onsemi SZMMBZ5231BLT1

Overview

SZMMBZ5231BLT1 from onsemi is a 5.1 V, 225 mW surface-mount Zener diode in SOT-23 package, designed for precision voltage regulation and overvoltage protection in space-constrained circuits. It delivers ±5% Zener voltage tolerance at 20 mA test current, exhibits 17 Ω dynamic impedance, and supports ≤5 µA leakage at 2 V reverse bias - enabling stable reference generation in portable power rails and I/O protection networks.

For engineers reviewing the SZMMBZ5231BLT1 datasheet, pinout, applications, or equivalent options, key selection criteria include its AEC-Q101 qualification, 16 kV HBM ESD rating, Pb-free SOT-23 footprint, and verified performance across −65°C to +150°C junction temperature range.

Technical Context

This device operates as a two-terminal voltage reference with cathode-anode polarity and no internal connection on pin 2. Its Zener breakdown mechanism provides stable reverse conduction at nominal 5.1 V with low temperature coefficient (≈+2 mV/°C near 5 V), making it suitable for biasing, clamping, and threshold detection where moderate accuracy and thermal stability are required.

It is rated for 225 mW dissipation on FR-5 board with 556°C/W junction-to-ambient thermal resistance, and supports forward conduction up to 10 mA at ≤0.95 V drop. The SOT-23 package enables automated placement while maintaining compatibility with standard reflow profiles (260°C/10 s max).

Key Specifications

Pinout & Package

Package: SOT-23 (Case 318, Style 8), surface-mount plastic case with corrosion-resistant finish; cathode indicated by band; UL 94 V-0 flammability rating.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SZMMBZ5231BLT1, BZX84-C5V1 offers higher power but poorer regulation stiffness, while MMSZ5231BT1G delivers superior impedance and headroom at the cost of larger thermal footprint - choice depends on whether precision, surge capacity, or layout density dominates the design priority.

Availability

SZMMBZ5231BLT1 is available at Aetrix Electronics and suitable for automotive sensor interfaces, USB port protection circuits, and portable device power rail clamping requiring stable component supply and AEC-Q101 compliance.

Supply support for SZMMBZ5231BLT1 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 silicon solutions for automotive, industrial, cloud, and IoT applications - focused on enabling sustainable technology infrastructure.

SZMMBZ5231BLT1 belongs to the MMBZ52xxBLT1/SZMMBZ52xxBLT1G Zener regulator family, engineered for compact, reliable voltage reference and protection in high-density, thermally demanding environments.

FAQ

What is the Zener voltage tolerance of SZMMBZ5231BLT1?

The SZMMBZ5231BLT1 has a Zener voltage range of 4.84 V to 5.36 V at 20 mA test current, corresponding to ±5% tolerance around the nominal 5.1 V rating. This tolerance is guaranteed across operating temperature and lifetime, and is measured under pulse conditions to avoid self-heating effects - critical for repeatable reference design in SZMMBZ5231BLT1-based circuits.

Is SZMMBZ5231BLT1 suitable for automotive applications?

Yes, SZMMBZ5231BLT1 is AEC-Q101 qualified and PPAP capable, with full traceability and process controls meeting automotive reliability standards. Its −65°C to +150°C junction temperature range, 16 kV HBM ESD rating, and Pb-free SOT-23 package make it appropriate for engine control units, body electronics, and ADAS sensor modules where SZMMBZ5231BLT1 serves as a robust voltage clamp or bias reference.

What is the function of pin 2 on SZMMBZ5231BLT1?

Pin 2 of SZMMBZ5231BLT1 is a no-connect (NC) terminal - internally unconnected and electrically isolated. It must remain floating in PCB layout and should never be tied to ground, supply, or any other net. This mechanical pin provides structural support and alignment in the SOT-23 package but contributes no electrical function in the SZMMBZ5231BLT1 device.

How does the thermal resistance of SZMMBZ5231BLT1 affect its power handling?

SZMMBZ5231BLT1 has a junction-to-ambient thermal resistance (R_JA) of 556°C/W on FR-5 board, meaning each 225 mW of dissipated power raises junction temperature by ~125°C above ambient. This limits continuous DC operation to derated conditions above 25°C - for example, only ~150 mW at 50°C ambient. Designers must consider this when using SZMMBZ5231BLT1 in sustained clamp or regulation roles.

Can SZMMBZ5231BLT1 be used in forward-bias mode?

Yes, SZMMBZ5231BLT1 supports forward conduction with ≤0.95 V drop at 10 mA, making it usable as a low-voltage clamp or level translator. However, its primary design intent is reverse-bias Zener operation; forward characteristics are secondary and not optimized for switching or rectification. Applications relying on forward conduction should verify voltage drop and thermal behavior in the target SZMMBZ5231BLT1 circuit context.