Microchip Technology 1N5644A

Overview

1N5644A from Microchip (formerly Microsemi) is a unidirectional transient voltage suppressor (TVS) diode in a hermetically sealed DO-13 metal package, designed for high-reliability surge protection in aerospace, avionics, and industrial systems. It features a 24.3 V minimum breakdown voltage (V_BR), 25.6 V rated standoff voltage (V_WM), 41.4 V maximum clamping voltage (V_C) at 36 A peak pulse current, and 1500 W peak pulse power rating per 10/1000 µs waveform.

For engineers reviewing the 1N5644A datasheet, 1N5644A pinout, 1N5644A application, or 1N5644A equivalent, this device is selected for secondary lightning protection (IEC 61000-4-5 Class 4 with 42 Ω source), ESD/EFT immunity (IEC 61000-4-2/-4), and fast-clamp (<100 ps) protection of DC power rails and signal lines in harsh electromagnetic environments.

Technical Context

The 1N5644A operates as a unidirectional avalanche diode, entering controlled breakdown above its 25.6 V standoff voltage to clamp transients while maintaining low leakage (<5 µA at V_WM). Its DO-13 metal-glass package provides hermetic sealing and radiation hardness per MicroNote 050, supporting operation from –55 °C to +175 °C.

It delivers 1500 W peak pulse power under 10/1000 µs surge conditions with <100 ps response time, enabling protection against inductive switching spikes, induced RF, and secondary lightning surges. Thermal resistance is 50 °C/W junction-to-lead (0.375″ from body), confirming suitability for high-power transient dissipation without PCB heatsinking.

Key Specifications

Pinout & Package

DO-13 (DO-202AA) hermetically sealed metal-glass package with axial leads. Cathode terminal is electrically connected to the metal case and marked by a diode symbol on the body.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar transient suppression applications.

Compared with 1N5644, the 1N5644A adds military screening and radiation hardness without altering electrical performance; compared with SMCJ26A, it trades surface-mount convenience for hermetic reliability and extreme-temperature capability essential in avionics.

Availability

1N5644A is available at Aetrix Electronics and suitable for aerospace power distribution, avionics sensor interface, industrial motor control feedback, and railway signaling interface requiring stable component supply, long-term obsolescence management, and traceable sourcing.

Supply support for 1N5644A 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

Microchip Technology acquired Microsemi in 2018 and maintains its high-reliability analog and discrete product portfolio, including radiation-hardened and military-qualified components for aerospace, defense, and industrial markets.

The 1N5644A belongs to Microchip's legacy TVS diode family originally developed by Microsemi for mission-critical surge protection; it targets applications demanding hermetic packaging, wide temperature operation, and compliance with MIL-PRF-19500/500.

FAQ

What is the standoff voltage (V_WM) of the 1N5644A and why does it matter?

The 1N5644A has a rated standoff voltage (V_WM) of 25.6 V, meaning it remains nonconductive below this reverse voltage. This value must exceed the maximum continuous operating voltage of the protected circuit-such as a 24 V DC rail-to prevent leakage or premature conduction. Selecting a 1N5644A for a 28 V system would risk sustained conduction and thermal failure, making V_WM a critical first-pass selection parameter for the 1N5644A.

How does the 1N5644A achieve sub-100 ps response time, and what design impact does that have?

The 1N5644A achieves <100 ps response via low-junction-capacitance avalanche structure and minimal package parasitics inherent to its DO-13 metal-glass construction. This enables clamping before ESD pulses (per IEC 61000-4-2) fully couple into sensitive nodes. In practice, this means the 1N5644A can protect FPGA I/O banks or precision ADC references without requiring additional RC filtering or layout compromises-directly improving system-level ESD pass rates in final compliance testing for the 1N5644A.

Is the 1N5644A suitable for bidirectional transient protection?

No-the 1N5644A is strictly unidirectional and conducts only in reverse bias. It cannot suppress positive-going transients on AC-coupled or bipolar signal lines. For bidirectional protection in the same DO-13 footprint, Microchip specifies the separate 1N6036–1N6072A series. Using the 1N5644A in place of a bidirectional TVS would leave the circuit vulnerable to forward-polarity surges, so correct polarity orientation and application context are essential for reliable deployment of the 1N5644A.

What does "hermetically sealed DO-13" mean for the 1N5644A's field reliability?

Hermetic sealing in the 1N5644A's DO-13 package eliminates internal moisture and gas migration, preventing corrosion, parameter drift, and latent failures under thermal cycling or high humidity. This is validated per MIL-STD-750 test methods and directly supports the 1N5644A's –55 °C to +175 °C operating range and 10+ year service life in sealed avionics enclosures-making it unsuitable for replacement with plastic-packaged equivalents like SMAJ26A in mission-critical deployments of the 1N5644A.

Can the 1N5644A be used for primary lightning protection per IEC 61000-4-5?

No-the 1N5644A is specified for secondary lightning protection only (e.g., Class 4 with 42 Ω source impedance per IEC 61000-4-5), delivering up to 4 kV clamping. Primary lightning events involve far higher energy (e.g., 10/350 µs waveforms, >10 kA), requiring coordinated protection stages with gas discharge tubes or high-energy MOVs upstream. The 1N5644A serves as the final-clamp device in such architectures, and using it alone for primary exposure would result in catastrophic failure of the 1N5644A.