Microchip Technology 1N4749UR/TR

Overview

1N4749UR/TR from Microsemi is a surface-mount 1.0 W glass-encapsulated Zener diode with nominal Zener voltage 24 V, ±5% tolerance (A-suffix), 10.5 mA test current, 25 Ω dynamic impedance at I_ZT, and 5 μA maximum reverse leakage at 18.2 V. It operates from –65 °C to +175 °C and is used for precision voltage regulation in high-density power supply feedback loops.

For engineers reviewing the 1N4749UR/TR datasheet, 1N4749UR/TR pinout, 1N4749UR/TR application, or 1N4749UR/TR equivalent, key selection criteria include its DO-213AB MELF glass package, hermetic sealing, radiation hardness per MicroNote 050, low parasitic capacitance, and compatibility with automated SMT assembly under JEDEC-compliant reflow profiles.

Technical Context

This device functions as a two-terminal voltage reference diode operating in reverse breakdown. Its Zener voltage is stabilized across a broad current range (0.25 mA to 190 mA) and temperature span (–65 °C to +175 °C), with thermal resistance of 130 °C/W junction-to-ambient on FR4.

The DO-213AB glass MELF package provides hermetic sealing, ESD insensitivity, and inherent radiation hardness. Polarity is marked by a cathode band; regulation requires the banded end to be biased positive relative to the anode.

Key Specifications

Pinout & Package

DO-213AB glass MELF package: cylindrical, leadless, hermetically sealed glass body with cathode band marking; dimensions A = 2.39–2.66 mm (diameter), B = 4.80–5.20 mm (length); mounted via end-cap soldering on symmetric circular pads.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 1N4749UR/TR, 1N4749A offers identical regulation performance but lacks SMT compatibility and hermetic reliability, while SMAJ4749A sacrifices temperature range and environmental robustness for lower cost and plastic handling convenience.

Availability

1N4749UR/TR is available at Aetrix Electronics and suitable for switching power supplies, industrial sensor interfaces, aerospace avionics monitoring, and downhole instrumentation requiring stable component supply across extended temperature and radiation-exposed environments.

Supply support for 1N4749UR/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 high-temperature analog and mixed-signal components.

The 1N47xxUR/TR series was designed for mission-critical voltage regulation in aerospace, defense, oil & gas, and industrial systems where hermeticity, temperature resilience, and long-term parametric stability are mandatory.

FAQ

What is the Zener voltage tolerance of the 1N4749UR/TR?

The 1N4749UR/TR has a nominal Zener voltage of 24 V with ±5% tolerance, indicated by the "A" suffix in its full designation. This tolerance is verified at 30 °C with 10.5 mA test current and applies across its full operating temperature range from –65 °C to +175 °C. The 1N4749UR/TR achieves this specification using a tightly controlled diffusion process in its glass MELF structure.

Is the 1N4749UR/TR compatible with lead-free reflow soldering?

Yes, the 1N4749UR/TR is rated for solder exposure up to 260 °C for 10 seconds, fully compliant with IPC/JEDEC J-STD-020 lead-free reflow profiles. Its DO-213AB glass MELF package uses annealed matte-tin plating that meets MIL-STD-750 Method 2026, ensuring reliable wetting and intermetallic formation without cracking or delamination during standard SMT assembly.

How does the 1N4749UR/TR differ from the 1N4749A in practical use?

The 1N4749UR/TR and 1N4749A share identical electrical specifications including 24 V Zener voltage, ±5% tolerance, and 1.0 W power rating, but differ physically: the 1N4749UR/TR uses a surface-mount DO-213AB glass MELF package, while the 1N4749A uses an axial DO-41 package. This makes the 1N4749UR/TR suitable for high-density PCBs and automated placement, whereas the 1N4749A is limited to through-hole assembly.

What is the maximum reverse leakage current for the 1N4749UR/TR at 18.2 V?

The 1N4749UR/TR specifies a maximum reverse leakage current (I_R) of 5 μA at 18.2 V (75% of nominal V_Z). This value is measured at 30 °C and guarantees minimal standby current draw in precision reference circuits, supporting ultra-low-power designs such as battery-backed sensor nodes and energy-harvesting systems where quiescent current must remain below 10 μA.

Does the 1N4749UR/TR require any special handling for ESD sensitivity?

No, the 1N4749UR/TR is explicitly characterized as ESD-insensitive in its official documentation. As a two-terminal Zener diode with no MOS gates or fragile junctions, it withstands standard handling without ESD protection measures. Its glass MELF construction and robust PN junction eliminate the need for static-dissipative packaging or wrist straps during SMT placement or manual handling.