Microchip Technology 1N990B

Overview

1N990B from Microsemi is a silicon 500 mW axial-lead Zener diode in DO-35 (DO-204AH) package, rated for 160 V nominal Zener voltage at 0.80 mA test current, with ±5% tolerance, +0.11 %/°C temperature coefficient, and 1700 Ω dynamic impedance at I_ZT. It regulates voltage in precision reference and overvoltage protection circuits across industrial power supplies and aerospace instrumentation.

For engineers reviewing the 1N990B datasheet, 1N990B pinout, 1N990B application, or 1N990B equivalent, key selection factors include its 160 V regulation level, low 0.25 mA maximum reverse leakage at 121.6 V, 2.2 mA maximum DC Zener current, -65°C to +175°C operating temperature range, and glass-body DO-35 mechanical robustness for high-reliability analog signal conditioning.

Technical Context

The 1N990B operates as a two-terminal voltage reference device, conducting in reverse breakdown when cathode voltage exceeds anode by ≥160 V. Its Zener mechanism dominates above ~6 V, delivering stable regulation despite variations in input current from 0.25 mA to 2.2 mA.

Thermal design requires attention: junction-to-lead thermal resistance is 250 °C/W at 3/8″ lead length, derating to 400 mW at 75 °C lead temperature. The device exhibits +0.11 %/°C voltage drift - typical for high-voltage Zeners - and maintains <5 μA leakage up to 121.6 V reverse bias.

Key Specifications

Pinout & Package

Package: DO-35 (DO-204AH), hermetically sealed axial-lead glass body, 0.2 g weight, cathode indicated by 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 regulation applications.

Compared with 1N990A and 1N990C, the 1N990B delivers the optimal balance of precision (±5%), cost, and broad industry acceptance - making it the default choice for certified industrial and aerospace designs where moderate tolerance suffices and JEDEC registration is mandatory.

Availability

1N990B is available at Aetrix Electronics and suitable for industrial power supplies, aerospace sensor interfaces, and downhole instrumentation requiring stable component supply with full traceability and long-lifecycle support.

Supply support for 1N990B 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 defense, aerospace, and industrial markets.

The 1N957B–1N992B series was engineered specifically for mission-critical voltage regulation where long-term stability, extreme temperature operation, and hermetic reliability outweigh cost-driven trade-offs.

FAQ

What is the Zener voltage tolerance for 1N990B?

The 1N990B has a nominal Zener voltage of 160 V with a ±5% tolerance, as indicated by the "B" suffix per JEDEC standard. This means the actual measured Zener voltage at 0.80 mA test current falls between 152 V and 168 V at 25°C, verified per Microsemi's REV C datasheet.

Can 1N990B be used in surface-mount designs?

No - the 1N990B is exclusively offered in the axial-lead DO-35 (DO-204AH) through-hole package. For surface-mount equivalents, Microsemi offers the MLL990B in DO-213AA (MELF) package, which shares identical electrical specifications but requires reflow-compatible layout and assembly.

What is the maximum reverse leakage current for 1N990B?

The 1N990B specifies a maximum reverse leakage current of 5 μA at 121.6 V (76% of nominal 160 V), measured at 25°C. This low leakage supports high-impedance biasing and minimizes quiescent power loss in precision analog circuits.

Does 1N990B require heatsinking in standard operation?

Heatsinking is not required for 1N990B at ambient temperatures ≤50°C and power dissipation ≤500 mW. However, thermal derating applies above 50°C lead temperature; at 75°C, maximum allowable dissipation drops to 400 mW per the power derating curve in Figure 1 of the datasheet.

Is 1N990B compliant with RoHS requirements?

The base 1N990B is not RoHS-compliant; however, the RoHS-compliant variant is designated 1N990Be3, with identical electrical and mechanical specifications except for annealed matte-tin plating instead of tin-lead. Both share the same DO-35 package and JEDEC registration.