Vishay General Semiconductor - Diodes Division SMAJ54CAHE3_A/H

Overview

SMAJ54CAHE3_A/H from Vishay General Semiconductor is a bidirectional transient voltage suppressor (TVS) diode in SMA (DO-214AC) package, designed for clamping voltage transients on signal and power lines. It features a 54 V standoff voltage (V_WM), 60.0–66.3 V breakdown voltage (V_BR) at 1 mA, 400 W peak pulse power (10/1000 μs), and clamps to ≤87.1 V at 4.6 A peak surge current - deployed in automotive sensor interfaces and industrial I/O protection.

For engineers reviewing the SMAJ54CAHE3_A/H datasheet, SMAJ54CAHE3_A/H pinout, SMAJ54CAHE3_A/H application, or SMAJ54CAHE3_A/H equivalent, key selection criteria include bidirectional clamping capability, AEC-Q101 qualification, 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 device operates as a voltage-clamped shunt protector: during overvoltage events exceeding V_WM = 54 V, it avalanches symmetrically in both directions to limit transient voltage across protected circuitry. Its glass-passivated junction ensures stable breakdown characteristics and fast response (<1 ns), while the unmarked SMA package reflects its bidirectional polarity.

Thermal performance is defined by R_θJA = 120 °C/W (on standard pad layout) and R_θJL = 30 °C/W, enabling reliable operation up to T_J = 150 °C. It meets J-STD-020 MSL Level 1 and supports lead-free reflow up to 260 °C peak.

Key Specifications

Pinout & Package

Package: SMA (DO-214AC), bidirectional configuration with no polarity marking; terminals are matte tin-plated leads compliant with J-STD-002 and JESD 22-B102 solderability standards.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ54CAHE3_A/H, SMAJ54CA-M3/61 offers identical protection performance with halogen-free construction, while SMCJ54CAHE3_A/H delivers 3.75× higher pulse power in a physically larger package - choice depends on board space, environmental compliance, and system-level surge test requirements.

Availability

SMAJ54CAHE3_A/H is available at Aetrix Electronics and suitable for automotive sensor interfaces, industrial PLC I/O modules, consumer power adapter outputs, and telecom line interfaces requiring stable component supply with AEC-Q101 assurance and lead-free manufacturing support.

Supply support for SMAJ54CAHE3_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, precision, and application-specific optimization.

The SMAJ series is engineered for robust transient suppression in space-constrained, high-reliability applications - particularly targeting automotive, industrial, and telecom systems where bidirectional clamping and AEC-Q101 validation are mandatory.

FAQ

What is the clamping voltage of SMAJ54CAHE3_A/H at its rated peak pulse current?

The SMAJ54CAHE3_A/H clamps to a maximum of 87.1 V at its specified peak pulse current of 4.6 A (10/1000 μs waveform). This value is measured under standardized test conditions and defines the upper voltage limit imposed on protected circuitry during surge events. The clamping voltage is critical for ensuring downstream components like microcontrollers or transceivers remain within their absolute maximum ratings. SMAJ54CAHE3_A/H maintains this performance consistently across its qualified operating temperature range.

Is SMAJ54CAHE3_A/H suitable for automotive applications?

Yes, SMAJ54CAHE3_A/H is AEC-Q101 qualified and explicitly designated for automotive use with ordering code suffix "HE3". It undergoes rigorous stress testing including temperature cycling, highly accelerated life testing (HALT), and ESD verification per AEC standards. Its 150 °C maximum junction temperature, MSL Level 1 rating, and bidirectional clamping make it appropriate for under-hood and cabin-mounted ECUs, sensor modules, and infotainment power rails. SMAJ54CAHE3_A/H meets automotive OEM requirements for long-term reliability in harsh environments.

How does the bidirectional design of SMAJ54CAHE3_A/H affect its circuit implementation?

The bidirectional design of SMAJ54CAHE3_A/H means it functions identically regardless of voltage polarity - no cathode marking is present, and either terminal may serve as anode or cathode depending on transient direction. This eliminates orientation concerns during automated placement and simplifies PCB layout for AC-coupled or differential signal lines. Unlike unidirectional TVS diodes, SMAJ54CAHE3_A/H provides symmetrical clamping on both positive and negative excursions, making it ideal for protecting balanced interfaces such as RS-485, CAN, or telecom line pairs without requiring dual-device configurations.

What is the thermal resistance of SMAJ54CAHE3_A/H, and how does it impact PCB layout?

SMAJ54CAHE3_A/H has a typical junction-to-ambient thermal resistance (R_θJA) of 120 °C/W when mounted on the minimum recommended 0.2" × 0.2" (5.0 mm × 5.0 mm) copper pads per terminal. This value assumes standard FR-4 board thickness and no internal copper planes. To maintain safe junction temperatures under sustained power dissipation or repeated surges, designers must adhere to Vishay's specified pad layout and avoid excessive trace narrowing. SMAJ54CAHE3_A/H also exhibits R_θJL = 30 °C/W, indicating efficient heat transfer from junction to leads - reinforcing the importance of adequate copper area for thermal relief.

Does SMAJ54CAHE3_A/H require derating above 25 °C ambient temperature?

Yes, SMAJ54CAHE3_A/H requires derating of its peak pulse power capability above 25 °C ambient temperature, as shown in Figure 2 of the Vishay datasheet (Document Number: 88390). The device's 400 W rating applies only at T_A = 25 °C; power handling decreases linearly with rising ambient, reaching approximately 70 % of rated value at 85 °C. This derating is essential for accurate surge margin calculation in real-world applications such as engine compartments or enclosed industrial enclosures. SMAJ54CAHE3_A/H data sheet provides precise derating curves to support thermal design validation.