Diodes Incorporated MMBZ5242B-7-F

Overview

MMBZ5242B-7-F from Diodes Incorporated is a 12 V, ±5% tolerance, 350 mW surface-mount Zener diode in SOT23 package, optimized for voltage regulation and overvoltage protection in low-power analog and digital circuits, with 30 Ω dynamic impedance at 20 mA test current and 1.0 µA reverse leakage at 9.1 V.

For engineers reviewing the MMBZ5242B-7-F datasheet, MMBZ5242B-7-F pinout, MMBZ5242B-7-F application, or MMBZ5242B-7-F equivalent, this part serves as a precision reference and clamping device in power supply feedback loops, I/O line protection, and sensor biasing where stable 12 V regulation under 20 mA is required.

Technical Context

This Zener diode operates in reverse breakdown mode with a nominal zener voltage of 12.0 V (11.4–12.6 V range), specified at 20 mA test current (IZT). Its 30 Ω zener impedance (ZZT) ensures tight regulation under moderate load variation, while its 600 Ω knee impedance (ZZK) at 0.25 mA supports stable operation down to microamp-level bias currents.

The device uses planar die construction on FR-4 PCBs, delivering 350 mW power dissipation and a thermal resistance of 357 °C/W. It is fully RoHS-compliant, halogen- and antimony-free, and qualified to JEDEC high-reliability standards - suitable for industrial and consumer applications but not AEC-Q qualified unless marked with Q-suffix.

Key Specifications

Pinout & Package

MMBZ5242B-7-F is housed in a standard SOT23 plastic package (JEDEC TO-236AB), with three terminals: Anode (Pin 1), Cathode (Pin 2), and no internal connection (Pin 3). The cathode is marked by a band on the package top view.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BZX84-C12LT1G and MMBZ5242BS-7-F, MMBZ5242B-7-F offers optimal balance of regulation precision at 20 mA, industry-standard SOT23 footprint, and proven manufacturability in high-volume automated assembly - making it preferred for cost-sensitive, medium-power regulation tasks.

Availability

MMBZ5242B-7-F is available at Aetrix Electronics and suitable for power supply feedback networks, I/O protection circuits, sensor biasing, and reference voltage generation requiring stable component supply and full traceability.

Supply support for MMBZ5242B-7-F 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.

This part belongs to the MMBZ52xxB family of 350 mW Zener diodes designed specifically for compact, high-reliability voltage regulation and clamping in consumer, industrial, and computing applications - emphasizing planar consistency, RoHS compliance, and SMT manufacturability.

FAQ

What is the maximum continuous Zener current for MMBZ5242B-7-F at 25°C?

The device is rated for 350 mW power dissipation at 25°C ambient. At 12 V nominal Zener voltage, this corresponds to a maximum continuous Zener current of approximately 29 mA (350 mW ÷ 12 V). Derating begins above 25°C per the published power derating curve (Fig. 1), reaching zero at ~150°C.

Is MMBZ5242B-7-F suitable for automotive applications?

No - MMBZ5242B-7-F is not AEC-Q qualified. Diodes Incorporated offers automotive-grade equivalents with Q-suffix (e.g., MMBZ5242BQ-7-F), which undergo PPAP, are manufactured in IATF 16949-certified facilities, and meet AEC-Q200 stress testing requirements. This standard version is intended for industrial and commercial use only.

How does the 30 Ω Zener impedance affect regulation performance?

A 30 Ω dynamic impedance at 20 mA means that a ±10 mA change in Zener current results in approximately ±0.3 V change in output voltage. This enables stable regulation in feedback loops where load or supply variations cause modest current shifts, especially when combined with the tight 11.4–12.6 V tolerance band.

Can Pin 3 of the SOT23 package be grounded or left floating?

Pin 3 is internally unconnected (NC) and must remain electrically floating - neither grounded nor tied to any signal. Connecting it risks unintended parasitic paths or mechanical stress on bond wires. PCB layout should omit copper under Pin 3 and avoid solder mask openings that could cause bridging.