Microchip Technology 1N5251A

Overview

1N5251A from Microsemi is a 22 V, ±10% tolerance, 500 mW glass axial-lead Zener diode in DO-35 (DO-204AH) package, rated for 5.6 mA test current and 29 Ω dynamic impedance at IZK, operating across –65°C to +175°C. It serves as a precision voltage reference or shunt regulator in low-power analog circuits, power supply feedback paths, and overvoltage protection.

For engineers reviewing the 1N5251A datasheet, 1N5251A pinout, 1N5251A application, or 1N5251A equivalent, key selection criteria include Zener voltage stability under varying temperature (αVZ = +0.087 %/°C), low reverse leakage (≤0.1 μA at 17.6 V), and thermal resistance of 250 °C/W junction-to-lead - critical for compact PCB layouts with limited heatsinking.

Technical Context

This device operates in reverse-bias breakdown mode, delivering stable 22 V regulation with a sharp knee at IZK = 0.25 mA and nominal test current IZT = 5.6 mA. Its DO-35 glass package enables hermetic sealing and inherent radiation hardness per MicroNote 050.

Thermal performance is defined by two derating profiles: 0.5 W at TL ≤ 50°C (3/8″ lead length) or 0.48 W at TA ≤ 25°C on FR4 with 4 mm² copper pads. Forward voltage is capped at 1.5 V @ 200 mA, confirming robust forward conduction capability for bidirectional clamping verification.

Key Specifications

Pinout & Package

DO-35 (DO-204AH) hermetically sealed glass axial-leaded package with cathode indicated by a single black band. Leads are tin-lead or RoHS-compliant matte-tin plated, solderable per MIL-STD-750 Method 2026. Weight: 0.2 g.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 1N5251A, the 1N4742A offers higher power margin and tighter tolerance at the cost of larger package size, while the BZX55C22 matches the DO-35 footprint and power rating but improves regulation accuracy and impedance - making it ideal for drop-in upgrades where ±5% stability is critical.

Availability

1N5251A is available at Aetrix Electronics and suitable for power supply feedback, overvoltage protection, and temperature-stable reference applications requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for 1N5251A 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

Microsemi (now part of Microchip Technology) is a U.S.-based semiconductor company specializing in high-reliability analog, mixed-signal, and radiation-hardened components for aerospace, defense, and industrial markets.

The 1N52xx series was designed as a JEDEC-standardized family of general-purpose, glass-passivated Zener diodes targeting cost-sensitive yet thermally demanding applications where hermetic reliability and wide temperature operation are essential.

FAQ

What is the Zener voltage tolerance for 1N5251A?

The 1N5251A has a nominal Zener voltage of 22 V with a guaranteed tolerance of ±10%, as indicated by the "A" suffix per Microsemi's documentation. This tolerance applies under standard test conditions (IZT = 5.6 mA, TA = 25°C) and is validated across the full operating temperature range. The 1N5251A does not carry tighter tolerance suffixes (e.g., C or D), so ±10% is its specified limit.

Can 1N5251A be used in surface-mount designs?

No - the 1N5251A is exclusively offered in the axial-leaded DO-35 (DO-204AH) glass package and is not a surface-mount device. For SMT equivalents, Microsemi lists MLL5251B in DO-213AA (MELF) package; however, that part carries a "B" suffix (±5% tolerance) and differs electrically and mechanically from the 1N5251A. Direct substitution requires board redesign.

What is the maximum reverse leakage current for 1N5251A?

The maximum reverse leakage current (IR) for 1N5251A is 0.1 μA, measured at VR = 17.6 V (80% of nominal VZ). This value is specified in the Electrical Characteristics table and holds across the full operating temperature range. It reflects minimal standby current draw, critical for battery-powered or high-impedance bias networks.

Does 1N5251A require heatsinking in typical applications?

Heatsinking is not required for 1N5251A in typical applications operating below 0.5 W at ambient temperatures ≤25°C. Its thermal resistance is 250 °C/W junction-to-lead (at 3/8″ lead length), meaning a 125°C junction rise occurs at full 0.5 W. Derating begins above 50°C lead temperature; for sustained 0.4 W operation, ensure lead length ≥10 mm and avoid enclosed enclosures without airflow.

Is 1N5251A compliant with RoHS requirements?

Yes - RoHS-compliant versions of 1N5251A are available with the "e3" suffix (e.g., 1N5251Ae3), indicating annealed matte-tin plating per J-STD-609. Standard 1N5251A may use tin-lead plating unless otherwise specified; always verify the suffix and packaging label to confirm RoHS status before use in regulated markets.