Microchip Technology 1N5349A/TR8

Overview

1N5349A/TR8 from Microsemi is a 12 V, ±10% tolerance, 5 W axial-leaded silicon Zener diode optimized for voltage regulation in power supply feedback loops, overvoltage protection circuits, and precision reference applications requiring stable breakdown under varying load and temperature. It delivers 100 mA maximum Zener current (IZM) at 25°C with 2.5 Ω dynamic impedance (ZZ) and operates from –65°C to +150°C.

For engineers reviewing the 1N5349A/TR8 datasheet, 1N5349A/TR8 pinout, 1N5349A/TR8 application, or 1N5349A/TR8 equivalent, key selection criteria include its 12 V nominal Zener voltage, ±10% tolerance (A suffix), 5 W power rating with thermal derating, low 2.5 Ω impedance at 100 mA test current, and RoHS-compliant matte-tin lead plating per MIL-STD-750.

Technical Context

This discrete Zener diode functions as a two-terminal voltage reference device operating in reverse-biased avalanche breakdown mode. Its regulation performance is defined by specified Zener voltage (VZ = 12 V), dynamic impedance (ZZ = 2.5 Ω), and voltage regulation (ΔVZ = 0.25 V) measured between 10% and 50% of IZM.

Thermal design relies on junction-to-lead resistance of 25 °C/W at 10 mm lead length, enabling 5 W steady-state dissipation only with adequate heat sinking; mounted on FR4 with 4 mm² copper pads, it derates to 1.47 W at 25°C ambient.

Key Specifications

Pinout & Package

Package: Axial-leaded T-18 plastic case (JEDEC DO-204AL), void-free thermosetting epoxy body (UL94V-0), cathode indicated by band. 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 regulation applications.

Compared with 1N5349B/TR8, the 1N5349A/TR8 trades tighter voltage tolerance for cost efficiency in less critical regulation roles; versus MMBZ5242B-TP, it provides 10× higher power handling and axial-leaded mechanical robustness but requires more board area and thermal design attention.

Availability

1N5349A/TR8 is available at Aetrix Electronics and suitable for switching power supplies, overvoltage protection circuits, and precision voltage reference designs requiring stable component supply with full traceability and long-term lifecycle support.

Supply support for 1N5349A/TR8 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 1N53xx series was designed as a JEDEC-standardized, high-power axial Zener family delivering robust voltage regulation for mission-critical power conditioning and protection applications across extreme temperature and surge environments.

FAQ

What is the Zener voltage tolerance for 1N5349A/TR8?

The "A" suffix in 1N5349A/TR8 specifies a ±10% Zener voltage tolerance at 100 mA test current. This means the actual breakdown voltage falls between 10.8 V and 13.2 V under standard test conditions (TL = 25°C). This tolerance is wider than the ±5% offered by the "B" variant (1N5349B/TR8), making the "A" version suitable for applications where cost sensitivity outweighs tight regulation requirements. The 1N5349A/TR8 remains fully compliant with JEDEC DO-204AL mechanical standards.

Can 1N5349A/TR8 be used in surface-mount designs?

No, the 1N5349A/TR8 is an axial-leaded T-18 package (JEDEC DO-204AL) and is not compatible with surface-mount assembly processes. For SMT equivalents, Microsemi offers the SMBJ5349A series in SMB package or the SMBG5349A in SMBG format - both rated for 5 W but requiring different footprint and reflow profiles. Substituting 1N5349A/TR8 into an SMT layout would require mechanical adaptation and is not recommended without redesign validation.

What is the maximum steady-state power dissipation for 1N5349A/TR8 on a standard FR4 PCB?

When mounted on a standard FR4 PCB with 1 oz copper, 4 mm² copper pads, and 1 mm track width (25 mm length), the 1N5349A/TR8 has a thermal resistance of 85°C/W junction-to-ambient, limiting its steady-state power dissipation to 1.47 W at 25°C ambient temperature. Exceeding this requires forced air cooling, larger copper areas, or heatsinking. At 3/8 inch (10 mm) lead length from body, it sustains full 5 W only if lead temperature (TL) is held at ≤25°C - a condition rarely met without external thermal management.

Does 1N5349A/TR8 meet RoHS requirements?

Yes, the "TR8" suffix indicates tape-and-reel packaging, and the base part 1N5349A is RoHS compliant when ordered with the "e3" suffix (e.g., 1N5349Ae3/TR8). The device uses RoHS-compliant matte-tin lead plating per MIL-STD-750 Method 2026 and void-free UL94V-0 epoxy encapsulation. Standard production lots shipped by Microsemi post-2008 comply with EU RoHS Directive 2011/65/EU, and full material declarations are available upon request for 1N5349A/TR8.

How does the voltage regulation (ΔVZ) specification impact circuit performance for 1N5349A/TR8?

The voltage regulation ΔVZ = 0.25 V for 1N5349A/TR8 quantifies the change in Zener voltage between 10% and 50% of its maximum Zener current (IZM = 100 mA), i.e., from 10 mA to 50 mA. This small ΔVZ indicates excellent line regulation - critical in feedback networks where even minor VZ drift introduces output error. In practice, this allows the 1N5349A/TR8 to maintain stable reference points across varying load currents without requiring additional compensation, directly improving power supply accuracy and sensor excitation stability.