Microchip Technology 1N3518

Overview

1N3518 from Microsemi is a 400mW, 1.0V Zener voltage regulator diode in DO-35 glass package, rated for 10mA test current with ±5% tolerance and 7Ω maximum dynamic impedance, used for low-voltage reference and overvoltage protection in power supply feedback loops.

For engineers reviewing the 1N3518 datasheet, 1N3518 pinout, 1N3518 application, or 1N3518 equivalent, key selection criteria include its 1.0V nominal Zener voltage, tight 5% tolerance, low 7Ω impedance at 10mA, DO-35 hermetic glass package, and -65°C to +175°C operating temperature range.

Technical Context

This Zener diode operates in reverse breakdown to maintain stable 1.0V across its terminals under regulated current conditions, with thermal equilibrium measurement per Note 1 of LDS-0063 Rev. 2. Its 7Ω dynamic impedance (measured with 10% 60Hz AC superimposed on 10mA DC) ensures minimal voltage variation under load transients.

The DO-35 hermetically sealed glass case provides reliable long-term stability and moisture resistance, while the tin/lead lead finish supports standard soldering processes. Junction temperature range (-65°C to +175°C) enables use in high-reliability industrial and aerospace environments where thermal cycling is critical.

Key Specifications

Pinout & Package

Package: DO-35 hermetically sealed glass case with cathode band marking polarity. Axial leads, tin/lead finish.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 1N3518, 1N4728A serves higher-voltage applications and requires PCB redesign due to DO-41 footprint, while BZX55C1V0 offers identical 1.0V regulation in DO-35 with 12.5% higher power headroom-making it suitable for thermally constrained layouts needing extra margin.

Availability

1N3518 is available at Aetrix Electronics and suitable for low-voltage reference design, overvoltage clamp circuits, and power supply feedback networks requiring stable component supply and long-term parametric consistency.

Supply support for 1N3518 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, mixed-signal, and RF components for aerospace, defense, and industrial markets.

The 1N35xxA series was designed specifically for precision low-power Zener regulation in mission-critical systems where hermetic packaging and wide temperature stability are mandatory.

FAQ

What is the nominal Zener voltage and test current for 1N3518?

The 1N3518 has a nominal Zener voltage of 1.0 V measured at a test current (I_ZT) of 10 mA, with ±5% tolerance. This value is specified under thermal equilibrium at 25°C ambient per LDS-0063 Rev. 2. The 1N3518 maintains this regulation point with 7Ω maximum dynamic impedance, making it suitable for precision low-voltage reference applications where stability at low current is essential.

What package type does 1N3518 use and how is polarity identified?

The 1N3518 uses a DO-35 hermetically sealed glass package with axial leads and tin/lead plating. Polarity is marked by a visible cathode band on the glass body, indicating the cathode terminal. This band must be oriented toward the higher-potential node in shunt regulator configurations. The 1N3518's DO-35 form factor ensures compatibility with legacy through-hole assembly processes and high-reliability environmental sealing.

What is the maximum power dissipation and thermal operating range for 1N3518?

The 1N3518 is rated for 400 mW maximum power dissipation at 25°C ambient and supports a junction/storage temperature range of -65°C to +175°C. Derating is required above 25°C per the device's thermal resistance profile. The 1N3518's wide temperature capability allows uninterrupted operation in automotive engine compartments and industrial motor drives where ambient extremes exceed commercial-grade limits.

How does the Zener impedance of 1N3518 affect regulation performance?

The 1N3518 exhibits a maximum Zener impedance of 7 Ω at 10 mA test current, measured using 60 Hz AC superimposed on DC per Note 2 of LDS-0063 Rev. 2. This low impedance ensures minimal voltage deviation during load transients, directly improving regulation accuracy in feedback and reference circuits. In practice, the 1N3518 delivers tighter voltage stability than higher-impedance Zeners in the same family, especially under dynamic current conditions.

Can 1N3518 be used as a replacement for other 1.0V Zener diodes like BZX55C1V0?

Yes, the 1N3518 is functionally comparable to BZX55C1V0 in 1.0V regulation, DO-35 package, and ±5% tolerance, though BZX55C1V0 is rated for 500 mW versus 400 mW for the 1N3518. No PCB changes are needed for substitution, but thermal validation is recommended if operating near maximum power. The 1N3518 remains the preferred choice where Microsemi's hermetic reliability and proven field history are required.