Microchip Technology 1N985B

Overview

1N985B from Microsemi is a silicon 500 mW axial-lead Zener diode in DO-35 (DO-204AH) package, rated for 100 V nominal Zener voltage with ±5% tolerance (B suffix), 1.3 V maximum forward voltage at 200 mA, and +0.11 %/°C temperature coefficient. It operates across –65 °C to +175 °C and is used for precision voltage regulation in power supply reference circuits.

For engineers reviewing the 1N985B datasheet, 1N985B pinout, 1N985B application, or 1N985B equivalent, this part serves as a stable, JEDEC-registered, glass-encapsulated Zener regulator with verified thermal resistance (310 °C/W on FR4), low reverse leakage (≤5 μA at 76 V), and metallurgical bond option availability via "–1" suffix.

Technical Context

The 1N985B functions as a two-terminal voltage reference device operating in reverse breakdown mode, with Zener test current I_ZT = 1.3 mA and dynamic impedance Z_ZT = 3000 Ω at I_ZT. Its regulation stability relies on a sharp knee in the breakdown curve, validated per MicroNote 202 and JEDEC registration.

It exhibits a positive temperature coefficient (+0.11 %/°C), indicating increasing Zener voltage with rising junction temperature - a key design consideration for high-temperature industrial and aerospace applications where thermal drift must be modeled into reference accuracy budgets.

Key Specifications

Pinout & Package

Package: DO-35 (DO-204AH), hermetically sealed axial-lead glass body, cathode indicated by band; terminals plated with tin-lead or RoHS-compliant matte tin per MIL-STD-750 Method 2026.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 1N985B, 1N4764A offers higher power and lower impedance but sacrifices high-temperature and radiation resilience, while MMBZ5265B matches key electrical specs in SMT form but omits hermetic packaging and extended-temperature validation - making 1N985B uniquely suited for mission-critical analog references.

Availability

1N985B is available at Aetrix Electronics and suitable for industrial power supply reference, aerospace voltage monitor, military equipment bias network, and downhole sensor excitation requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for 1N985B 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 1N957B–1N992B series was engineered for demanding applications requiring JEDEC-standardized Zener regulation with extended thermal range, hermetic reliability, and proven radiation tolerance - especially in defense, aerospace, and energy infrastructure systems.

FAQ

What is the Zener test current for 1N985B?

The Zener test current (I_ZT) for 1N985B is 1.3 mA, as specified in the Electrical Characteristics table on page 2 of the Microsemi datasheet. This current is applied for 20 ±5 seconds under controlled lead temperature conditions to measure the nominal 100 V Zener voltage. Operating the 1N985B significantly below or above this current affects regulation accuracy and dynamic impedance, so design should target 1–5 mA for optimal stability.

Does 1N985B have RoHS-compliant variants?

Yes, the 1N985B is available in RoHS-compliant form with the "e3" suffix (e.g., 1N985Be3), using annealed matte-tin plating per MIL-STD-750 Method 2026. This variant maintains identical electrical and thermal specifications as the standard Sn/Pb version, including 500 mW power rating, 100 V Zener voltage, and –65 °C to +175 °C operating range, with no performance compromise.

What is the maximum reverse leakage current for 1N985B?

The maximum reverse leakage current (I_R) for 1N985B is 5 μA at 76 V (76% of nominal Zener voltage), per the Electrical Characteristics table. This value is measured at 25 °C and confirms low standby power consumption in high-impedance reference divider networks - critical for battery-backed or low-quiescent-current applications where leakage could shift regulation setpoints.

Can 1N985B be used in forward conduction mode?

Yes, the 1N985B can conduct in forward bias with ≤1.3 V maximum forward voltage at 200 mA, as stated in the Maximum Ratings table. While not optimized for rectification, this specification supports use cases such as polarity protection, ESD clamping, or dual-mode (forward/reverse) transient suppression - provided forward current remains within SOA limits and thermal dissipation is managed.

Is there a surface-mount equivalent to 1N985B?

Yes, Microsemi offers the MLL985B as the surface-mount equivalent in DO-213AA (MELF) package, with identical 100 V ±5% Zener voltage, 1.3 mA test current, and 3000 Ω impedance. The MLL985B shares the same electrical characteristics and temperature coefficient but uses a cylindrical glass MELF body instead of axial DO-35 - enabling automated placement while retaining hermetic sealing and high-temperature capability.