Microchip Technology 1N4678

Overview

1N4678 from Microsemi is a 0.5 W, 1.8 V ±5% glass axial-leaded Zener diode in DO-7 (DO-204AA) package, rated for operation from –65 °C to +175 °C, with 50 µA test current, 0.70 V max voltage regulation (10–100 µA), and 7.5 µA max reverse leakage at 1.0 V. It serves as a precision low-voltage reference in analog power supply feedback paths and sensor bias networks.

For engineers reviewing the 1N4678 datasheet, 1N4678 pinout, 1N4678 application, or 1N4678 equivalent, key selection criteria include its 1.8 V nominal Zener voltage, tight thermal stability over military-grade temperature range, low leakage at sub-1 V reverse bias, DO-7 mechanical robustness, and compatibility with MIL-PRF-19500 screening options when prefixed with MQ/MX/MV/MSP.

Technical Context

The 1N4678 operates as a two-terminal voltage reference device relying on controlled avalanche and Zener breakdown mechanisms. Its 1.8 V nominal voltage places it in the low-voltage Zener region where temperature coefficient is negative and highly sensitive to doping profile and junction geometry.

It is characterized at 50 µA test current with guaranteed regulation ΔV_Z ≤ 0.70 V between 10 µA and 100 µA, and exhibits 7.5 µA maximum reverse leakage at 1.0 V - critical for ultra-low-power biasing in battery-operated instrumentation front-ends.

Key Specifications

Pinout & Package

DO-7 (DO-204AA) is a hermetically sealed glass axial-leaded package with tin-lead plated leads. Cathode is marked by a band; device operates with banded end positive relative to anode during Zener conduction.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 1N4678, 1N4728A provides higher voltage and power but lacks military screening options and extreme temperature capability; BZX55C1V8 matches voltage and tolerance but trades DO-7 hermetic reliability for compactness and commercial-grade qualification.

Availability

1N4678 is available at Aetrix Electronics and suitable for aerospace power conditioning, downhole instrumentation, and automotive ECU sensor biasing requiring stable component supply across extended temperature and lifecycle demands.

Supply support for 1N4678 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 1N4678 belongs to Microsemi's legacy DO-7 Zener series designed explicitly for military, aerospace, and industrial applications demanding guaranteed performance from –65 °C to +175 °C with hermetic packaging and MIL-PRF-19500 qualification pathways.

FAQ

What is the nominal Zener voltage and tolerance of the 1N4678?

The 1N4678 has a nominal Zener voltage of 1.8 V with a standard tolerance of ±5%. Tighter tolerances of ±2% and ±1% are available with C and D suffixes respectively, though the base 1N4678 part carries no suffix and defaults to ±5%. This voltage is specified at 50 µA test current and remains stable across its full operating temperature range.

Does the 1N4678 support military-grade screening?

Yes, the 1N4678 supports MIL-PRF-19500 screening when ordered with appropriate prefixes: MQ (JAN), MX (JANTX), MV (JANTXV), or MSP (JANS). These variants undergo additional environmental stress testing including temperature cycling, hermeticity verification, and radiation exposure per Microsemi's qualification protocols - making the 1N4678 suitable for Class H and K space applications when configured accordingly.

What is the maximum reverse leakage current for the 1N4678, and at what voltage is it measured?

The 1N4678 has a maximum reverse leakage current of 7.5 µA, measured at a reverse voltage of 1.0 V. This parameter is critical for low-power biasing applications where even nanoamp-level leakage could introduce significant error - such as in high-impedance sensor interfaces or battery-powered calibration references.

Can the 1N4678 be used in surface-mount designs?

No, the standard 1N4678 is a through-hole DO-7 axial-leaded device. However, Microsemi offers surface-mount equivalents under the 1N4678UR designation in DO-213AA package. The UR variant maintains identical electrical specifications but requires reflow-compatible layout and thermal pad design - users must select either 1N4678 (through-hole) or 1N4678UR (SMT) based on assembly method.

What is the thermal resistance and power derating behavior of the 1N4678?

The 1N4678 has a thermal resistance of 300 °C/W junction-to-lead (at 3/8″ lead length) and 360 °C/W junction-to-ambient on FR4 board. Its steady-state power dissipation is 500 mW at lead temperature <25 °C, derating linearly to zero at 175 °C - enabling reliable operation in high-temperature enclosures without forced cooling when mounted with adequate lead length.