Microchip Technology 1N990A

Overview

1N990A from Microsemi is a silicon 500 mW axial-leaded Zener diode in DO-35 (DO-204AH) package, rated for 160 V nominal Zener voltage with ±10% tolerance (A suffix), 0.80 mA Zener test current, 1700 Ω dynamic impedance at I_ZT, and maximum 2.2 mA DC Zener current. It operates across –65°C to +175°C and serves as a precision voltage reference or overvoltage clamp in power supply feedback loops.

For engineers reviewing the 1N990A datasheet, 1N990A pinout, 1N990A application, or 1N990A equivalent, key selection criteria include its 160 V regulation level, ±10% tolerance, DO-35 glass-body construction, thermal resistance of 310°C/W on FR4, and compatibility with lead-free reflow (e3 suffix option).

Technical Context

The 1N990A functions as a two-terminal reverse-biased voltage regulator, maintaining stable 160 V across its cathode–anode terminals when reverse current exceeds the knee region. Its Zener impedance of 1700 Ω at 0.80 mA reflects moderate regulation sharpness, suitable for non-critical biasing and coarse voltage clamping.

Designed for high-temperature operation up to +175°C, it features hermetically sealed glass packaging, tin-lead or RoHS-compliant matte-tin plating, and polarity indicated by a cathode band. It exhibits a +0.11%/°C temperature coefficient and ≤5 μA reverse leakage at 121.6 V.

Key Specifications

Pinout & Package

Package: DO-35 (DO-204AH), hermetically sealed axial-leaded glass body, 0.2 g weight, cathode identified by colored band. Terminals are solderable 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 regulation applications.

Compared with 1N990A, the 1N990B delivers tighter voltage control without altering thermal or mechanical design, while MMBZ5265B trades power capability and impedance for SMT manufacturability-neither is pin-compatible, and both require validation of thermal performance and surge handling in the target application.

Availability

1N990A is available at Aetrix Electronics and suitable for industrial power supplies, high-temperature sensor interfaces, and legacy equipment repair requiring stable component supply and long-term obsolescence management.

Supply support for 1N990A 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 and mixed-signal components for aerospace, defense, and industrial markets.

The 1N990A belongs to Microsemi's legacy JEDEC-registered 1N957B–1N992B Zener series, engineered for ruggedized voltage regulation in extreme environments including extended temperature ranges and high-radiation settings.

FAQ

What is the Zener voltage tolerance of the 1N990A?

The 1N990A has a nominal Zener voltage of 160 V with a ±10% tolerance, as designated by the "A" suffix per Microsemi's documentation. This means its actual regulation voltage falls between 144 V and 176 V at 25°C under specified test conditions (0.80 mA I_ZT). Tighter tolerances like ±5% (1N990B) or ±2% (1N990C) are available with different suffixes.

Can the 1N990A be used in surface-mount designs?

No, the 1N990A is exclusively packaged in the axial-leaded DO-35 (DO-204AH) glass case and is not a surface-mount device. For SMT equivalents, consider Microsemi's MLL990B in DO-213AA (MELF) or third-party SOT-23 options like MMBZ5265B-but note these differ in power rating, impedance, and thermal behavior. The 1N990A requires through-hole mounting.

What is the maximum steady-state power dissipation for the 1N990A?

The 1N990A is rated for 500 mW maximum steady-state power at lead temperature <50°C (measured 3/8″ from body), but its usable dissipation drops to 400 mW at 75°C lead temperature and further derates per Figure 1 in the datasheet. On FR4 with 4 mm² copper pads, its thermal resistance is 310°C/W, limiting practical continuous power to ~160 mW at +85°C ambient without heatsinking.

Does the 1N990A meet RoHS requirements?

Yes-the base 1N990A is not RoHS-compliant, but Microsemi offers the RoHS-compliant version as 1N990Ae3, where the "e3" suffix denotes annealed matte-tin plating compliant with EU RoHS Directive 2011/65/EU. Both versions share identical electrical specifications and DO-35 packaging; only the plating differs.

How does temperature affect the Zener voltage of the 1N990A?

The 1N990A has a positive temperature coefficient of +0.11 %/°C, meaning its Zener voltage increases by approximately 0.176 V per 1°C rise in junction temperature. At 160 V nominal, this results in ~17.6 V increase over a 100°C temperature span. Designers must account for this drift in high-accuracy references or use compensation networks where needed.