Microchip Technology SMAJ8.5AE3/TR13

Overview

SMAJ8.5AE3/TR13 from Microsemi is a unidirectional surface-mount transient voltage suppressor (TVS) designed for primary and secondary surge protection in DC power rails and signal lines. It features a 8.5 V working peak standoff voltage (V_WM), 9.44 V minimum breakdown voltage (V_BR), 15.9 V maximum clamping voltage (V_C) at 31.4 A peak pulse current, and 500 W peak pulse power rating per 10/1000 µs waveform - used in industrial power supplies and automotive body electronics.

For engineers reviewing the SMAJ8.5AE3/TR13 datasheet, SMAJ8.5AE3/TR13 pinout, SMAJ8.5AE3/TR13 application, or SMAJ8.5AE3/TR13 equivalent, key selection criteria include clamping voltage margin relative to protected IC V_CC, IEC 61000-4-2/4-4/4-5 compliance level, unidirectional polarity requirement, and DO-214AC package thermal performance on FR4 PCBs.

Technical Context

This TVS operates as a silicon avalanche diode with fast response (<100 ps theoretical turn-on) and low dynamic impedance during transients. Its unidirectional construction provides forward conduction capability (40 A surge, 3.5 V max forward voltage) and reverse-biased clamping action above V_BR, enabling protection of downstream CMOS/BiCMOS ICs without forward-path interference.

It meets IEC 61000-4-2 Level 4 (±15 kV contact), IEC 61000-4-4 (4 kV EFT), and IEC 61000-4-5 secondary lightning (Class 4, 12 Ω source, 1 kA test) when applied with proper PCB layout and grounding. The device is rated for -65°C to +150°C operation and exhibits <1 μA standby leakage at V_WM.

Key Specifications

Pinout & Package

DO-214AC (SMA) package with cathode-indicated band marking; two-terminal unidirectional configuration. Thermal resistance is 15 °C/W junction-to-lead and 80 °C/W junction-to-ambient on FR4 (1 oz Cu) with recommended footprint.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ8.5AE3/TR13, SMAJ8.5AHE3/TR13 adds avionics-level screening without changing electrical behavior, while SMBJ8.5A-E3/52 trades smaller footprint for higher power and improved thermal resistance - neither is pin-compatible, but both serve overlapping protection functions in different mechanical or reliability contexts.

Availability

SMAJ8.5AE3/TR13 is available at Aetrix Electronics and suitable for industrial power supplies, automotive body electronics, telecom remote powering, and medical diagnostic equipment requiring stable component supply with RoHS compliance and consistent DO-214AC packaging.

Supply support for SMAJ8.5AE3/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 aerospace, defense, and industrial markets.

The SMAJ series was developed specifically for robust, surface-mount transient suppression in space-constrained, high-surge environments - emphasizing fast response, stable clamping, and proven IEC compliance across wide temperature ranges.

FAQ

What is the clamping voltage of SMAJ8.5AE3/TR13 at its rated peak pulse current?

The SMAJ8.5AE3/TR13 has a maximum clamping voltage (V_C) of 15.9 V at 31.4 A peak pulse current (I_PP) under the standard 10/1000 µs waveform. This value is measured per Figure 2 in the official Microsemi datasheet MSC0270A and defines the highest voltage the protected circuit will experience during a full-rated surge event. Designers must ensure this clamping level remains below the absolute maximum ratings of downstream ICs.

Is SMAJ8.5AE3/TR13 unidirectional or bidirectional, and how is polarity marked?

SMAJ8.5AE3/TR13 is a unidirectional TVS diode, indicated by the "A" suffix in its part number. Polarity is marked by a cathode band on the DO-214AC package body - the banded end connects to system ground, while the anode connects to the line being protected. Bidirectional variants use "C" or "CA" suffixes (e.g., SMAJ8.5CA), which lack polarity marking and clamp in both directions.

Does SMAJ8.5AE3/TR13 meet IEC 61000-4-5 for secondary lightning protection?

Yes, SMAJ8.5AE3/TR13 is certified for secondary lightning protection per IEC 61000-4-5 with 12 Ω source impedance at Class 4 (1 kA test current), as confirmed in the Microsemi datasheet MSC0270A. Its 500 W peak pulse power and 15.9 V clamping voltage enable compliance when mounted with low-inductance grounding on FR4 PCBs using the recommended pad layout.

What is the maximum steady-state power dissipation of SMAJ8.5AE3/TR13 on a standard FR4 board?

When mounted on an FR4 printed circuit board with 1 oz copper and the recommended footprint, SMAJ8.5AE3/TR13 dissipates up to 1.56 W continuously at ambient temperature (T_A = 25°C), or 5 W at lead temperature (T_L = 75°C). These values derive from its thermal resistance of 80 °C/W junction-to-ambient and 15 °C/W junction-to-lead, as specified in the Microsemi datasheet.

Can SMAJ8.5AE3/TR13 be used in automotive applications requiring AEC-Q200 qualification?

No, SMAJ8.5AE3/TR13 is not AEC-Q200 qualified. While it operates from -65°C to +150°C and is used in automotive body electronics, Microsemi does not list this specific variant under AEC-Q200 stress testing. For AEC-Q200-compliant alternatives, engineers should consider Microchip's automotive-qualified TVS families such as the AEC-Q200-certified SMAJ8.5A-Q, which undergoes additional temperature cycling and humidity testing.