Microchip Technology 1N4746AUR/TR

Overview

1N4746AUR/TR from Microsemi is a surface-mount 1.0 W glass-encapsulated Zener diode with a nominal Zener voltage of 18 V ±5%, 20 Ω dynamic impedance at 14 mA test current, 5 µA maximum reverse leakage at 13.7 V, and operating temperature range of −65 °C to +175 °C. It serves as a precision voltage reference or shunt regulator in power supply feedback loops, overvoltage protection circuits, and analog signal conditioning stages.

For engineers reviewing the 1N4746AUR/TR datasheet, 1N4746AUR/TR pinout, 1N4746AUR/TR application, or 1N4746AUR/TR equivalent, key selection criteria include its DO-213AB MELF glass package, hermetic sealing for high-reliability environments, tight thermal resistance (50 °C/W junction-to-end-cap), RoHS-compliant matte-tin plating, and tape-and-reel packaging (TR suffix) for automated SMT assembly.

Technical Context

This device operates in reverse-bias breakdown mode to maintain stable voltage across a wide current range (0.25 mA to 250 mA), with sharp knee characteristics verified by dual-point Zener impedance measurement per Note 2. Its glass hermetic construction ensures low parasitic capacitance and inherent radiation hardness per MicroNote 050.

The 1N4746AUR/TR is electrically equivalent to the through-hole 1N4746A but packaged in JEDEC DO-213AB outline-enabling high-density PCB layouts without sacrificing voltage regulation performance or thermal robustness. It is not a silicon planar device; its MELF geometry and glass body define its mechanical and thermal behavior.

Key Specifications

Pinout & Package

Package: DO-213AB glass MELF (Metal Electrode Leadless Face) - hermetically sealed, leadless cylindrical body with tin-lead or RoHS-compliant matte-tin plating; cathode indicated by single black band; polarity must be observed (banded end positive for Zener operation).

Key Features

Applications

Equivalent & Alternatives

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

Compared with 1N4746A and SMAJ4746A, the 1N4746AUR/TR delivers superior long-term voltage stability, radiation tolerance, and thermal response due to its hermetic glass MELF construction-making it the preferred choice for aerospace, industrial, and high-reliability power regulation where parameter drift cannot be tolerated.

Availability

1N4746AUR/TR is available at Aetrix Electronics and suitable for industrial power supplies, aerospace telemetry systems, and high-temperature sensor interfaces requiring stable component supply, consistent parametric performance, and traceable sourcing.

Supply support for 1N4746AUR/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, radiation-hardened, and precision analog components for defense, aerospace, and industrial markets.

The 1N4746AUR/TR belongs to Microsemi's legacy glass Zener diode family designed for applications demanding hermetic sealing, wide temperature operation, and parametric stability-particularly where plastic-packaged alternatives fail under thermal cycling or radiation exposure.

FAQ

What is the Zener voltage tolerance for 1N4746AUR/TR?

The 1N4746AUR/TR has a Zener voltage tolerance of ±5%, as indicated by the "A" suffix in its part number. This means its actual breakdown voltage falls within 17.1 V to 18.9 V at 14 mA test current. Tighter tolerances (±2% or ±1%) are available with "C" or "D" suffixes, but those are distinct orderable parts-not applicable to the 1N4746AUR/TR itself.

Can 1N4746AUR/TR replace 1N4746A in existing designs?

The 1N4746AUR/TR is electrically equivalent to 1N4746A but uses a DO-213AB MELF surface-mount package instead of DO-41 axial leads. Direct replacement requires PCB redesign to accommodate the cylindrical MELF footprint and reflow soldering. Mechanical mounting, thermal path, and layout rules differ significantly-so 1N4746AUR/TR is not a drop-in substitute without board revision.

What is the maximum surge current rating for 1N4746AUR/TR?

The 1N4746AUR/TR has a maximum surge current (I_S) rating of 250 mA, measured using a ½ sine-wave pulse of 1/120 second duration at 25 °C ambient. This rating applies to short-duration transients such as ESD or inductive kickback, and must be derated at elevated temperatures per the device's power derating curve in Figure 1.

Is 1N4746AUR/TR RoHS compliant?

Yes-the "e3" designation in the full part number family (e.g., 1N4746AUR-TR-e3) indicates RoHS compliance with annealed matte-tin plating. The base part number 1N4746AUR/TR is supplied with RoHS-compliant terminations unless otherwise specified; leaded versions require explicit ordering with non-RoHS suffixes.

What does the "TR" suffix mean in 1N4746AUR/TR?

The "TR" suffix denotes tape-and-reel packaging: 1N4746AUR/TR is supplied in EIA-481-B standard 12 mm carrier tape, with 1500 units per 7-inch reel. This format is required for automated SMT placement and ensures controlled static discharge, mechanical protection, and consistent feeding during high-volume manufacturing.