Vishay General Semiconductor - Diodes Division SMAJ45AHM3_A/H

Overview

SMAJ45AHM3_A/H from Vishay General Semiconductor is a unidirectional surface-mount Transient Voltage Suppressor (TVS) diode in SMA (DO-214AC) package, designed for clamping voltage transients on power and signal lines. It features a 45 V standoff voltage (V_WM), 50.0–55.3 V breakdown voltage (V_BR) at 1 mA, 72.7 V maximum clamping voltage (V_C) at 5.5 A peak pulse current, and 400 W peak pulse power rating with 10/1000 μs waveform - used to protect MOSFETs, ICs, and sensor interfaces in automotive and industrial power rails.

For engineers reviewing the SMAJ45AHM3_A/H datasheet, SMAJ45AHM3_A/H pinout, SMAJ45AHM3_A/H application, or SMAJ45AHM3_A/H equivalent, key selection criteria include unidirectional polarity, AEC-Q101 qualification (via HM3 suffix), halogen-free RoHS compliance, 150 °C max junction temperature, and compatibility with automated SMT placement on standard PCB copper pads.

Technical Context

This TVS diode operates as a fast-acting shunt clamp during overvoltage events, leveraging an avalanche breakdown mechanism to divert surge current away from protected circuitry. Its glass-passivated junction ensures stable leakage (<1.0 μA at V_WM) and low incremental surge resistance, enabling consistent clamping performance across repetitive transients.

The device is rated for 40 A non-repetitive forward surge current (8.3 ms half-sine), supports operation from –55 °C to +150 °C, and meets MSL Level 1 per J-STD-020 with 260 °C peak reflow profile - confirming suitability for high-reliability surface-mount assembly without moisture sensitivity concerns.

Key Specifications

Pinout & Package

Package: SMA (DO-214AC), molded plastic case with matte tin-plated leads, UL 94 V-0 rated compound, and polarity indicated by cathode band on unidirectional variants.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ45AHE3_A/H, the SMAJ45AHM3_A/H adds halogen-free construction and AEC-Q101 validation without altering clamping behavior or thermal limits; versus SMBJ45A-H, it trades peak power headroom for compact SMA packaging and direct drop-in compatibility in space-constrained designs.

Availability

SMAJ45AHM3_A/H is available at Aetrix Electronics and suitable for automotive ECU protection, industrial sensor interface hardening, and telecom DC-DC input stage surge suppression requiring stable component supply and full traceability.

Supply support for SMAJ45AHM3_A/H 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

Vishay General Semiconductor is a global leader in discrete semiconductors, specializing in diodes, rectifiers, MOSFETs, and protection devices with emphasis on reliability, efficiency, and application-specific optimization.

The SMAJ series is engineered for robust transient suppression in harsh environments - targeting automotive, industrial, and telecom systems where failure due to voltage surges must be eliminated through proven, standardized, and qualified components.

FAQ

What is the clamping voltage of the SMAJ45AHM3_A/H under a 10/1000 μs surge?

The SMAJ45AHM3_A/H has a maximum clamping voltage (V_C) of 72.7 V at 5.5 A peak pulse current (I_PPM) under the standardized 10/1000 μs waveform. This value is measured per Fig. 1 in Vishay Document 88390 and defines the upper voltage limit imposed on protected circuitry during transient events - critical for ensuring downstream ICs remain within their absolute maximum ratings. The SMAJ45AHM3_A/H achieves this with low incremental surge resistance and fast avalanche response.

Is the SMAJ45AHM3_A/H suitable for automotive applications?

Yes, the SMAJ45AHM3_A/H is AEC-Q101 qualified, as confirmed by its HM3 suffix and documentation in Vishay's 88390 datasheet. It is rated for operation from –55 °C to +150 °C, meets MSL Level 1, and is constructed with halogen-free, RoHS-compliant materials - making it appropriate for under-hood and body-control module applications. The SMAJ45AHM3_A/H is explicitly listed in Vishay's automotive ordering codes and validated for thermal cycling, mechanical shock, and humidity exposure per AEC-Q101 test conditions.

How does the SMAJ45AHM3_A/H differ from the SMAJ45A-E3 variant?

The SMAJ45AHM3_A/H differs from SMAJ45A-E3 in three key ways: it uses halogen-free molding compound (vs. standard RoHS), carries AEC-Q101 qualification (vs. commercial grade only), and employs the HM3 suffix denoting both attributes. Electrically, both share identical V_WM, V_BR, V_C, and P_PPM specs. The SMAJ45AHM3_A/H is intended for automotive-tier supply chains where halogen-free content and qualification are mandatory - whereas SMAJ45A-E3 serves general industrial or consumer use cases.

What is the thermal resistance of the SMAJ45AHM3_A/H, and how does it affect PCB layout?

The SMAJ45AHM3_A/H has a typical junction-to-ambient thermal resistance (R_θJA) of 120 °C/W and junction-to-lead (R_θJL) of 30 °C/W, per Vishay Document 88390. These values assume mounting on 0.2" × 0.2" (5.0 mm × 5.0 mm) copper pads per terminal. To maintain T_J ≤ 150 °C under 3.3 W steady-state dissipation, designers must provide adequate copper area and avoid excessive trace length - the SMAJ45AHM3_A/H relies on PCB copper for heat spreading rather than internal heatsinking.

Does the SMAJ45AHM3_A/H have polarity marking, and how is it identified?

Yes, the SMAJ45AHM3_A/H is unidirectional and features a visible cathode band on the SMA (DO-214AC) package body - located adjacent to the cathode terminal. Per Vishay's mechanical drawings and datasheet notes, this band identifies the high-side connection point for proper orientation during placement. Incorrect polarity (reversed installation) would prevent clamping action on positive transients and may lead to catastrophic failure under surge conditions. The SMAJ45AHM3_A/H cathode must connect to the protected line, and the anode to ground or return path.