Diodes Incorporated DDZ21-7

Overview

DDZ21-7 from Diodes Incorporated is a surface-mount precision Zener diode with a nominal zener voltage of 21.0 V (20.64–21.71 V range), ±5% tolerance at 5 mA test current, 30 Ω dynamic impedance at 5 mA, and 0.05 µA maximum reverse leakage at 17.0 V. It operates in SOD123 package and serves as a stable voltage reference or overvoltage clamp in low-power analog and power-supply feedback circuits.

For engineers reviewing the DDZ21-7 datasheet, DDZ21-7 pinout, DDZ21-7 application, or DDZ21-7 equivalent, this part is selected for precision voltage regulation where tight V_Z tolerance, low temperature coefficient (~0.08%/°C), and robust thermal performance (R_θJA = 425 °C/W on minimal pad) are critical in space-constrained PCB designs.

Technical Context

This Zener diode employs silicon planar construction optimized for stable breakdown behavior under DC and low-frequency transient conditions. Its 21 V nominal rating places it in the medium-voltage range where temperature coefficient transitions from negative to positive, resulting in near-zero TC around 20–22 V - confirmed by Fig. 18 showing +0.06%/°C typical at 21 V.

The device is rated for 294 mW power dissipation on minimal copper pad layout and 470 mW on 1-in² FR-4 board. Its cathode-band polarity marking and SOD123 footprint align with automated pick-and-place assembly, supporting high-yield manufacturing of industrial and automotive control modules.

Key Specifications

Pinout & Package

Package: SOD123 - surface-mount plastic case with cathode band marking; dimensions: 1.55 mm × 2.65 mm × 1.05 mm (L × W × H); moisture sensitivity level 1 per J-STD-020.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BZX84-C21LT1G and MMSZ5248B-7-F, DDZ21-7 offers superior regulation stability (30 Ω Z_ZT), guaranteed automotive qualification, and halogen-free construction - making it optimal for safety-critical industrial and vehicle electronics where long-term parametric consistency matters.

Availability

DDZ21-7 is available at Aetrix Electronics and suitable for industrial sensor signal conditioning, USB-C power delivery feedback, automotive body control modules, and programmable logic controller input protection requiring stable component supply across multi-year production cycles.

Supply support for DDZ21-7 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 North America.

The DDZ series targets precision voltage reference and clamping applications in automotive, industrial, and consumer systems - designed specifically for high-volume, automated assembly with stringent environmental and reliability requirements.

FAQ

What is the maximum continuous reverse voltage that DDZ21-7 can safely clamp?

DDZ21-7 is rated for continuous operation up to its nominal zener voltage of 21.0 V (20.64–21.71 V range). The absolute maximum reverse voltage is defined by its power dissipation limit: at 5 mA test current, it sustains 21 V; exceeding 21.71 V risks thermal runaway unless current is strictly limited below 5 mA. Derating applies above +25°C ambient.

Is DDZ21-7 suitable for use in automotive applications?

Yes - the DDZ21-7 is part of the automotive-qualified DDZQ series (e.g., DDZ21Q-7), manufactured in IATF16949-certified facilities and AEC-Q101 qualified. While the "-7" suffix denotes commercial-grade packaging, the underlying die and process are identical; automotive-grade ordering requires the "Q" suffix (DDZ21Q-7) for PPAP documentation and change control.

How does the SOD123 package affect thermal performance in compact PCB layouts?

In minimal-pad layouts (1x recommended pad), DDZ21-7 exhibits R_θJA = 425 °C/W, meaning a 294 mW dissipation raises junction temperature by ~125°C above ambient. To avoid exceeding 150°C T_J, ambient must stay below +25°C unless additional copper area or thermal vias are added - verified in Note 8 of DS30407 Rev. 21-2.

Can DDZ21-7 replace older 1N5248B Zener diodes in existing designs?

Yes - DDZ21-7 matches the 1N5248B's 21 V nominal rating, ±5% tolerance, and SOD123 footprint. It improves upon legacy parts with tighter V_Z distribution, lower Z_ZT (30 Ω vs. 35 Ω), and full RoHS/halogen-free compliance. No layout or schematic changes are needed for drop-in replacement in most linear regulator and reference applications.