Vishay General Semiconductor - Diodes Division SMAJ8.5CA-E3/5A

Overview

SMAJ8.5CA-E3/5A from Vishay General Semiconductor is a bidirectional transient voltage suppressor (TVS) diode designed for robust overvoltage protection on signal and power lines. It features a 8.5 V stand-off voltage (V_WM), 9.44–10.4 V breakdown voltage (V_BR) at 1 mA, 14.4 V maximum clamping voltage (V_C) at 27.8 A peak pulse current, and 400 W peak pulse power rating with 10/1000 μs waveform - deployed in automotive sensor interfaces, industrial I/O protection, and USB/RS-485 line guarding.

For engineers reviewing the SMAJ8.5CA-E3/5A datasheet, SMAJ8.5CA-E3/5A pinout, SMAJ8.5CA-E3/5A application, or SMAJ8.5CA-E3/5A equivalent, key selection criteria include bidirectional clamping symmetry, low 14.4 V clamping at rated surge current, RoHS-compliant SMA (DO-214AC) package compatibility with automated SMT assembly, and AEC-Q101 qualification readiness via HE3 suffix variants.

Technical Context

This device operates as a voltage-clamped shunt protector: under normal conditions it presents high impedance (>100 MΩ at 8.5 V), but triggers into low-impedance conduction when transients exceed V_BR, diverting surge energy to ground. Its bidirectional architecture ensures identical clamping behavior in both polarities - critical for AC-coupled or floating signal paths like CAN bus stubs or differential sensor outputs.

Thermally, it uses a glass-passivated junction with 120 °C/W junction-to-ambient thermal resistance (R_θJA) and supports continuous power dissipation of 3.3 W at 50 °C ambient. The 0.073 %/°C temperature coefficient of V_BR ensures stable threshold drift across -55 °C to +150 °C operating range.

Key Specifications

Pinout & Package

Package: SMA (DO-214AC), molded plastic case with matte tin-plated leads, UL 94 V-0 rated compound, MSL Level 1 (260 °C reflow peak).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ8.5CA-E3/5A, the M3 variant offers identical protection performance with halogen-free construction, while SMAJ8.0CA-E3/5A trades 0.5 V higher stand-off margin for lower clamping voltage - enabling safer operation on 5 V systems but reducing noise immunity on 12 V lines.

Availability

SMAJ8.5CA-E3/5A is available at Aetrix Electronics and suitable for automotive sensor interfaces, industrial communication ports, and USB peripheral protection requiring stable component supply across production lifecycles.

Supply support for SMAJ8.5CA-E3/5A 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, TVS devices, and optoelectronics with emphasis on reliability and automotive qualification.

The SMAJ series was engineered for high-energy transient suppression in harsh environments - targeting automotive, industrial, and telecom infrastructure where robustness against load dump, EFT, and lightning surges is non-negotiable.

FAQ

What is the clamping voltage of SMAJ8.5CA-E3/5A at its rated peak pulse current?

The SMAJ8.5CA-E3/5A exhibits a maximum clamping voltage (V_C) of 14.4 V when subjected to its rated peak pulse current (I_PPM) of 27.8 A using the standardized 10/1000 μs waveform. This value is measured per JEDEC test conditions and ensures predictable overvoltage limiting for downstream circuitry. The SMAJ8.5CA-E3/5A maintains this clamping performance across its full operating temperature range (-55 °C to +150 °C).

Is SMAJ8.5CA-E3/5A suitable for automotive applications?

SMAJ8.5CA-E3/5A is RoHS-compliant and manufactured to Vishay's commercial-grade specifications; it is not AEC-Q101 qualified in the E3/5A configuration. However, the pin-compatible SMAJ8.5CAHE3 variant (with HE3 suffix) is fully AEC-Q101 qualified and shares identical electrical characteristics. For automotive use, specify SMAJ8.5CAHE3_X (where X = revision code) to ensure qualification compliance. The SMAJ8.5CA-E3/5A remains suitable for non-safety-critical automotive subsystems where qualification is not mandated.

How does the bidirectional design of SMAJ8.5CA-E3/5A affect its circuit placement?

The bidirectional design of SMAJ8.5CA-E3/5A eliminates polarity sensitivity - it functions identically regardless of orientation between protected line and ground. This allows direct placement across differential pairs (e.g., RS-485 A/B), AC-coupled signal paths, or floating references without cathode/anode alignment concerns. Unlike unidirectional TVS diodes, SMAJ8.5CA-E3/5A requires no band-marking verification during SMT assembly, simplifying layout and reducing misplacement risk.

What is the thermal resistance of SMAJ8.5CA-E3/5A, and how does it impact PCB layout?

SMAJ8.5CA-E3/5A has a typical junction-to-ambient thermal resistance (R_θJA) of 120 °C/W when mounted on minimum recommended copper pads (0.2" × 0.2" per terminal). To sustain repeated 400 W surges, designers must provide adequate copper area and avoid thermal isolation. Increasing pad size or adding internal ground planes reduces R_θJA, directly improving surge endurance. The SMAJ8.5CA-E3/5A's R_θJL of 30 °C/W also supports efficient heat transfer to PCB traces when used with thermally enhanced layouts.

Can SMAJ8.5CA-E3/5A be used to protect 5 V logic lines?

SMAJ8.5CA-E3/5A has a 8.5 V stand-off voltage (V_WM), making it unsuitable for direct protection of 5 V logic lines - its V_WM exceeds typical 5 V rail tolerances and risks leakage-induced power loss or false triggering. For 5 V systems, select SMAJ5.0CA-E3/5A (V_WM = 5.0 V) or SMAJ6.0CA-E3/5A (V_WM = 6.0 V). The SMAJ8.5CA-E3/5A is optimized for 12 V applications such as automotive body electronics or industrial 12 V I/O modules.