Vishay General Semiconductor - Diodes Division SMAJ550HM3_A/H

Overview

SMAJ550HM3_A/H from Vishay General Semiconductor is a unidirectional surface-mount transient voltage suppressor (TVS) diode in SMA (DO-214AC) package, designed for robust overvoltage protection of sensitive electronics. It features a 55 V standoff voltage (V_WM), 61.1 V minimum breakdown voltage (V_BR), 96.8 V maximum clamping voltage (V_C) at 4.1 A peak pulse current, and 400 W peak pulse power rating with 10/1000 μs waveform - deployed on power rails and signal lines in automotive ECUs and industrial sensor interfaces.

For engineers reviewing the SMAJ550HM3_A/H datasheet, SMAJ550HM3_A/H pinout, SMAJ550HM3_A/H application, or SMAJ550HM3_A/H equivalent, key selection criteria include its AEC-Q101 qualification, halogen-free RoHS compliance, 150 °C max junction temperature, low incremental surge resistance, and compatibility with automated SMT placement on 0.2" × 0.2" copper pads.

Technical Context

This TVS diode operates as a unidirectional clamping device, leveraging an avalanche breakdown mechanism to limit transient overvoltages before they damage downstream ICs or MOSFETs. Its glass-passivated junction ensures stable electrical characteristics and high reliability under repetitive surge stress.

The SMAJ550HM3_A/H is rated for 400 W peak pulse power (10/1000 μs), derated to 300 W above 78 V, with thermal resistance of 120 °C/W (junction-to-ambient) and 30 °C/W (junction-to-lead), enabling effective heat dissipation in compact PCB layouts without forced cooling.

Key Specifications

Pinout & Package

Package: SMA (DO-214AC), molded plastic case with matte tin-plated leads, MSL Level 1 (per J-STD-020), LF peak reflow temperature 260 °C. Polarity indicated by cathode band on unidirectional devices.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ550HM3_A/H, SMAJ55AHE3_A/H offers identical clamping performance but lacks halogen-free construction and automotive qualification, while SMAJ55AHM3_A/I provides identical functionality in a higher-volume tape-and-reel format - enabling direct substitution where packaging logistics align.

Availability

SMAJ550HM3_A/H is available at Aetrix Electronics and suitable for automotive electronic control units, industrial sensor interfaces, and telecom DC bias protection requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for SMAJ550HM3_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, TVS devices, and optoelectronics with emphasis on reliability and application-specific performance.

The SMAJ series is engineered for high-energy transient suppression in harsh environments - targeting automotive, industrial, and telecom applications where robustness, AEC-Q101 compliance, and precise clamping are critical.

FAQ

What is the clamping voltage of SMAJ550HM3_A/H at its rated peak pulse current?

The SMAJ550HM3_A/H has a maximum clamping voltage (V_C) of 96.8 V at its peak pulse current (I_PPM) of 4.1 A, measured using the standard 10/1000 μs waveform. This value defines the upper voltage limit imposed on protected circuitry during surge events and is confirmed in Vishay's official datasheet revision 09-Jan-2024 (Document Number: 88390). The SMAJ550HM3_A/H maintains this clamping performance across its full operating temperature range.

Is SMAJ550HM3_A/H qualified for automotive applications?

Yes, SMAJ550HM3_A/H is AEC-Q101 qualified, as explicitly stated in the Vishay datasheet under "Mechanical Data" and "Ordering Information". The "HM3" suffix denotes halogen-free, RoHS-compliant, and AEC-Q101-qualified construction. This qualification covers stress tests including temperature cycling, high-temperature reverse bias, and ESD, making SMAJ550HM3_A/H suitable for under-hood and chassis-mounted automotive electronics.

What does the "_A/H" suffix mean in SMAJ550HM3_A/H?

The "_A/H" suffix in SMAJ550HM3_A/H indicates the revision code ("A") and packaging configuration ("H" = 7-inch diameter plastic tape and reel, 1800 pieces per reel), per Vishay's ordering information table. This is distinct from the base part's functional designation and does not affect electrical or thermal specifications. The SMAJ550HM3_A/H shares identical performance, qualification, and reliability data with other HM3 variants differing only in reel size or revision level.

Can SMAJ550HM3_A/H be used in bidirectional configurations?

No, SMAJ550HM3_A/H is a unidirectional TVS diode, as confirmed by its part number structure (no "CA" suffix) and datasheet labeling. Bidirectional variants carry the "CA" suffix (e.g., SMAJ55CA). Using SMAJ550HM3_A/H in bidirectional applications would leave the forward-conducting path unprotected; for AC or dual-polarity signal lines, a dedicated bidirectional device or back-to-back unidirectional pair must be selected instead.

What is the thermal resistance of SMAJ550HM3_A/H, and how does it impact PCB layout?

SMAJ550HM3_A/H has a typical junction-to-ambient thermal resistance (R_θJA) of 120 °C/W and junction-to-lead resistance (R_θJL) of 30 °C/W, measured on 0.2" × 0.2" copper pads per terminal. To maintain safe junction temperatures under repeated surges, PCB layout must provide adequate copper area and minimize trace length - especially for the cathode connection - and avoid thermal isolation. The SMAJ550HM3_A/H is not intended for use without defined pad geometry per the datasheet mounting recommendations.