Diodes Incorporated MMSZ5239B-7-F

Overview

MMSZ5239B-7-F from Diodes Incorporated is a 500mW surface-mount Zener diode with a nominal zener voltage of 9.1V (8.65–9.56V range), 20mA test current, and 10Ω zener impedance at 20mA. It features SOD123 packaging, cathode band polarity, and is qualified to AEC-Q101 for automotive reliability. It serves as a precision voltage reference or overvoltage clamp in low-power analog circuits.

For engineers reviewing the MMSZ5239B-7-F datasheet, MMSZ5239B-7-F pinout, MMSZ5239B-7-F application, or MMSZ5239B-7-F equivalent, this part is selected for stable 9.1V regulation in space-constrained PCBs where thermal derating, RoHS compliance, and automotive-grade qualification are critical design requirements.

Technical Context

This Zener diode operates in reverse breakdown mode to maintain a stable voltage across its terminals under varying load and temperature conditions. Its 9.1V nominal zener voltage exhibits a positive temperature coefficient (~0.06%/°C per Figure 6), and it delivers regulated output with ≤10Ω dynamic impedance at I_ZT = 20mA.

The device is rated for 370mW power dissipation at T_A = +25°C and derates linearly above +25°C with R_θJA = 338°C/W on FR-4 PCB. Maximum reverse leakage is 3.0μA at V_R = 7.0V, confirming tight low-current regulation capability.

Key Specifications

Pinout & Package

Package: SOD123 - molded plastic case with matte tin-plated alloy 42 leadframe, cathode band marking, and 0.01g mass. Moisture sensitivity level 1 per J-STD-020.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BZX584C9V1 and 1N4739A, MMSZ5239B-7-F uniquely balances automotive qualification, SOD123 manufacturability, and 370mW ambient-rated power-making it optimal for production-scale automotive and industrial surface-mount designs requiring AEC-Q101 compliance without sacrificing regulation precision.

Availability

MMSZ5239B-7-F is available at Aetrix Electronics and suitable for automotive cabin control systems, industrial 4–20mA sensor interfaces, USB-C power delivery monitors, and medical patient monitor front-ends requiring stable component supply with full traceability and lifecycle support.

Supply support for MMSZ5239B-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 centers across Asia and manufacturing in China, Taiwan, and the U.S.

The MMSZ52xxB series belongs to Diodes' general-purpose Zener diode product line, engineered specifically for cost-sensitive, high-volume applications demanding AEC-Q101 qualification, green material compliance, and robust SMT process compatibility.

FAQ

What is the maximum reverse voltage (V_R) that MMSZ5239B-7-F can withstand before breakdown?

The device begins controlled zener breakdown at its nominal 9.1V rating, with guaranteed operation up to 9.56V at I_ZT = 20mA. Its absolute maximum reverse voltage is not specified separately-it is designed to operate continuously only in the zener region, not as a blocking diode. For blocking applications, use a standard rectifier diode instead.

Does MMSZ5239B-7-F require a series current-limiting resistor in all applications?

Yes-this Zener diode must always be used with a series resistor to limit current to ≤20mA under worst-case input voltage and temperature conditions. Without it, excessive power dissipation will cause thermal runaway and permanent failure. The resistor value is calculated using (V_IN(MAX) − 9.1V)/I_Z(MAX), where I_Z(MAX) is derived from the 370mW power limit.

How does the temperature coefficient affect regulation accuracy over automotive temperature range?

Per Figure 6 in the datasheet, MMSZ5239B exhibits ~+0.06%/°C temperature coefficient. Over −40°C to +125°C, this introduces ±10.2mV/°C × 165°C ≈ ±1.68V total drift-so actual regulation spans ~7.4V to ~10.8V. For tighter accuracy, pair with temperature-compensated circuits or select a Zener with lower TC (e.g., MMSZ5242B at 12V has ~+0.08%/°C but better absolute stability).

Is MMSZ5239B-7-F compatible with lead-free reflow profiles per JEDEC J-STD-020?

Yes-the SOD123 package uses matte tin finish over alloy 42 leadframe and is rated for moisture sensitivity level 1, supporting standard Pb-free reflow profiles (peak 260°C, 30 sec max). Its UL 94V-0 molding compound remains stable through multiple reflow cycles without delamination or popcorning.