Vishay General Semiconductor - Diodes Division SMAJ75CAHM3_A/H

Overview

SMAJ75CAHM3_A/H from Vishay General Semiconductor is a bidirectional transient voltage suppressor (TVS) diode in SMA (DO-214AC) package, designed for robust overvoltage protection of sensitive electronics. It features a 75 V standoff voltage (V_WM), 83.3–92.1 V breakdown voltage (V_BR) at 1 mA, 121 V maximum clamping voltage (V_C) at 3.3 A peak pulse current, and 400 W peak pulse power rating (10/1000 μs waveform). It is widely deployed to protect MOSFETs, ICs, and sensor signal lines in automotive and industrial power supply interfaces.

For engineers reviewing the SMAJ75CAHM3_A/H datasheet, SMAJ75CAHM3_A/H pinout, SMAJ75CAHM3_A/H application, or SMAJ75CAHM3_A/H equivalent, key selection criteria include bidirectional clamping behavior, AEC-Q101 qualification (via HM3 suffix), halogen-free RoHS compliance, MSL Level 1 moisture sensitivity, and compatibility with automated SMT placement on standard PCB copper pad layouts.

Technical Context

This device operates as a silicon avalanche diode optimized for fast transient suppression-responding in <1 ps-with low incremental surge resistance and excellent clamping ratio (V_C/V_BR ≈ 1.31 at rated conditions). Its bidirectional symmetry ensures identical electrical characteristics in both polarities, eliminating polarity concerns in AC-coupled or floating signal paths.

Thermally, it exhibits R_θJA = 120 °C/W (typ.) and R_θJL = 30 °C/W (typ.), enabling reliable operation up to T_J = +150 °C. The 40 A IFSM rating supports high-energy surge events, while its glass-passivated junction ensures long-term stability under repetitive transients.

Key Specifications

Pinout & Package

Package: SMA (DO-214AC), molded plastic case with matte tin-plated leads, UL 94 V-0 rated compound, no polarity marking for bidirectional configuration.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ75CAHE3_A/H, the SMAJ75CAHM3_A/H adds halogen-free construction and AEC-Q101 qualification-critical for Tier 1 automotive suppliers-while retaining identical clamping performance. Against SMAJ75AHE3_A/H, it provides true bidirectional symmetry essential for AC-coupled or floating interfaces without external polarity management.

Availability

SMAJ75CAHM3_A/H is available at Aetrix Electronics and suitable for automotive infotainment power rails, industrial PLC analog I/O modules, consumer USB-C port protection, and telecom DSL line interfaces requiring stable component supply across multi-year production cycles.

Supply support for SMAJ75CAHM3_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 targets board-level transient protection in harsh environments-designed for rapid response, repeatable clamping, and seamless integration into automotive, industrial, and telecom power and signal paths.

FAQ

What does the "HM3" suffix indicate in SMAJ75CAHM3_A/H?

The "HM3" suffix denotes halogen-free, RoHS-compliant construction with AEC-Q101 qualification. This means SMAJ75CAHM3_A/H meets automotive-grade reliability standards-including temperature cycling, highly accelerated life testing, and ESD immunity-while eliminating brominated flame retardants per JEDEC J-STD-20. It is certified for use in passenger vehicle ECUs and ADAS modules where material compliance and long-term field reliability are mandatory.

Is SMAJ75CAHM3_A/H suitable for protecting 75 V DC power rails?

Yes, SMAJ75CAHM3_A/H is specifically designed for this use case. Its 75 V standoff voltage (V_WM) allows continuous operation at nominal 75 V DC, while its 83.3–92.1 V breakdown range and 121 V clamping voltage ensure robust protection against transients exceeding system voltage-such as load dump spikes in industrial 75 V battery systems-without false triggering during normal operation.

How does SMAJ75CAHM3_A/H differ from unidirectional variants like SMAJ75AHE3_A/H?

SMAJ75CAHM3_A/H is bidirectional, meaning it clamps symmetrically for both positive and negative voltage transients-ideal for AC-coupled signals, floating buses, or dual-polarity supplies. In contrast, SMAJ75AHE3_A/H is unidirectional with a cathode band and only clamps in reverse bias; using it in bidirectional applications risks failure during negative excursions. SMAJ75CAHM3_A/H eliminates polarity dependency and simplifies layout.

What is the thermal performance of SMAJ75CAHM3_A/H under sustained power dissipation?

SMAJ75CAHM3_A/H has a typical junction-to-ambient thermal resistance (R_θJA) of 120 °C/W on standard 0.2" × 0.2" copper pads. At its rated DC power dissipation of 3.3 W, this yields a ~396 °C junction rise above ambient-so it is intended only for transient, not continuous, power handling. For steady-state conditions, derating per Figure 2 in the datasheet is required; actual safe operating area depends on PCB copper area and airflow.

Can SMAJ75CAHM3_A/H be used in IEC 61000-4-5 surge testing compliance designs?

Yes, SMAJ75CAHM3_A/H supports IEC 61000-4-5 compliance when properly applied. Its 400 W peak pulse power rating (10/1000 μs waveform) aligns with Level 3 (2 Ω source impedance, 1 kV line-earth) and Level 4 (40 Ω, 4 kV line-earth) test profiles. To meet full system-level immunity, it must be combined with appropriate PCB layout (short traces, low-inductance grounding) and upstream filtering-verified per application-specific test plans.