onsemi MMBZ5237B

Overview

MMBZ5237B from Fairchild Semiconductor is a 5% tolerance, 8.2 V Zener diode in SOT-23 package, rated for 350 mW power dissipation, with 8.0 Ω dynamic impedance at 20 mA test current and 6.5 µA reverse leakage at 6.5 V, used for precision voltage regulation and overvoltage protection in low-power analog circuits.

For engineers reviewing the MMBZ5237B datasheet, pinout, applications, or equivalent options, key selection criteria include Zener voltage tolerance, dynamic impedance at specified test current, reverse leakage at rated VR, thermal stability across -55°C to +150°C, and SOT-23 footprint compatibility with space-constrained PCB layouts.

Technical Context

The MMBZ5237B operates as a silicon planar Zener diode optimized for stable voltage reference and clamping functions in biasing, feedback, and protection circuits. It exhibits a nominal Zener voltage of 8.2 V with ±5% tolerance and maintains regulation within ±0.1 V over temperature range -55°C to +125°C per typical characteristics.

Its 8.0 Ω dynamic impedance at IZ = 20 mA ensures low output impedance under regulation, while forward voltage remains ≤0.9 V at IF = 10 mA. Absolute maximum ratings specify 150°C junction temperature and 350 mW power dissipation under TA = 25°C conditions.

Key Specifications

Pinout & Package

SOT-23 surface-mount package with three terminals: anode (Pin 1), cathode (Pin 2), and no-connect (Pin 3). Pin 3 is internally unconnected and must remain floating or grounded per layout guidelines.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BZX84-C8V2 and MMBZ5237BS, the MMBZ5237B delivers superior regulation stiffness (8.0 Ω vs. 10 Ω) and higher power headroom (350 mW vs. 300 mW or thermally limited SOD-323), making it preferred for stable biasing and feedback in industrial-grade analog circuits.

Availability

MMBZ5237B is available at Aetrix Electronics and suitable for power supply feedback, overvoltage clamp, and bias network stabilization requiring stable component supply and consistent parametric performance across production lots.

Supply support for MMBZ5237B 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

Fairchild Semiconductor was a U.S.-based semiconductor company specializing in power management, analog, and discrete components before its acquisition by ON Semiconductor in 2016.

The MMBZ52xxB series was designed for compact, high-reliability voltage reference and protection in space-constrained consumer, computing, and industrial electronics.

FAQ

What is the Zener voltage tolerance of MMBZ5237B?

The MMBZ5237B has a Zener voltage tolerance of ±5% at 8.2 V, meaning its actual breakdown voltage falls between 7.79 V and 8.61 V under standard test conditions (TA = 25°C, IZ = 20 mA). This tolerance is guaranteed per the Fairchild MMBZ5221B–MMBZ5257B datasheet Rev. A2 and applies to all units in the production lot. The MMBZ5237B maintains this specification across its full operating temperature range.

What is the maximum power dissipation for MMBZ5237B?

The MMBZ5237B has a maximum power dissipation (PD) of 350 mW at TA = 25°C, as defined in the Absolute Maximum Ratings table. Derating is required above 25°C ambient-typically 2.33 mW/°C-for safe operation up to TJ = +150°C. This rating assumes proper PCB copper area for heat sinking and applies to continuous DC operation; pulsed conditions require consultation with the manufacturer per Note 2 in the datasheet.

Does MMBZ5237B have a no-connect pin, and how should it be handled?

Yes, MMBZ5237B uses a 3-pin SOT-23 package where Pin 3 is designated NC (no connect). It is internally unconnected and must not be electrically tied to any net, ground, or power plane. Leaving Pin 3 floating is mandatory; soldering it to a trace or pad may introduce parasitic coupling or mechanical stress that affects long-term reliability. The MMBZ5237B connection diagram explicitly confirms Pin 3 as NC in the original Fairchild documentation.

What is the forward voltage specification for MMBZ5237B?

The forward voltage (VF) of MMBZ5237B is specified as ≤0.9 V at IF = 10 mA, consistent across the entire MMBZ5200 series. This parameter is measured under forward-biased conditions and confirms suitability for dual-use roles such as polarity indication or low-drop rectification in auxiliary circuits. The MMBZ5237B's VF remains stable across temperature and matches the absolute maximum rating structure defined in the Fairchild datasheet.

How does MMBZ5237B perform under temperature variation?

The MMBZ5237B exhibits typical Zener voltage drift of less than ±0.1 V over -55°C to +125°C, based on published temperature coefficient curves for adjacent devices in the family (e.g., 5.1 V and 12 V variants). Its TC is minimized through planar process optimization, supporting stable regulation in industrial environments. The MMBZ5237B's guaranteed operating junction temperature of +150°C further validates its thermal robustness in real-world applications.