Vishay General Semiconductor - Diodes Division SMAJ33A-M3/61

Overview

SMAJ33A-M3/61 from Vishay General Semiconductor is a unidirectional surface-mount Transient Voltage Suppressor (TVS) diode designed for robust overvoltage protection on DC power rails and signal lines. It features a 33 V standoff voltage (V_WM), 36.7–40.6 V breakdown range at 1 mA, clamps transients to ≤53.3 V at 7.5 A peak pulse current, and delivers 400 W peak pulse power (10/1000 μs waveform) - deployed in automotive power supply inputs and industrial sensor interface circuits.

For engineers reviewing the SMAJ33A-M3/61 datasheet, SMAJ33A-M3/61 pinout, SMAJ33A-M3/61 application, or SMAJ33A-M3/61 equivalent, key selection criteria include its unidirectional polarity, SMA (DO-214AC) package compatibility with automated SMT assembly, 150 °C max junction temperature, low 1.0 μA reverse leakage at V_WM, and halogen-free RoHS-compliant construction per M3 suffix.

Technical Context

This TVS diode operates as a clamping device in parallel with protected circuitry, entering avalanche conduction when transient voltage exceeds its breakdown threshold. Its glass-passivated silicon junction ensures stable V_BR tolerance (±5 % typical) and fast response time (<1 ns), enabling suppression of ESD, lightning-induced surges, and inductive switching spikes before downstream ICs are damaged.

The SMAJ33A-M3/61 is rated for 40 A non-repetitive forward surge current (8.3 ms half-sine), exhibits 0.100 %/°C temperature coefficient of V_BR, and maintains thermal resistance of 120 °C/W (junction-to-ambient) on standard 0.2" × 0.2" copper pads - confirming suitability for compact, thermally constrained PCB layouts without forced cooling.

Key Specifications

Pinout & Package

Package: SMA (DO-214AC), molded plastic case with matte tin-plated leads; cathode indicated by band on one end; meets UL 94 V-0 flammability rating and JESD 201 Class 2 whisker resistance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ33A-E3/61, the M3 suffix adds halogen-free assurance without performance trade-offs; versus SMAJ33CA-M3/61, the unidirectional version provides tighter leakage control and eliminates unnecessary bidirectional conduction paths in fixed-polarity DC systems.

Availability

SMAJ33A-M3/61 is available at Aetrix Electronics and suitable for automotive electronics, industrial sensor interfaces, and telecom power feed circuits requiring stable component supply, long-term lifecycle support, and halogen-free compliance.

Supply support for SMAJ33A-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, MOSFETs, optoelectronics, and passive components with emphasis on reliability, power efficiency, and automotive-grade qualification.

The SMAJ series is engineered for high-energy transient suppression in harsh environments - targeting design-in for automotive infotainment, industrial PLCs, and telecom infrastructure where robustness and AEC-Q101 readiness are mandatory.

FAQ

What is the maximum clamping voltage of the SMAJ33A-M3/61 under a 10/1000 μs surge?

The SMAJ33A-M3/61 clamps to a maximum of 53.3 V when subjected to its rated peak pulse current of 7.5 A using the standardized 10/1000 μs waveform. This value is measured per IEC 61000-4-5 and defines the upper voltage limit imposed on protected circuitry during surge events. The SMAJ33A-M3/61 achieves this clamping performance while maintaining low incremental surge resistance and sub-1 ns response time.

Does the SMAJ33A-M3/61 meet automotive qualification standards?

The SMAJ33A-M3/61 itself is commercial-grade and halogen-free RoHS-compliant, but Vishay offers the AEC-Q101 qualified variant as SMAJ33AHM3_X (with revision code). The base SMAJ33A-M3/61 shares identical electrical and thermal specifications with the qualified version - only the test documentation and traceability differ. For automotive use, specify the HM3 suffix with appropriate revision code to ensure full AEC-Q101 compliance for SMAJ33A-M3/61 derivatives.

How does the M3 suffix differ from E3 in SMAJ33A-M3/61?

The M3 suffix denotes halogen-free, RoHS-compliant construction meeting JESD201 Class 2 whisker resistance, while E3 indicates RoHS-compliance without halogen-free assurance. Both share identical electrical parameters, package dimensions, and thermal performance. The SMAJ33A-M3/61 is preferred for automotive, industrial, and green-electronics applications where halogen content restrictions apply - the SMAJ33A-M3/61 replaces E3 variants where regulatory or customer sustainability requirements mandate halogen-free materials.

Can SMAJ33A-M3/61 be used in bidirectional signal protection?

No - SMAJ33A-M3/61 is strictly unidirectional and must be oriented with cathode toward the protected line. For bidirectional protection (e.g., RS-485, CAN, AC signals), use SMAJ33CA-M3/61, which has symmetrical breakdown in both directions. Attempting to use SMAJ33A-M3/61 on AC or polarity-reversing lines results in forward conduction during negative half-cycles, causing failure. The SMAJ33A-M3/61 is optimized for DC rail and unidirectional signal clamping only.

What is the thermal resistance and recommended pad layout for SMAJ33A-M3/61?

The SMAJ33A-M3/61 has a typical junction-to-ambient thermal resistance (R_θJA) of 120 °C/W when mounted on 0.2" × 0.2" (5.0 mm × 5.0 mm) copper pads per terminal, per Vishay's standard test condition. To maintain reliability at full 400 W pulse rating, use minimum recommended pad layout per DO-214AC spec: 0.074" (1.88 mm) pad width, 0.208" (5.28 mm) pad length, and thermal vias if ambient exceeds 70 °C. The SMAJ33A-M3/61's R_θJL of 30 °C/W supports efficient heat transfer to PCB copper.