Microchip Technology 1N985A

Overview

1N985A from Microsemi is a silicon 500 mW axial-leaded Zener diode in DO-35 (DO-204AH) package, rated for 100 V nominal Zener voltage with ±10% tolerance (A suffix), 1.3 V maximum forward voltage at 200 mA, and 3.7 mA maximum DC Zener current. It operates across –65°C to +175°C and is used for precision voltage regulation in power supply reference circuits.

For engineers reviewing the 1N985A datasheet, 1N985A pinout, 1N985A application, or 1N985A equivalent, key selection factors include its 100 V Zener voltage, ±10% tolerance, 500 mW power rating, DO-35 glass package, and temperature coefficient of +0.11 %/°C - critical for stable reference design under thermal variation.

Technical Context

The 1N985A functions as a two-terminal voltage reference device operating in reverse breakdown mode, with Zener regulation established at 100 V nominal voltage under 1.3 mA test current. Its junction-to-lead thermal resistance is 250 °C/W at 3/8″ lead length, supporting reliable operation up to 175°C ambient.

It exhibits a positive temperature coefficient of +0.11 %/°C, indicating increasing Zener voltage with rising temperature - a key consideration when used in temperature-compensated reference stacks or bias networks requiring predictable drift behavior.

Key Specifications

Pinout & Package

Package: DO-35 (DO-204AH), hermetically sealed axial-leaded glass body with cathode indicated by color band. Tin-lead or RoHS-compliant matte-tin plating, solderable 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 1N985A, the 1N985B offers improved voltage accuracy (±5% vs. ±10%) at no change in thermal or electrical envelope, while 1N985C further tightens tolerance to ±2% - making both viable alternatives when higher precision is needed without altering board layout or thermal design.

Availability

1N985A is available at Aetrix Electronics and suitable for power supply reference, overvoltage protection, voltage monitoring, and temperature-compensated bias network applications requiring stable component supply across extended temperature ranges.

Supply support for 1N985A 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-voltage analog components for aerospace, defense, and industrial markets.

The 1N957B–1N992B series, including 1N985A, was designed specifically for ruggedized voltage regulation in mission-critical systems where wide temperature operation, hermetic sealing, and ESD immunity are mandatory.

FAQ

What is the Zener voltage tolerance for 1N985A?

The 1N985A has a nominal Zener voltage of 100 V with a ±10% tolerance, as indicated by the "A" suffix per JEDEC standard. This means the actual measured Zener voltage at 1.3 mA test current falls between 90 V and 110 V at 25°C. The tolerance directly impacts reference accuracy in feedback networks and must be accounted for in worst-case circuit analysis.

What is the maximum power dissipation for 1N985A at room temperature?

The 1N985A is rated for 500 mW steady-state power dissipation at lead temperature (TL) below 50°C, measured 3/8″ from the body. At ambient temperature (TA) < 25°C on FR4 with defined copper pads, it delivers 480 mW. Derating begins above 50°C per the published power derating curve, reaching zero at 175°C junction temperature.

Is 1N985A RoHS compliant?

The base 1N985A is not RoHS compliant by default. RoHS compliance requires the "e3" suffix (e.g., 1N985Ae3), which denotes annealed matte-tin plating per Microsemi's specification. Standard 1N985A uses tin-lead (Sn/Pb) terminations unless otherwise ordered with the e3 suffix.

What does the "A" suffix mean in 1N985A?

The "A" suffix in 1N985A designates ±10% tolerance on the nominal Zener voltage, per JEDEC standard. Other suffixes include "B" for ±5%, "C" for ±2%, and "D" for ±1%. No suffix indicates ±20% tolerance. This suffix is critical for selecting the appropriate accuracy grade for each application.

Can 1N985A be used in high-temperature environments?

Yes, the 1N985A is qualified for continuous operation from –65°C to +175°C, with thermal resistance of 250 °C/W junction-to-lead. Its hermetic DO-35 glass package and radiation-hardened construction make it suitable for downhole oil/gas, aerospace, and military applications where extended temperature stability is required.