Diodes Incorporated MMSZ5238B-7

Overview

MMSZ5238B-7 from Diodes Incorporated is a 500mW surface-mount Zener diode with a nominal zener voltage of 8.7V (±5% tolerance), 20mA test current, and 8Ω dynamic impedance at 1kHz. It features SOD123 package, cathode band polarity, and AEC-Q101 qualification for automotive-grade reliability in voltage regulation and reference applications.

For engineers reviewing the MMSZ5238B-7 datasheet, MMSZ5238B-7 pinout, MMSZ5238B-7 application, or MMSZ5238B-7 equivalent, this device serves as a precision low-power voltage clamp in power supply feedback loops, overvoltage protection circuits, and analog reference generation where stable 8.7V regulation under 20mA is required.

Technical Context

This Zener diode operates in reverse breakdown mode to maintain a stable 8.7V reference across its terminals when biased above its knee voltage. Its 8Ω zener impedance at 20mA ensures minimal voltage deviation under load variation, while its 338°C/W junction-to-ambient thermal resistance defines derating behavior on FR-4 PCBs.

The device exhibits a temperature coefficient near +0.06%/°C (per Figure 6), indicating slight positive drift with rising temperature - a key consideration in precision analog designs. Its 3.0µA maximum reverse leakage at 6.5V supports low-quiescent-current operation in battery-powered sensing nodes.

Key Specifications

Pinout & Package

SOD123 is a two-terminal surface-mount package with cathode marked by a visible band. Terminals are non-polarized in function but require correct orientation: anode connects to lower potential, cathode to higher potential during reverse-bias operation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BZX584C8V2 and 1N4737A, MMSZ5238B-7 uniquely balances 8.7V regulation, low 8Ω impedance, SOD123 SMT compatibility, and AEC-Q101 qualification - making it optimal for volume automotive and industrial surface-mount applications demanding both precision and reliability.

Availability

MMSZ5238B-7 is available at Aetrix Electronics and suitable for automotive engine control units, industrial sensor interfaces, and consumer power adapter feedback circuits requiring stable component supply with full traceability and lifecycle management.

Supply support for MMSZ5238B-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 and manufacturing operations across Asia and the Americas.

The MMSZ52xxB series belongs to Diodes' general-purpose Zener diode product line, engineered specifically for cost-sensitive, high-volume voltage regulation and clamping in automotive, industrial, and consumer electronics.

FAQ

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

The MMSZ5238B-7 begins controlled reverse breakdown at its nominal zener voltage of 8.7V, with guaranteed regulation starting at 8.27V (min) and ending at 9.14V (max) under 20mA test current. Applying voltage below 6.5V results in ≤3.0µA leakage; exceeding 9.14V risks thermal runaway if power dissipation exceeds 370mW on standard PCB layout.

Is MMSZ5238B-7 suitable for use in high-frequency noise suppression?

No - this device is not optimized for high-frequency bypassing. Its typical capacitance is ~15pF at 0V (inferred from Figure 4), and its 8Ω impedance applies only at 1kHz. For RF decoupling or EMI filtering, dedicated TVS diodes or multilayer ceramic capacitors are recommended instead.

How does the SOD123 package affect thermal performance compared to larger packages?

The SOD123 package delivers 338°C/W junction-to-ambient thermal resistance on FR-4 with 1-inch copper pad, meaning a 370mW dissipation causes ~125°C junction rise above ambient. Larger packages like DO-41 offer lower R_θJA, but SOD123's compact size enables dense layouts while maintaining AEC-Q101 reliability through optimized leadframe plating and molding compound.

Can MMSZ5238B-7 replace MMSZ5237B or MMSZ5239B in existing designs?

Yes, with design validation. MMSZ5237B (8.2V) and MMSZ5239B (9.1V) differ by ±0.4–0.5V nominal voltage and exhibit different temperature coefficients. Swapping requires checking whether the new voltage remains within system tolerance bands and whether the 8Ω vs. 10Ω (MMSZ5239B) impedance shift affects loop stability in feedback applications.