Microchip Technology SMAJ45AE3/TR13

Overview

SMAJ45AE3/TR13 from Microsemi is a unidirectional surface-mount Transient Voltage Suppressor (TVS) diode designed for primary and secondary lightning surge protection in DC power rails and signal lines. It features a 45 V reverse standoff voltage (V_WM), 50.0 V minimum breakdown voltage (V_BR), 72.7 V maximum clamping voltage (V_C) at 6.9 A peak pulse current, and 500 W peak pulse power rating per 10/1000 µs waveform - deployed in telecom power supplies, industrial I/O modules, and automotive body control units.

For engineers reviewing the SMAJ45AE3/TR13 datasheet, SMAJ45AE3/TR13 pinout, SMAJ45AE3/TR13 application, or SMAJ45AE3/TR13 equivalent, key selection criteria include clamping voltage margin vs. protected IC's absolute maximum rating, unidirectional polarity alignment with DC rail directionality, RoHS-compliant matte-tin plating compatibility with lead-free reflow, and DO-214AC package thermal performance on FR4 with 1 oz copper.

Technical Context

This TVS operates as a silicon avalanche diode that remains non-conductive below V_WM = 45 V and enters low-impedance clamping mode within <100 ps when transient voltage exceeds V_BR = 50.0 V (tested at I_BR = 1 mA). Its unidirectional configuration provides forward conduction capability (40 A surge, 3.5 V max forward voltage) while blocking reverse leakage (<1 µA at V_WM).

The device meets IEC61000-4-2 (±15 kV contact ESD), IEC61000-4-4 (±2 kV EFT), and IEC61000-4-5 Class 3 secondary lightning (42 Ω source, 1 kV test level) when used with appropriate series impedance. Thermal resistance is 15 °C/W junction-to-lead and 80 °C/W junction-to-ambient on standard FR4 layout.

Key Specifications

Pinout & Package

DO-214AC (SMA) package with cathode-indicated band marking; void-free thermosetting epoxy case (UL94V-0), matte-tin plated C-bend terminals solderable per MIL-STD-750 Method 2026; weight: 0.064 g.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ45AE3/TR13, SMAJ45AHE3/TR13 adds qualification-level screening without altering clamping behavior, while SMBJ45A-E3/52 increases surge capacity at the cost of board area - neither is pin-compatible, and both require layout revision or qualification justification.

Availability

SMAJ45AE3/TR13 is available at Aetrix Electronics and suitable for industrial automation, telecom infrastructure, and automotive electronics requiring stable component supply with RoHS compliance and surface-mount manufacturability.

Supply support for SMAJ45AE3/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 and mixed-signal components for defense, aerospace, and industrial markets.

The SMAJ series was engineered for robust, surface-mount transient suppression in harsh environments - targeting DC power rail and signal line protection where fast response, repeatable clamping, and thermal resilience are critical.

FAQ

What is the clamping voltage of SMAJ45AE3/TR13 under a 10/1000 µs surge?

The SMAJ45AE3/TR13 has a maximum clamping voltage (V_C) of 72.7 V when subjected to a 6.9 A peak pulse current with a 10/1000 µs waveform. This value is measured per Figure 2 in the official Microsemi datasheet MSC0270A and defines the upper voltage limit imposed on the protected circuit during surge events - critical for ensuring downstream ICs remain within their absolute maximum ratings.

Is SMAJ45AE3/TR13 unidirectional or bidirectional?

SMAJ45AE3/TR13 is a unidirectional TVS diode, indicated by the absence of "C" or "CA" in its part number suffix. It conducts in the forward direction (anode-to-cathode) during overvoltage events and blocks reverse current up to its 45 V standoff rating. The cathode is marked by a visible band on the DO-214AC package body, and it must be oriented with cathode toward the protected line and anode toward ground.

Does SMAJ45AE3/TR13 meet IEC61000-4-5 Class 3 lightning surge requirements?

Yes, SMAJ45AE3/TR13 is rated for IEC61000-4-5 Class 3 secondary lightning protection with a 42 Ω source impedance, covering devices with V_WM ≤ 24 V - however, its 45 V V_WM places it in Class 4 (V_WM ≤ 12 V) for 42 Ω testing. For 12 Ω source impedance, it qualifies for Class 2 (V_WM ≤ 16 V). Its 500 W rating supports validated performance across these classes when used with proper PCB layout and series impedance.

What is the thermal resistance of SMAJ45AE3/TR13 on a standard FR4 board?

SMAJ45AE3/TR13 has a thermal resistance of 80 °C/W junction-to-ambient when mounted on a standard FR4 printed circuit board with 1 oz copper and the recommended footprint per Microsemi's package drawing. Its junction-to-lead thermal resistance is 15 °C/W, enabling effective heat transfer to the PCB copper pour - essential for sustaining repetitive surge events without thermal runaway.

Can SMAJ45AE3/TR13 be used in lead-free reflow processes?

Yes, SMAJ45AE3/TR13 is RoHS-compliant with an "e3" suffix, indicating matte-tin plating qualified for lead-free reflow. It withstands peak temperatures up to 260 °C for 10 seconds per MIL-STD-750 Method 2026, making it compatible with standard SAC305 solder profiles. No pre-baking is required due to its IPC/JEDEC J-STD-020B Level 1 moisture sensitivity rating.