onsemi SZBZX84C18ET1G

Overview

SZBZX84C18ET1G from onsemi is a 250 mW surface-mount Zener diode in SOT-23 package, providing precise 18 V reverse breakdown regulation at 5 mA test current (16.8–19.1 V range), with 45 Ω dynamic impedance and 0.05 µA max reverse leakage at 14.4 V. It serves as a voltage reference or overvoltage clamp in portable power rails and signal conditioning circuits.

For engineers reviewing the SZBZX84C18ET1G datasheet, pinout, applications, or equivalent options, key selection criteria include Zener voltage tolerance, temperature coefficient (+12.6 mV/°C), junction-to-ambient thermal resistance (500 °C/W on FR-5), ESD rating (>16 kV HBM), and SOT-23 footprint compatibility.

Technical Context

This device operates as a two-terminal voltage reference using avalanche breakdown in silicon PN junction. Its nominal 18 V Zener voltage is specified at I_ZT = 5 mA, with guaranteed min/max limits and measured temperature coefficient of +12.6 mV/°C - indicating positive drift with rising temperature.

The SOT-23 package features three terminals: anode (Pin 1), no connection (Pin 2), and cathode (Pin 3); it supports automated placement and reflow soldering per JEDEC J-STD-020, with 260 °C maximum soldering temperature for 10 seconds.

Key Specifications

Pinout & Package

SOT-23 (TO-236) plastic surface-mount package, 2.90 × 1.30 × 1.00 mm, void-free thermosetting case with corrosion-resistant finish and UL 94 V-0 flammability rating. Cathode identified by polarity band.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BZX84C18ET1G, SZBZX84C18ET1G adds AEC-Q101 qualification and PPAP support for automotive programs, while MMSZ4687T1G offers double the power rating and lower impedance for demanding transient suppression - neither is pin-compatible due to differing internal construction and thermal design.

Availability

SZBZX84C18ET1G is available at Aetrix Electronics and suitable for battery management systems, USB interface protection, industrial sensor signal chains, and automotive cabin electronics requiring stable component supply and long-term lifecycle assurance.

Supply support for SZBZX84C18ET1G 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

onsemi is a global semiconductor supplier delivering energy-efficient, intelligent power and sensing solutions for automotive, industrial, cloud, medical, and IoT applications.

The BZX84CxxxET1G/SZBZX84CxxxET1G series targets compact, reliable voltage regulation in space-constrained portable and automotive electronics, emphasizing low-profile packaging, high ESD immunity, and AEC-Q101 compliance where required.

FAQ

What is the Zener voltage tolerance of SZBZX84C18ET1G at 5 mA test current?

The SZBZX84C18ET1G has a guaranteed Zener voltage range of 16.8 V to 19.1 V when tested at I_ZT = 5 mA and T_A = 25 °C. This ±1.1 V tolerance reflects manufacturing variation and ensures predictable regulation performance across production lots. The nominal 18 V value is the center point used for design calculations, but circuit margins must accommodate the full min/max span. SZBZX84C18ET1G maintains this specification under standard JEDEC test conditions.

Is SZBZX84C18ET1G suitable for automotive applications?

Yes, SZBZX84C18ET1G is AEC-Q101 qualified and PPAP capable, making it suitable for automotive applications including body control modules, infotainment power supplies, and sensor interfaces. The "SZ" prefix denotes automotive-grade process controls, site-specific change management, and extended reliability testing beyond commercial-grade equivalents like BZX84C18ET1G. SZBZX84C18ET1G operates across −65 °C to +150 °C junction temperature range, supporting under-hood and cabin environments.

What is the thermal resistance of SZBZX84C18ET1G on FR-5 board?

The junction-to-ambient thermal resistance (R_JA) of SZBZX84C18ET1G is 500 °C/W when mounted on FR-5 board per datasheet Note 2. This value assumes standard 1.0 × 0.75 × 0.62 inch board dimensions and defines the temperature rise per watt dissipated. At its 250 mW rating, this yields a 125 °C rise above ambient - requiring careful thermal design in enclosed or high-temperature environments. SZBZX84C18ET1G derates linearly above 25 °C ambient at 2.0 mW/°C.

Does SZBZX84C18ET1G have a functional Pin 2 connection?

No, Pin 2 of SZBZX84C18ET1G is internally unconnected (NC) and must remain floating in the PCB layout. The device uses only Pins 1 (anode) and 3 (cathode) for electrical operation; Pin 2 serves no circuit function and is a structural feature of the SOT-23 leadframe. Connecting Pin 2 to any net may cause unintended parasitic paths or assembly defects. SZBZX84C18ET1G pinout is explicitly defined as 1-Anode, 2-No Connection, 3-Cathode in the official onsemi datasheet.

How does the temperature coefficient affect SZBZX84C18ET1G's regulation accuracy?

The SZBZX84C18ET1G exhibits a +12.6 mV/°C temperature coefficient at I_ZT = 5 mA, meaning its Zener voltage increases by approximately 12.6 mV for every 1 °C rise in junction temperature. Over a −40 °C to +125 °C range, this contributes up to ±2.08 V drift relative to 25 °C nominal, directly impacting reference stability. Designers must account for this in precision applications using thermal modeling or compensation techniques. SZBZX84C18ET1G's positive tempco is typical for 18 V Zeners in this family.