Microchip Technology 1N5643A

Overview

1N5643A from Microchip Technology is a unidirectional transient voltage suppressor (TVS) diode in a hermetically sealed DO-13 metal package, designed for high-reliability surge protection in aerospace and industrial systems. It features a 21.8 V rated standoff voltage (VWM), 25.7 V minimum breakdown voltage (V(BR)), 37.5 V maximum clamping voltage (VC) at 40 A peak pulse current, and 1500 W peak pulse power rating per 10/1000 µs waveform - commonly deployed in avionics power rail protection against secondary lightning surges with 12 Ω source impedance (IEC61000-4-5 Class 3).

For engineers reviewing the 1N5643A datasheet, 1N5643A pinout, 1N5643A application, or 1N5643A equivalent, key selection criteria include its unidirectional polarity, DO-13 mechanical robustness, sub-100 ps response time, radiation-hardened construction per MicroNote 050, and compliance with MIL-PRF-19500/500 for JANTXV-grade variants.

Technical Context

The 1N5643A operates as a silicon avalanche diode optimized for fast clamping of transient overvoltages on DC power lines and signal paths. Its unidirectional configuration ensures cathode-to-case polarity alignment, enabling direct mounting to chassis ground for low-inductance surge shunting. The device exhibits a positive temperature coefficient of breakdown voltage (0.096 %/°C), supporting stable performance across –55°C to +175°C operating range.

It delivers 1500 W non-repetitive peak pulse power under standardized 10/1000 µs waveform conditions at 25°C lead temperature, with thermal resistance of 50°C/W junction-to-lead (0.375″ from body). Standby leakage remains ≤5 µA at 21.8 V VWM, ensuring minimal system loading during normal operation.

Key Specifications

Pinout & Package

1N5643A uses the DO-13 (DO-202AA) axial-leaded, hermetically sealed metal-glass package. Cathode is electrically connected to the case and marked with a diode symbol on the body. Leads are tin-lead plated per MIL-STD-750 Method 2026.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar unidirectional TVS diode applications.

Compared with 1N5643, the 1N5643A offers tighter parametric control and military qualification; compared with SMBJ22A, it provides higher surge capacity, hermetic reliability, and radiation tolerance - making 1N5643A the sole choice for mission-critical airborne and defense platforms.

Availability

1N5643A is available at Aetrix Electronics and suitable for aerospace power distribution, industrial motor drive controls, avionics sensor interfaces, and railway signaling systems requiring stable component supply across extended product lifecycles.

Supply support for 1N5643A 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 (formerly Microsemi) is a U.S.-based semiconductor company specializing in high-reliability analog, mixed-signal, and radiation-hardened components for aerospace, defense, and industrial markets.

The 1N5643A belongs to Microchip's legacy JAN/JANTXV TVS diode family, engineered specifically for ruggedized transient suppression in safety-critical systems where hermetic packaging, military qualification, and extreme temperature operation are mandatory.

FAQ

What is the clamping voltage of the 1N5643A under standard IEC61000-4-5 test conditions?

The 1N5643A has a maximum clamping voltage (VC) of 37.5 V when subjected to a 10/1000 µs surge waveform at 40 A peak pulse current. This value is measured per JEDEC standards and defines the upper voltage limit imposed on protected circuitry during a Class 3 secondary lightning event with 12 Ω source impedance. The 1N5643A maintains this clamping performance across its full operating temperature range.

Is the 1N5643A suitable for ESD protection per IEC61000-4-2?

Yes, the 1N5643A is explicitly validated for ESD protection per IEC61000-4-2 due to its sub-100 ps response time and low leakage (<5 µA at 21.8 V). Its fast avalanche action clamps electrostatic discharges before they propagate into sensitive analog front-ends or digital logic. The 1N5643A is routinely deployed in avionics sensor interfaces where Level 4 (15 kV air, 8 kV contact) immunity is required.

Does the 1N5643A have military qualification, and what does the "A" suffix signify?

The "A" suffix in 1N5643A denotes tighter parametric tolerances and eligibility for MIL-PRF-19500/500 qualification when ordered with JAN, JANTX, or JANTXV prefixes (e.g., JANTXV1N5643A). These versions undergo rigorous screening including temperature cycling, burn-in, and lot acceptance testing. The base 1N5643A meets commercial specifications but can be upgraded to JANTXV grade for defense and aerospace programs requiring full military traceability.

How is the cathode terminal identified on the 1N5643A DO-13 package?

The cathode of the 1N5643A is permanently connected to the metal case and marked with a molded diode symbol on the glass body near Lead 1. Per DO-13 mechanical drawings, Lead 1 (cathode) must be soldered to chassis ground or low-impedance return to ensure optimal clamping performance. This configuration minimizes parasitic inductance in the surge current path and is essential for achieving the specified 37.5 V clamping voltage.

What is the thermal resistance and derating behavior of the 1N5643A?

The 1N5643A has a junction-to-lead thermal resistance of 50°C/W when measured at 0.375″ (10 mm) from the case body. Its steady-state power dissipation is rated at 1 W up to +125°C lead temperature, with linear derating to zero at +175°C. For pulsed operation, the 1500 W peak rating applies only at TL = 25°C and requires ≤0.01% duty cycle. The 1N5643A's metal package enables direct thermal coupling to heatsinks or chassis for sustained surge duty cycles.