Vishay General Semiconductor - Diodes Division SMAJ550-M3/5A

Overview

SMAJ550-M3/5A from Vishay General Semiconductor is a unidirectional surface-mount Transient Voltage Suppressor (TVS) diode designed for high-voltage transient protection in power and signal lines. It features a 550 V breakdown voltage (V_BR), 495 V stand-off voltage (V_WM), 760 V clamping voltage at 400 mA, 300 W peak pulse power (10/1000 µs), and operates up to +150 °C junction temperature - deployed in automotive power electronics and industrial sensor interfaces.

For engineers reviewing the SMAJ550-M3/5A datasheet, SMAJ550-M3/5A pinout, SMAJ550-M3/5A application, or SMAJ550-M3/5A equivalent, key selection criteria include unidirectional polarity, DO-214AC (SMA) package compatibility, clamping performance under 400 mA surge, thermal resistance (R_θJA = 120 °C/W), and AEC-Q101 qualification path via HM3 variant.

Technical Context

This TVS diode uses a glass-passivated silicon junction to achieve fast response (<1 ns) and low incremental surge resistance. Its unidirectional architecture provides reverse-biased clamping only, with breakdown specified at 100 µA test current and clamping validated per 10/1000 µs waveform.

Thermal design relies on PCB copper pad layout per JEDEC standards: R_θJL = 30 °C/W (junction-to-lead) and R_θJA = 120 °C/W (junction-to-ambient) assume minimum recommended pads. The device meets MSL Level 1 and JESD201 Class 2 whisker resistance.

Key Specifications

Pinout & Package

Package: SMA (DO-214AC), surface-mount, unidirectional polarity with cathode band marking. Matte tin-plated leads, RoHS-compliant, halogen-free, M3 suffix.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ550-M3/5A, SMAJ55A-M3/5A serves lower-voltage domains with identical form factor but inadequate standoff for 400+ V systems, while SMCJ550A-M3/57 delivers 5× higher surge power in a physically larger package - requiring PCB redesign but enabling robust front-end clamping.

Availability

SMAJ550-M3/5A is available at Aetrix Electronics and suitable for automotive power modules, industrial motor drives, telecom infrastructure equipment, and renewable energy inverters requiring stable component supply and consistent halogen-free, RoHS-compliant sourcing.

Supply support for SMAJ550-M3/5A 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, thermal performance, and automotive-grade validation.

The SMAJ series targets high-voltage transient suppression in harsh environments, engineered for fast clamping, stable parametric drift, and seamless integration into automated SMT assembly lines using standard DO-214AC footprints.

FAQ

What is the maximum clamping voltage of SMAJ550-M3/5A under standard test conditions?

The SMAJ550-M3/5A has a maximum clamping voltage (V_C) of 760 V when subjected to a 400 mA, 10/1000 µs surge waveform per the Vishay datasheet. This value defines the upper voltage limit imposed on protected circuitry during transient events and is measured with the device mounted on minimum recommended PCB copper pads. The SMAJ550-M3/5A achieves this clamping performance while maintaining unidirectional polarity and DO-214AC packaging.

Is SMAJ550-M3/5A suitable for automotive applications?

SMAJ550-M3/5A itself is industrial-grade; however, its AEC-Q101-qualified variant SMAJ550HM3_X is certified for automotive use. The base SMAJ550-M3/5A shares identical electrical specs and DO-214AC packaging but lacks the extended reliability testing required for automotive qualification. For production automotive designs, engineers should specify the HM3 suffix version. The SMAJ550-M3/5A remains appropriate for industrial and telecom applications where AEC-Q101 is not mandated.

What does the "M3/5A" suffix indicate in SMAJ550-M3/5A?

The "M3" suffix denotes halogen-free, RoHS-compliant construction and JESD201 Class 2 whisker resistance; "5A" specifies the packaging format: 7500 units per 13-inch plastic tape-and-reel. This differs from "/61", which indicates 1800 units per 7-inch reel. Both variants share identical electrical and thermal characteristics. The SMAJ550-M3/5A is fully compatible with standard SMA footprint layouts and reflow profiles defined in J-STD-020.

How does the thermal resistance of SMAJ550-M3/5A affect PCB layout?

SMAJ550-M3/5A has R_θJA = 120 °C/W and R_θJL = 30 °C/W, meaning effective heat dissipation depends heavily on copper pad area and thickness. Vishay specifies performance based on 0.2" × 0.2" (5.0 mm × 5.0 mm) copper pads per terminal. Reducing pad size increases junction temperature, risking premature failure during repeated surges. The SMAJ550-M3/5A must be routed with adequate thermal copper to maintain T_J ≤ 150 °C under worst-case duty cycles.

Can SMAJ550-M3/5A be used in bidirectional configurations?

No - SMAJ550-M3/5A is strictly unidirectional, as confirmed by Vishay's datasheet and device marking (cathode band). It conducts only when the cathode is at higher potential than the anode, making it unsuitable for AC line protection or symmetric transient suppression. For bidirectional operation, engineers must select a dedicated bidirectional TVS such as SMBJ550A-M3/57 or use back-to-back unidirectional devices. The SMAJ550-M3/5A's design intentionally omits symmetrical clamping capability to optimize V_BR precision and leakage performance.