Diodes Incorporated MMSZ5239BS-7

Overview

MMSZ5239BS-7 from Diodes Incorporated is a surface-mount Zener diode with a nominal zener voltage of 9.1 V (±5% tolerance), 200 mW power dissipation, and 10 Ω zener impedance at 20 mA test current. It features planar die construction in an SOD-323 package, optimized for voltage regulation and reference applications in space-constrained consumer and industrial PCBs.

For engineers reviewing the MMSZ5239BS-7 datasheet, MMSZ5239BS-7 pinout, MMSZ5239BS-7 application, or MMSZ5239BS-7 equivalent, key selection criteria include its 9.1 V breakdown voltage, low 10 Ω dynamic impedance, 3.0 µA reverse leakage at 7.0 V, thermal resistance of 625 °C/W, and compatibility with automated SMT assembly on FR-4 boards.

Technical Context

This Zener diode operates in reverse-biased breakdown mode to maintain stable voltage across load variations. Its 9.1 V nominal zener voltage is specified at 20 mA test current (IZT), with a tight ±5% tolerance (8.65–9.56 V) and maximum 10 Ω impedance at IZT, ensuring predictable regulation under moderate current loads.

Thermally, it delivers 200 mW power dissipation at 25°C ambient, derating linearly above 25°C per the 625 °C/W junction-to-ambient thermal resistance. The SOD-323 package supports reflow soldering per J-STD-020D Level 1 moisture sensitivity, with cathode band polarity marking and matte tin-plated Alloy 42 leads.

Key Specifications

Pinout & Package

Package: SOD-323 - ultra-compact surface-mount plastic case (2.30–2.70 mm length, 1.20–1.40 mm width, 0.25–0.35 mm height), UL 94V-0 rated, cathode indicated by band.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BZX584C9V1 and MMBZ5239BS, MMSZ5239BS-7 offers optimal balance of miniaturization (SOD-323), thermal performance (625 °C/W), and production readiness for high-volume SMT lines-making it preferred for new compact designs requiring reliable 9.1 V regulation without thermal compromise.

Availability

MMSZ5239BS-7 is available at Aetrix Electronics and suitable for USB power protection, microcontroller reset supervision, industrial sensor signal conditioning, and low-power IoT reference applications requiring stable component supply and full RoHS compliance.

Supply support for MMSZ5239BS-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, specializing in high-reliability, cost-optimized components for industrial, computing, and consumer markets.

The MMSZ52xxBS series targets general-purpose voltage regulation and reference needs in space-constrained applications, emphasizing manufacturability, consistency, and environmental compliance across automotive-qualified and commercial-grade variants.

FAQ

What is the maximum reverse voltage that can be continuously applied before breakdown?

The MMSZ5239BS-7 exhibits a sharp, well-defined breakdown at 9.1 V nominal, with guaranteed operation between 8.65 V and 9.56 V at 20 mA. Below 7.0 V, reverse leakage remains ≤3.0 µA-so continuous application of up to 7.0 V poses no risk of conduction or degradation. Exceeding 9.56 V risks uncontrolled current if not current-limited.

Can this Zener diode be used in series or parallel configurations?

Series connection is feasible for higher-voltage references (e.g., two MMSZ5239BS-7 units yield ~18.2 V), but mismatched tolerances may reduce overall accuracy. Parallel use is strongly discouraged-minor V_Z differences cause current hogging, thermal runaway, and premature failure due to the device's positive temperature coefficient above ~5 V.

Does the SOD-323 package support hand-soldering repair?

Yes-the SOD-323 package is compatible with fine-tip soldering irons and hot-air rework stations. Its 1.2–1.4 mm width and visible cathode band allow visual alignment; recommended preheating to 100°C and localized 320–350°C iron tip contact for ≤3 seconds prevents pad lifting or plastic damage per Diodes' AP02002 guidelines.

How does its zener impedance affect regulation in varying load conditions?

With Z_ZT = 10 Ω at 20 mA, a 5 mA load change produces only ~50 mV output shift (ΔV = Z_Z × ΔI). This enables stable regulation in circuits like ADC references or reset supervisors where <100 mV drift is acceptable. For tighter regulation, pair with a low-ESR capacitor or add series resistance to limit current swing.