Microchip Technology SMAJ43E3/TR13

Overview

SMAJ43E3/TR13 from Microsemi is a unidirectional surface-mount Transient Voltage Suppressor (TVS) designed for primary and secondary lightning surge protection in DC power rails and signal lines. It features a 43 V working peak standoff voltage (V_WM), 47.8 V minimum breakdown voltage (V_BR), 76.7 V maximum clamping voltage (V_C) at 6.5 A peak pulse current, and 500 W peak pulse power rating per 10/1000 µs waveform - deployed in industrial power supplies and telecom interface circuits.

For engineers reviewing the SMAJ43E3/TR13 datasheet, SMAJ43E3/TR13 pinout, SMAJ43E3/TR13 application, or SMAJ43E3/TR13 equivalent, key selection criteria include clamping voltage margin vs. protected IC's absolute maximum rating, IEC61000-4-5 Class 3 compliance with 42 Ω source impedance, RoHS-compliant matte-tin plating, and DO-214AC package thermal performance on FR4 with 15 °C/W junction-to-lead resistance.

Technical Context

This TVS diode operates as a unidirectional avalanche clamp, triggered when reverse voltage exceeds V_BR = 47.8 V (min) at I_BR = 1 mA. Its <100 ps theoretical response time enables effective suppression of ESD per IEC61000-4-2 Level 4 (±15 kV air, ±8 kV contact) and EFT per IEC61000-4-4 (±2 kV).

It delivers 500 W peak pulse power at 25 °C with 0.01% duty cycle, derating linearly above 25 °C per the published curve. Thermal resistance is 15 °C/W junction-to-lead and 80 °C/W junction-to-ambient on FR4 (1 oz Cu), supporting reliable operation in ambient temperatures from –65 °C to +150 °C.

Key Specifications

Pinout & Package

DO-214AC (SMA) package: molded thermosetting epoxy body (UL94V-0), C-bend (modified J-bend) leads with RoHS-compliant annealed matte-tin plating; cathode indicated by band on body; weight 0.064 g; moisture sensitivity level 1 (no dry pack required).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ43E3/TR13, SMAJ43A-E3/5A offers identical electrical and mechanical specs for drop-in sourcing flexibility, while 1.5SMC43A trades slightly higher I_PP and lower V_C for reduced thermal performance - requiring layout-level thermal validation.

Availability

SMAJ43E3/TR13 is available at Aetrix Electronics and suitable for industrial power supplies, telecom line interfaces, automotive body control modules, and medical equipment DC bus protection requiring stable component supply across extended production lifecycles.

Supply support for SMAJ43E3/TR13 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 radiation-hardened components for aerospace, defense, and industrial markets.

The SMAJ series was engineered specifically for surface-mount transient suppression in harsh-environment power systems, emphasizing robust thermal performance, IEC-compliant surge handling, and long-term reliability under repeated surge stress.

FAQ

What is the clamping voltage of SMAJ43E3/TR13 and how does it protect downstream ICs?

The SMAJ43E3/TR13 has a maximum clamping voltage (V_C) of 76.7 V at 6.5 A peak pulse current (10/1000 µs waveform). This value represents the highest voltage that appears across the protected line during a surge event. By limiting transient voltage to this level, SMAJ43E3/TR13 ensures that downstream ICs rated for ≤80 V absolute maximum voltage remain within safe operating limits - preventing latch-up, gate oxide rupture, or permanent damage.

Is SMAJ43E3/TR13 bidirectional or unidirectional, and how can I identify its polarity?

SMAJ43E3/TR13 is a unidirectional TVS diode. Its polarity is identified by a cathode band marked on the DO-214AC package body - the banded end connects to the protected line (e.g., +43 V rail), while the unbanded end (anode) connects to ground. Bidirectional variants in the same family use "CA" or "C" suffixes (e.g., SMAJ43CA), which lack polarity marking.

Does SMAJ43E3/TR13 meet IEC61000-4-5 for lightning surge immunity, and at which class level?

Yes, SMAJ43E3/TR13 is qualified for IEC61000-4-5 secondary lightning surge immunity. With a 42 Ω source impedance, it supports Class 3 (1 kV test level) per the manufacturer's specification table. This makes it suitable for protection in industrial control cabinets and telecom infrastructure where moderate-level induced surges are expected.

What is the thermal resistance of SMAJ43E3/TR13, and how does it affect PCB layout?

SMAJ43E3/TR13 has a junction-to-lead thermal resistance (R_θJL) of 15 °C/W and junction-to-ambient resistance (R_θJA) of 80 °C/W when mounted on FR4 with 1 oz copper and the recommended pad layout. To maintain reliability, PCB layout must provide adequate copper area on both anode and cathode pads - especially the cathode pad - to dissipate heat during repetitive surge events and avoid thermal runaway.

What does the "TR13" suffix indicate in SMAJ43E3/TR13?

The "TR13" suffix in SMAJ43E3/TR13 specifies tape-and-reel packaging on a 13-inch reel containing 2500 units, compliant with EIA-481-1-A standards. This format is optimized for high-speed automated SMT placement equipment and ensures consistent feeding, orientation, and static-safe handling during manufacturing - critical for high-volume industrial and automotive production lines.