Microchip Technology 1N989A

Overview

1N989A from Microsemi is a silicon 500 mW axial-lead Zener diode with nominal Zener voltage 150 V, ±10% tolerance (A suffix), 0.85 mA Zener test current (IZT), 1500 Ω dynamic impedance (ZZT) at IZT, and +0.11 %/°C temperature coefficient - used for precision voltage reference and overvoltage protection in industrial power supplies and analog signal conditioning circuits.

For engineers reviewing the 1N989A datasheet, 1N989A pinout, 1N989A application, or 1N989A equivalent, key selection criteria include its 150 V regulation level, DO-35 glass package thermal limits (250 °C/W junction-to-lead), low reverse leakage (5 μA @ 114 V), and compatibility with through-hole PCB mounting requiring stable voltage clamping under varying temperature and load conditions.

Technical Context

The 1N989A operates as a two-terminal voltage-reference device in reverse-bias breakdown mode, delivering regulated output across a wide operating current range (IZK = 0.25 mA to IZM = 2.4 mA) and temperature span (–65 °C to +175 °C). Its Zener knee is stabilized by internal metallurgical construction, with minimal capacitance (<1.5 pF typical per Figure 3) and inherent radiation hardness per MicroNote 050.

It exhibits a positive temperature coefficient (+0.11 %/°C), meaning its Zener voltage increases linearly with junction temperature - critical for biasing stability in high-temperature environments. Thermal resistance of 250 °C/W (junction-to-lead at 10 mm lead length) defines safe power derating above TL = 50 °C, limiting steady-state dissipation to 400 mW at 75 °C lead temperature.

Key Specifications

Pinout & Package

DO-35 glass axial-leaded package: cathode indicated by color band; diode operated with banded end positive relative to unbanded end during Zener regulation. Leads are tin-lead or RoHS-compliant matte-tin plated, 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 1N989B and 1N989C, the 1N989A offers the broadest voltage tolerance at lowest unit cost while maintaining identical thermal performance, package, and reliability - making it ideal for non-critical clamping where absolute precision is secondary to robustness and BOM simplicity.

Availability

1N989A is available at Aetrix Electronics and suitable for industrial power supply regulation, overvoltage protection circuits, and high-temperature sensor biasing requiring stable component supply across extended lifecycle programs.

Supply support for 1N989A 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 radiation-hardened components for aerospace, defense, and industrial markets.

The 1N957B–1N992B series was designed specifically for ruggedized voltage regulation in mission-critical systems where long-term stability, wide temperature operation, and ESD immunity are essential - not general-purpose consumer use.

FAQ

What is the Zener voltage tolerance for 1N989A?

The 1N989A has a nominal Zener voltage of 150 V with a ±10% tolerance, as indicated by the "A" suffix per JEDEC standard. This means the actual measured V_Z at I_ZT = 0.85 mA falls between 135 V and 165 V at 25 °C. The tolerance is wider than the B (±5%) or C (±2%) variants, reflecting its intended use in non-precision clamping applications where cost and robustness are prioritized over tight regulation.

What is the maximum power dissipation for 1N989A at room temperature?

The 1N989A is rated for 500 mW steady-state power dissipation only when lead temperature (T_L) is maintained below 50 °C at 10 mm from the body. At ambient temperature (T_A) < 25 °C on FR4 board with defined copper pads, its usable power drops to 480 mW. Derating begins linearly above 50 °C TL, reaching 400 mW at 75 °C TL - the limit for calculating I_ZM = 2.4 mA.

Does 1N989A have RoHS compliance options?

Yes - RoHS-compliant versions of 1N989A are available by adding the "e3" suffix (e.g., 1N989Ae3), indicating annealed matte-tin plating per JEDEC standards. The base 1N989A uses traditional tin-lead plating. Both variants share identical electrical and thermal specifications, with RoHS compliance verified per Microsemi's published environmental documentation.

What is the reverse leakage current specification for 1N989A?

The 1N989A specifies a maximum reverse leakage current (I_R) of 5 μA when tested at 114 V - which is 76% of its nominal 150 V Zener voltage. This low leakage ensures minimal power loss in standby mode and high impedance in the non-conducting state, supporting clean voltage clamping without loading upstream circuitry.

Can 1N989A be used in high-radiation environments?

Yes - the 1N989A exhibits inherent radiation hardness as documented in Microsemi MicroNote 050. Its DO-35 glass package and silicon Zener structure enable reliable operation under total ionizing dose (TID) exposure relevant to aerospace and nuclear instrumentation applications, without requiring additional shielding or derating beyond standard thermal limits.