Diodes Incorporated MMBZ5259BW-7

Overview

MMBZ5259BW-7 from Diodes Incorporated is a 39 V, 200 mW surface-mount Zener diode in SOT323 package, rated for ±2.5% zener voltage tolerance at 3.2 mA test current, with 80 Ω maximum zener impedance at 1 kHz and 0.1 μA reverse leakage at 30 V. It serves as a precision voltage reference or overvoltage clamp in low-power analog signal conditioning circuits.

For engineers reviewing the MMBZ5259BW-7 datasheet, MMBZ5259BW-7 pinout, MMBZ5259BW-7 application, or MMBZ5259BW-7 equivalent, key selection criteria include nominal zener voltage (39 V), power rating (200 mW), zener impedance (80 Ω), reverse leakage (0.1 μA @ 30 V), and AEC-Q101 qualification for automotive-grade reliability.

Technical Context

This Zener diode operates in reverse breakdown to maintain stable voltage regulation under controlled current conditions. Its 39 V nominal zener voltage is specified at I_ZT = 3.2 mA, with dynamic impedance measured at 1 kHz, and exhibits ≤0.1 μA reverse leakage at VR = 30 V - confirming tight leakage control for low-current bias networks.

The device uses an alloy-42 leadframe with matte tin plating, qualified to AEC-Q101, and features a green molding compound compliant with halogen/antimony-free requirements (<900 ppm Br, <900 ppm Cl, <1000 ppm Sb). Thermal resistance R_θJA is 625 °C/W on FR4 board per recommended pad layout.

Key Specifications

Pinout & Package

Package: SOT323 - ultra-small plastic surface-mount case (2.10 mm × 1.30 mm × 0.90 mm), molded with halogen/antimony-free "Green" compound, UL 94V-0 rated, moisture sensitivity level 1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BZX384-B39 and 1SMA5927BT3G, MMBZ5259BW-7 offers optimal balance of AEC-Q101 reliability, ultra-compact SOT323 size, and low-leakage performance - making it preferred for automotive and portable medical designs where board area and quiescent current are critical.

Availability

MMBZ5259BW-7 is available at Aetrix Electronics and suitable for automotive sensor modules, industrial analog input protection circuits, portable medical instrumentation, and consumer power supply feedback networks requiring stable component supply and full traceability.

Supply support for MMBZ5259BW-7 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 the Americas.

The MMBZ52xxBW series belongs to Diodes' AEC-Q101-qualified Zener diode portfolio, engineered specifically for automotive and industrial applications demanding high reliability, low leakage, and consistent voltage regulation in compact surface-mount packages.

FAQ

What is the maximum allowable continuous reverse voltage for MMBZ5259BW-7?

The absolute maximum reverse voltage is defined by its 39 V nominal zener voltage with ±2.5% tolerance (37.05–40.95 V), and operation beyond 40.95 V risks uncontrolled breakdown. The device is not rated for sustained reverse bias above its specified zener voltage - it must be operated in regulated reverse conduction with current limited to ≤3.2 mA for stable voltage reference use.

Does MMBZ5259BW-7 require external current-limiting resistors in shunt regulator configurations?

Yes - a series current-limiting resistor is mandatory to restrict zener current to ≤3.2 mA at worst-case input voltage. For example, with a 48 V supply and 39 V output, a minimum 2.8 kΩ resistor ensures safe operation. Without this resistor, excessive power dissipation (>200 mW) will cause thermal failure.

Is the SOT323 package of MMBZ5259BW-7 compatible with standard reflow soldering profiles?

Yes - the SOT323 package is qualified for Pb-free reflow per JEDEC J-STD-020D Level 1 moisture sensitivity. It supports peak temperatures up to 260°C and is compatible with standard SnAgCu (SAC305) reflow profiles, provided the recommended pad layout (AP02001) is followed to ensure thermal reliability and solder joint integrity.

How does the 0.1 μA reverse leakage at 30 V impact high-impedance circuit accuracy?

At 0.1 μA, leakage introduces ≤3 mV error in a 30 kΩ Thevenin-equivalent impedance network - well within 0.1% accuracy for most precision references. This low leakage makes MMBZ5259BW-7 suitable for biasing op-amp input stages, ADC reference dividers, and sensor excitation circuits where input bias currents must remain below 100 nA.