Microchip Technology 1N5251A/TR

Overview

1N5251A/TR 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, 29 Ω dynamic impedance at IZT, and operating from –65°C to +175°C. It provides stable voltage regulation in low-power reference and protection circuits.

For engineers reviewing the 1N5251A/TR datasheet, 1N5251A/TR pinout, 1N5251A/TR application, or 1N5251A/TR equivalent, key selection criteria include Zener voltage accuracy, thermal stability across industrial temperature ranges, low dynamic impedance for ripple suppression, and axial-leaded DO-35 compatibility with through-hole PCB assembly.

Technical Context

This device operates in reverse breakdown mode with cathode band marking polarity, requiring the banded end to be biased positive relative to the anode for regulation. Its 22 V nominal Zener voltage is specified at 5.6 mA test current (IZT), with maximum Zener impedance of 29 Ω measured at that condition.

Thermal resistance is 250 °C/W junction-to-lead (3/8" lead length) and 310 °C/W junction-to-ambient on FR4 board; derating begins above 50 °C lead temperature. Forward voltage is ≤1.5 V at 200 mA, and it exhibits a +0.087 %/°C temperature coefficient over 25–125 °C.

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.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 1N5251B/TR and MMBZ5251BS-7-F, the 1N5251A/TR offers optimal balance of cost, ruggedness, and legacy compatibility for through-hole industrial designs-especially where high-temperature operation, radiation tolerance, or ESD robustness are prioritized over tight tolerance or miniaturization.

Availability

1N5251A/TR is available at Aetrix Electronics and suitable for voltage reference, overvoltage protection, low-power bias stabilization, and calibration standard applications requiring stable component supply across extended temperature and lifecycle requirements.

Supply support for 1N5251A/TR 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 RF solutions for aerospace, defense, and industrial markets.

The 1N52xx series was designed specifically for ruggedized, high-stability Zener regulation in mission-critical systems-emphasizing wide temperature range, radiation hardness, and JEDEC-standardized interchangeability.

FAQ

What is the Zener voltage tolerance of the 1N5251A/TR?

The 1N5251A/TR has a nominal Zener voltage of 22 V with a guaranteed tolerance of ±10%, meaning its actual regulation voltage falls between 19.8 V and 24.2 V when tested at 5.6 mA. This tolerance is defined by the "A" suffix per Microsemi's documentation and applies across the full operating temperature range of –65°C to +175°C.

Does the 1N5251A/TR require heatsinking in typical applications?

No, the 1N5251A/TR does not require external heatsinking in standard applications because its 500 mW power rating is sufficient for low-current regulation tasks. At 25°C ambient, it can dissipate full power; above 50°C lead temperature, linear derating applies (250 °C/W junction-to-lead). Most designs using ≤10 mA operate well within thermal limits without added copper or airflow.

How is polarity marked on the 1N5251A/TR?

The 1N5251A/TR uses a single black band on the glass body to identify the cathode terminal. During Zener operation, the banded end must be held at a higher potential than the non-banded (anode) end. This marking is consistent across all DO-35 Zeners in the 1N52xx family and aligns with JEDEC standard polarity conventions.

Can the 1N5251A/TR replace the 1N5251B/TR in an existing design?

Yes, the 1N5251A/TR can physically and electrically replace the 1N5251B/TR in most designs, but with reduced voltage accuracy: the "A" suffix specifies ±10% tolerance versus ±5% for the "B" version. System-level validation is recommended if the original design relied on tighter regulation margins, especially under temperature extremes or aging conditions.

Is the 1N5251A/TR RoHS compliant?

Yes, the 1N5251A/TR is RoHS compliant when ordered with the "e3" suffix (e.g., 1N5251Ae3/TR). The base part number without "e3" uses traditional tin-lead plating; however, RoHS-compliant matte-tin plating is available per MIL-STD-750 Method 2026 and is standard for new production unless otherwise specified.