Diodes Incorporated MMSZ5251BS-7

Overview

MMSZ5251BS-7 from Diodes Incorporated is a surface-mount Zener diode with nominal zener voltage 22 V, ±5% tolerance (20.9–23.1 V), 5.6 mA test current, 29 Ω dynamic impedance at test current, and 200 mW power dissipation in SOD-323 package - used for precision voltage regulation and reference in low-power analog circuits, power supply feedback loops, and overvoltage protection.

For engineers reviewing the MMSZ5251BS-7 datasheet, MMSZ5251BS-7 pinout, MMSZ5251BS-7 application, or MMSZ5251BS-7 equivalent, key selection criteria include zener voltage accuracy at 5.6 mA, thermal resistance (625 °C/W), reverse leakage (<0.1 µA at 17 V), SOD-323 footprint compatibility, and RoHS-compliant lead-free plating.

Technical Context

This Zener diode operates in reverse breakdown mode to maintain stable voltage across its terminals under varying load or input conditions. It exhibits 29 Ω zener impedance at 5.6 mA and <0.1 µA reverse leakage at VR = 17 V, enabling tight regulation in low-current bias networks.

Designed for surface-mount assembly on FR-4 PCBs with recommended pad layout (AP02001), it delivers 200 mW power handling at 25°C ambient, derating linearly above 25°C per Fig. 1 - junction-to-ambient thermal resistance is 625 °C/W with standard layout.

Key Specifications

Pinout & Package

Package: SOD-323 - ultra-small plastic surface-mount case with cathode band marking; dimensions: 2.3–2.7 mm × 1.2–1.4 mm × 0.25–0.35 mm; weight ≈ 0.004 g; moisture sensitivity level 1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BZX584C22 and MMBZ5251BS, MMSZ5251BS-7 offers optimal balance of SOD-323 compactness, 200 mW rating, and 29 Ω impedance - making it preferred for space-constrained, medium-accuracy regulation where thermal management is controlled via layout.

Availability

MMSZ5251BS-7 is available at Aetrix Electronics and suitable for power supply feedback, overvoltage clamp, and voltage reference applications requiring stable component supply, consistent parametric performance, and RoHS-compliant sourcing.

Supply support for MMSZ5251BS-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 California, with design, manufacturing, and sales operations across Asia, Europe, and North America.

MMSZ5251BS-7 belongs to the MMSZ52xxBS series of general-purpose Zener diodes engineered for cost-sensitive, high-volume applications demanding reliable voltage regulation in miniature SMD packages.

FAQ

What is the maximum reverse voltage this Zener can withstand before breakdown?

The MMSZ5251BS-7 has a nominal zener voltage of 22 V with a guaranteed range of 20.9–23.1 V at 5.6 mA test current. Breakdown begins within this range; operation above 23.1 V at rated current may exceed power limits. Absolute maximum reverse voltage is not specified separately - sustained operation beyond V_Z + margin risks thermal runaway if power dissipation exceeds 200 mW.

Can this device be used in series to achieve higher reference voltages?

Yes - multiple MMSZ5251BS-7 diodes may be connected cathode-to-anode in series to sum zener voltages (e.g., two yield ~44 V). However, mismatched unit-to-unit V_Z tolerance (±5%) causes uneven voltage distribution; derating each device's power by ≥20% is required to prevent thermal imbalance and premature failure.

Is the SOD-323 package compatible with standard reflow profiles?

Yes - the SOD-323 package is qualified for lead-free reflow per J-STD-020D Level 1 moisture sensitivity. Standard IPC/JEDEC J-STD-020 profile (peak 260°C, 60–90 sec above 217°C) is appropriate. No pre-bake is required, and the matte tin plating ensures reliable solder wetting without voiding.

How does temperature affect its zener voltage stability?

The MMSZ5251BS-7 has a positive temperature coefficient (~0.07%/°C typical for 22 V Zeners), meaning V_Z increases ~15 mV/°C near 25°C. Over –65°C to +150°C operating range, total V_Z shift is approximately ±3%, which must be accounted for in precision references - compensation networks or TC-matched diodes are recommended for <0.1% stability.