Microchip Technology 1N5279B

Overview

1N5279B from Microsemi is a 500 mW, 180 V ±5% glass axial-lead Zener diode in DO-35 (DO-204AH) package, rated for -65°C to +175°C operation, with 0.68 mA test current, 2200 Ω dynamic impedance at 0.25 mA, and +0.110 %/°C temperature coefficient - used for precision voltage reference and overvoltage clamping in industrial power supplies.

For engineers reviewing the 1N5279B datasheet, 1N5279B pinout, 1N5279B application, or 1N5279B equivalent, key selection criteria include its 180 V nominal Zener voltage, ±5% tolerance (B suffix), 500 mW power rating at 25°C, DO-35 mechanical form factor, and stable high-voltage regulation across wide temperature extremes.

Technical Context

This device operates as a two-terminal voltage reference diode, conducting in reverse breakdown at precisely 180 V when biased above its knee current (IZK = 0.25 mA), with guaranteed limits on VZ, IR, VF, ZZT, ZZK, and αVZ per JEDEC registration. Its glass DO-35 package provides hermetic sealing and radiation hardness.

It delivers stable regulation under steady-state DC conditions with minimal capacitance (<1.5 pF typical per Figure 2), low ESD sensitivity (MIL-STD-750 Method 1020), and thermal resistance of 250 °C/W junction-to-lead at 10 mm lead length - enabling reliable use in high-reliability analog monitoring circuits.

Key Specifications

Pinout & Package

DO-35 (DO-204AH) glass axial-leaded package: hermetically sealed, tin-lead or RoHS-compliant matte-tin plating, cathode indicated by band; designed for through-hole mounting with 3/8″ (10 mm) minimum lead length from body for thermal management.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 1N5279C and 1N5279D, the 1N5279B offers optimal cost-performance balance for industrial controls where ±9 V tolerance is acceptable, while retaining full JEDEC registration and radiation hardness not found in commercial-grade alternatives.

Availability

1N5279B is available at Aetrix Electronics and suitable for industrial power supplies, aerospace voltage monitors, downhole sensor biasing, and military test equipment calibration requiring stable component supply across extended temperature and radiation environments.

Supply support for 1N5279B 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 and mixed-signal components for aerospace, defense, and industrial markets.

The 1N52xxB series was engineered for mission-critical voltage regulation where long-term stability, extreme temperature resilience, and radiation tolerance are mandatory - not general-purpose replacement.

FAQ

What is the Zener voltage tolerance of the 1N5279B?

The 1N5279B has a nominal Zener voltage of 180 V with a guaranteed tolerance of ±5%, as designated by the "B" suffix per JEDEC specification. This means the actual measured VZ at IZT = 0.68 mA falls between 171 V and 189 V at 25°C. The tolerance is fully specified and tested - not derived from statistical sampling.

Does the 1N5279B require heatsinking in standard PCB layouts?

No, the 1N5279B does not require external heatsinking when operated at ≤500 mW and mounted with ≥10 mm lead length from the DO-35 glass body. Its thermal resistance is 250 °C/W junction-to-lead under those conditions. On FR4 with 4 mm² copper pads, derating begins above 25°C ambient - full power is only sustainable below 50°C lead temperature.

Can the 1N5279B be used in surface-mount designs?

No - the 1N5279B is exclusively a through-hole DO-35 axial-leaded device. Surface-mount equivalents exist in the MLL52xxB series (e.g., MLL5279B in DO-213AA MELF), but they are distinct orderable parts with different thermal and mechanical behavior; direct substitution requires layout redesign and requalification.

What is the maximum reverse leakage current for the 1N5279B?

The 1N5279B specifies a maximum reverse current (IR) of 10 μA at VR = 144 V (80% of nominal 180 V). This value is guaranteed per JEDEC test conditions and reflects leakage performance prior to reaching the sharp Zener knee - critical for low-power standby circuits where quiescent current must remain predictable.

Is the 1N5279B compliant with RoHS requirements?

Yes - RoHS-compliant versions of the 1N5279B are available with the "e3" suffix (e.g., 1N5279Be3), featuring annealed matte-tin plating per MIL-STD-750 Method 2026. Standard 1N5279B uses tin-lead plating; the e3 variant replaces lead with compliant finish while maintaining identical electrical and thermal specifications.