Microchip Technology 1N5255A

Overview

1N5255A from Microsemi is a 28 V, ±10% tolerance, 500 mW glass axial-lead Zener diode in DO-35 (DO-204AH) package, rated for 4.5 mA test current, 600 Ω dynamic impedance at knee current, and operating across –65 °C to +175 °C - used for precision voltage reference and overvoltage protection in low-power analog circuits.

For engineers reviewing the 1N5255A datasheet, 1N5255A pinout, 1N5255A application, or 1N5255A equivalent, key selection factors include its 28 V nominal Zener voltage with ±10% tolerance (A suffix), 600 Ω Zener impedance at IZK = 0.25 mA, thermal resistance of 250 °C/W junction-to-lead, and compatibility with manual or wave soldering at 260 °C for 10 s.

Technical Context

This discrete Zener diode operates in reverse breakdown to maintain stable voltage regulation across a broad current range (0.25 mA to 20 mA), with minimal capacitance (<2.5 pF typical at 0 V) and inherent radiation hardness per MicroNote 050. Its DO-35 glass package provides hermetic sealing and ESD insensitivity per MIL-STD-750 Method 1020.

The device exhibits a positive temperature coefficient of +0.091 %/°C (25 °C to 125 °C, IZT = 4.5 mA), enabling predictable drift behavior in temperature-varying environments. It is not intended for surge suppression but for steady-state voltage clamping and reference generation in linear power supplies and sensor bias networks.

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 color band; weight 0.2 g; lead length ≥10 mm for thermal rating compliance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 1N5255B and MMBZ5255B, the 1N5255A delivers the lowest-cost solution for non-critical 28 V clamping where ±10% tolerance is acceptable and through-hole assembly is preferred; it uniquely supports higher ambient temperatures (up to +175 °C) and offers superior thermal resistance performance in leaded mounting configurations.

Availability

1N5255A is available at Aetrix Electronics and suitable for industrial sensor biasing, linear power supply reference, automotive ECU voltage monitoring, and test equipment calibration reference requiring stable component supply and long-lifecycle support.

Supply support for 1N5255A 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, RF, and radiation-hardened components for aerospace, defense, and industrial markets.

The 1N52xxA/B Zener series was designed for ruggedized voltage regulation in mission-critical systems-emphasizing wide temperature operation, hermetic packaging, and guaranteed parametric limits per JEDEC standards.

FAQ

What is the nominal Zener voltage and tolerance of the 1N5255A?

The 1N5255A has a nominal Zener voltage of 28 V with a ±10% tolerance (A suffix), meaning its actual breakdown voltage falls between 25.2 V and 30.8 V at 4.5 mA test current and 25 °C. This tolerance is guaranteed per JEDEC specification and applies across the full operating temperature range.

What package type does the 1N5255A use, and how is polarity marked?

The 1N5255A uses the DO-35 (DO-204AH) glass axial-leaded package. Polarity is marked by a single color band on the cathode end; the banded end must be held positive relative to the unbanded (anode) end during Zener operation. The package is hermetically sealed and RoHS-compliant when ordered with "e3" suffix.

What is the maximum power dissipation and thermal resistance of the 1N5255A?

The 1N5255A is rated for 500 mW power dissipation at 25 °C, with thermal resistance of 250 °C/W junction-to-lead (measured at 10 mm lead length). When mounted on FR4 with specified copper pads, junction-to-ambient thermal resistance is 310 °C/W, and power derates linearly above 25 °C per Figure 1 in the datasheet.

Does the 1N5255A require external ESD protection during PCB assembly?

No-the 1N5255A is nonsensitive to ESD per MIL-STD-750 Method 1020 and does not require external ESD protection during handling or soldering. Its glass package and internal construction provide inherent immunity, simplifying manufacturing flow and reducing BOM cost.

How does the temperature coefficient of the 1N5255A affect its regulation accuracy?

The 1N5255A has a temperature coefficient of +0.091 %/°C, meaning its Zener voltage increases by approximately 25.5 mV per 1 °C rise from 25 °C to 125 °C. This predictable positive drift enables compensation in temperature-critical designs and confirms suitability for high-temperature environments up to +175 °C.