Vishay General Semiconductor - Diodes Division SMAJ550-M3/61

Overview

SMAJ550-M3/61 from Vishay General Semiconductor is a unidirectional surface-mount transient voltage suppressor (TVS) diode in SMA (DO-214AC) package, with 550 V breakdown voltage (V_BR), 495 V working peak reverse voltage (V_WM), and 300 W peak pulse power (P_PPM). It protects MOSFETs, ICs, and sensor signal lines against inductive switching transients and lightning-induced surges in automotive and industrial power electronics.

For engineers reviewing the SMAJ550-M3/61 datasheet, SMAJ550-M3/61 pinout, SMAJ550-M3/61 application, or SMAJ550-M3/61 equivalent, key selection criteria include clamping voltage at 400 mA (760 V), low leakage (<1.0 µA at V_WM), thermal resistance (R_θJA = 120 °C/W), AEC-Q101 qualification eligibility (via HM3 suffix), and UL 94 V-0 molding compound compliance.

Technical Context

The SMAJ550-M3/61 operates as a unidirectional avalanche diode with glass-passivated junction, optimized for fast response to transient overvoltages. Its clamping behavior follows a defined 10/1000 µs waveform, with VC = 760 V at IPP = 400 mA and incremental surge resistance contributing to predictable voltage limiting under surge conditions.

Thermal design relies on R_θJL = 30 °C/W (junction-to-lead) and R_θJA = 120 °C/W (junction-to-ambient), requiring PCB copper pad layout per Vishay's recommended 0.2" × 0.2" (5.0 mm × 5.0 mm) minimum for rated power dissipation. Temperature coefficient of V_BR is +650 mV/°C, directly impacting breakdown stability across operating temperature range (–55 °C to +150 °C).

Key Specifications

Pinout & Package

Package: SMA (DO-214AC), surface-mount, halogen-free, RoHS-compliant, UL 94 V-0 rated molding compound. Cathode indicated by color band. Matte tin-plated leads, J-STD-002 solderable.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ550-M3/61, SMAJ530-M3/61 offers earlier conduction onset for lower-voltage systems, while SMBJ550A-M3/61 trades smaller size for better thermal derating - both require layout review due to differing footprints and thermal profiles.

Availability

SMAJ550-M3/61 is available at Aetrix Electronics and suitable for automotive power rail protection, industrial sensor interface circuits, telecom DC input stages, and consumer appliance motor drive designs requiring stable component supply and consistent surge immunity performance.

Supply support for SMAJ550-M3/61 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, and protection devices with emphasis on reliability, ruggedness, and application-specific optimization.

The SMAJ series is designed for high-energy transient suppression in space-constrained surface-mount applications, targeting automotive, industrial, and telecom systems where robustness against inductive and lightning-induced surges is mission-critical.

FAQ

What is the maximum clamping voltage of the SMAJ550-M3/61 under standard test conditions?

The SMAJ550-M3/61 has a maximum clamping voltage (V_C) of 760 V when subjected to a 400 mA, 10/1000 µs transient waveform. This value is measured per JEDEC standards and defines the upper voltage limit imposed on protected circuitry during surge events. The SMAJ550-M3/61 maintains this clamping performance across its specified operating temperature range, ensuring predictable protection behavior in real-world deployments.

Is the SMAJ550-M3/61 suitable for automotive applications?

The SMAJ550-M3/61 itself is industrial-grade; however, the AEC-Q101 qualified variant SMAJ550HM3_B/H is available for automotive use. While the SMAJ550-M3/61 shares identical electrical characteristics and package, it lacks the extended stress testing required for automotive qualification. For under-hood or safety-critical systems, engineers must specify the HM3 suffix version - the SMAJ550-M3/61 remains appropriate for non-automotive industrial or telecom applications where AEC-Q101 is not mandated.

What does the "/61" suffix indicate in SMAJ550-M3/61?

Within the Vishay ordering system, the "/61" suffix in SMAJ550-M3/61 denotes the preferred package code for 7-inch diameter plastic tape-and-reel delivery, containing 1800 units per reel. This packaging format is optimized for automated SMT placement equipment and ensures consistent feed reliability. The SMAJ550-M3/61 is distinct from variants like /5A (13-inch reel, 7500 units) or HM3_B/I (AEC-Q101, 13-inch reel), and all share identical electrical specs and SMA (DO-214AC) mechanical form.

How does the junction capacitance of SMAJ550-M3/61 affect high-speed signal lines?

The SMAJ550-M3/61 exhibits 90 pF junction capacitance at 0 V bias, which may introduce signal attenuation or timing skew on high-speed digital lines (e.g., USB, HDMI). It is best applied on moderate-bandwidth paths such as analog sensor outputs, CAN/LIN buses, or DC power rails where bandwidth impact is negligible. For >10 MHz signal integrity, lower-capacitance TVS devices (e.g., <10 pF) should be selected - the SMAJ550-M3/61 is not intended for RF or high-speed serial interface protection.

What thermal considerations apply when using SMAJ550-M3/61 in continuous operation?

The SMAJ550-M3/61 has a thermal resistance of R_θJA = 120 °C/W under standard PCB mounting (0.2" × 0.2" copper pads). At its rated DC power dissipation of 2.5 W, junction temperature rise can exceed 300 °C - well beyond the 150 °C absolute maximum. Therefore, the SMAJ550-M3/61 is intended only for transient, non-repetitive surge suppression, not steady-state power dissipation. Continuous operation requires strict adherence to derating curves in Figure 2 of the datasheet to avoid thermal runaway.