moderate load variations.

Designed for ambient temperatures up to +150 °C and junction temperatures to +150 °C, it features halogen-free epoxy, Pb-free/RoHS compliance, and high-temperature soldering capability (260 °C/10 s). The SOD-523F package enables high-density PCB layouts with minimal footprint (0.7–0.9 mm × 1.5–1.7 mm).

Key Specifications

Pinout & Package

SOD-523F is a two-terminal surface-mount package with anode and cathode marked by polarity band. Total weight is approximately 1.36 mg. Moisture Sensitivity Level is 1 (unlimited floor life at ≤30 °C/60% RH).

Key Features

Applications

Equivalent & Alternatives

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

Compared with BZX585B18, MMBZ5245BS-7-F offers greater power headroom but sacrifices precision and thermal efficiency; BZX384-B18 matches tolerance and MSL but requires more PCB area and delivers less thermal performance per unit volume.

Availability

BZX585B18 is available at Aetrix Electronics and suitable for industrial sensor interfaces, USB-C power delivery subsystems, automotive cabin controls, and IoT battery monitoring systems requiring stable component supply and long-term sourcing continuity.

Supply support for BZX585B18 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 semiconductor manufacturer specializing in discrete devices, analog ICs, and power management solutions for industrial, computing, and consumer markets.

The BZX585B18 belongs to TSC's Small Signal Product line of precision Zener diodes engineered for high-reliability voltage reference and clamping in space-constrained, thermally demanding applications.

FAQ

What is the zener voltage tolerance of BZX585B18?

The BZX585B18 has a nominal zener voltage of 18 V with a guaranteed tolerance of ±2%, meaning the actual breakdown voltage falls between 17.64 V and 18.36 V when tested at 5 mA. This tight tolerance is confirmed in the Electrical Characteristics table of the official Taiwan Semiconductor datasheet (Version C1607) and supports high-accuracy reference designs without post-production trimming. The BZX585B18 achieves this via laser-trimmed silicon process control.

Is BZX585B18 suitable for lead-free reflow soldering?

Yes, BZX585B18 is qualified for high-temperature lead-free reflow with guaranteed performance after exposure to 260 °C for 10 seconds - exceeding JEDEC J-STD-020 requirements. Its SOD-523F package uses halogen-free molding compound and Pb-free terminations compliant with RoHS Directive 2011/65/EU. The BZX585B18 maintains electrical parameters within spec after such thermal stress, as verified in Taiwan Semiconductor's reliability testing reports.

What is the maximum reverse leakage current for BZX585B18?

The maximum reverse leakage current (I_R) for BZX585B18 is 0.045 µA at 12.6 V, as specified in the Electrical Characteristics table. This ultra-low leakage is measured at room temperature and ensures minimal loading on high-impedance reference dividers or battery-monitoring circuits. The BZX585B18 maintains this performance across its rated storage temperature range (–65 °C to +150 °C), supporting long-life deployments in energy-sensitive applications.

Does BZX585B18 have a defined temperature coefficient?

Yes, BZX585B18 has a positive temperature coefficient of +12.4 mV/°C at I_ZT = 5 mA, meaning its zener voltage increases by approximately 12.4 mV per degree Celsius rise in junction temperature. This value is explicitly listed in the datasheet's Electrical Characteristics section and enables predictable thermal drift modeling in precision reference circuits. The BZX585B18's coefficient is stable and repeatable due to its optimized doping profile and planar junction structure.

What packaging format is used for BZX585B18?

BZX585B18 is supplied in 7-inch reels containing 8,000 units per reel, using standard tape-and-reel packaging compatible with high-speed SMT placement equipment. The SOD-523F package features green compound and complies with JEDEC standards for pitch (0.65 mm), cavity depth, and carrier tape specifications. Each reel includes traceable lot marking, and the BZX585B18's MSL-1 rating means no dry-pack or baking is required before assembly.