Microchip Technology 1N4757UR-1/TR

Overview

1N4757UR-1/TR from Microsemi is a surface-mount 1.0 W glass Zener diode with a nominal Zener voltage of 51 V, ±5% tolerance (A-suffix), 5.0 mA test current, 95 Ω dynamic impedance at I_ZT, and 5 μA maximum reverse leakage at 38.8 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 1N4757UR-1/TR datasheet, 1N4757UR-1/TR pinout, 1N4757UR-1/TR application, or 1N4757UR-1/TR equivalent, key selection criteria include Zener voltage accuracy, thermal resistance (130 °C/W on FR4), surge current rating (1500 mA), hermetic DO-213AB package suitability for high-reliability environments, and RoHS-compliant e3 variant availability.

Technical Context

This device implements a silicon planar Zener junction in a hermetically sealed glass MELF (DO-213AB) package, enabling stable breakdown behavior across wide temperature and current ranges. Its design supports regulation under steady-state DC currents up to 90 mA (IZM at TA = 50 °C) and transient surges per MIL-STD-750 pulse conditions.

The 1N4757UR-1/TR exhibits a sharp knee characteristic verified by dual-point Zener impedance measurement (IZK and IZT), with specified 18 Ω maximum knee impedance at 0.25 mA. Its forward voltage is capped at 1.2 V @ 200 mA, and it features cathode band polarity marking for unambiguous orientation during SMT placement.

Key Specifications

Pinout & Package

Package: DO-213AB glass MELF - hermetically sealed, leadless, cylindrical surface-mount package with cathode band marking; dimensions: Ø2.39–2.66 mm × 4.80–5.20 mm length; compatible with EIA-481-B 12 mm tape/reel (1500 per 7″ reel).

Key Features

Applications

Equivalent & Alternatives

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

Compared with 1N4757UR-1/TR, the 1N4757A-TR offers identical regulation performance but demands more PCB real estate and delivers inferior thermal management, while SMAJ4757A trades hermeticity and surge capability for lower cost and smaller footprint-making the 1N4757UR-1/TR optimal for high-reliability, high-temperature, or radiation-exposed deployments.

Availability

1N4757UR-1/TR is available at Aetrix Electronics and suitable for switch-mode power supplies, industrial sensor interfaces, aerospace clamping circuits, and medical overvoltage protection requiring stable component supply across extended temperature and lifecycle requirements.

Supply support for 1N4757UR-1/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, RF, and timing solutions for aerospace, defense, and industrial markets.

The 1N4757UR-1/TR belongs to Microsemi's surface-mount Zener diode family designed specifically for high-density, high-stability voltage regulation in mission-critical systems where hermetic sealing, wide temperature operation, and radiation tolerance are mandatory.

FAQ

What is the Zener voltage tolerance of the 1N4757UR-1/TR?

The 1N4757UR-1/TR has a nominal Zener voltage of 51 V with a tolerance of ±5%, indicated by the "A" suffix in its designation. This tolerance is guaranteed over the full operating temperature range (−65 °C to +175 °C) and at the specified test current of 5.0 mA. The 1N4757UR-1/TR does not support tighter tolerances like ±2% (C-suffix) or ±1% (D-suffix) - those apply only to variants explicitly marked with those suffixes.

Can the 1N4757UR-1/TR be used in lead-free reflow processes?

Yes, the 1N4757UR-1/TR is qualified for lead-free reflow with a maximum solder temperature of 260 °C for 10 seconds, per MIL-STD-750 Method 2026. Its e3 suffix confirms RoHS-compliant matte-tin plating, ensuring reliable wetting and intermetallic formation without voiding or dewetting. The 1N4757UR-1/TR's glass MELF body remains structurally intact under these conditions, unlike some plastic-packaged Zeners that may discolor or delaminate.

What is the maximum steady-state current the 1N4757UR-1/TR can regulate continuously?

The 1N4757UR-1/TR supports a maximum steady-state Zener current (I_ZM) of 90 mA at ambient temperature (T_A) = 50 °C when mounted on an FR4 PCB with 1 oz copper and the recommended pad layout. At 25 °C, derating allows up to ~100 mA, but thermal design must ensure junction temperature stays below 175 °C. Exceeding this current risks thermal runaway due to the 1N4757UR-1/TR's 130 °C/W junction-to-ambient thermal resistance.

How does the 1N4757UR-1/TR differ from the 1N4757AUR-1/TR?

The 1N4757UR-1/TR and 1N4757AUR-1/TR are identical in electrical specification, packaging (DO-213AB), and marking - the "UR" and "AUR" designations both refer to the same Microsemi surface-mount Zener series. The "A" in "AUR" denotes the ±5% voltage tolerance, not a separate variant. No functional or parametric difference exists between 1N4757UR-1/TR and 1N4757AUR-1/TR; both are valid orderable part numbers for the same device.

Is the 1N4757UR-1/TR suitable for space applications?

Yes, the 1N4757UR-1/TR is inherently radiation-hard per MicroNote 050 and qualifies for space applications when screened to MIL-PRF-19500 (e.g., JANS level with MSP prefix). Its hermetic glass MELF package eliminates moisture-induced parameter drift, and its −65 °C to +175 °C operating range covers orbital thermal extremes. The 1N4757UR-1/TR has been deployed in satellite power subsystems where long-term Zener voltage stability under total ionizing dose (TID) is critical.