Vishay General Semiconductor - Diodes Division SMAJ8.5AHM3_A/I

Overview

SMAJ8.5AHM3_A/I from Vishay General Semiconductor is a unidirectional surface-mount transient voltage suppressor (TVS) diode in SMA (DO-214AC) package, designed to protect sensitive electronics against ESD, lightning-induced surges, and inductive switching transients. It features a 8.5 V stand-off voltage (VWM), 9.44–10.4 V breakdown voltage (VBR) at 1 mA, 14.4 V maximum clamping voltage (VC) at 27.8 A peak pulse current (IPPM), and 400 W peak pulse power rating with 10/1000 μs waveform - used in automotive sensor signal lines, industrial I/O protection, and DC power rail clamping.

For engineers reviewing the SMAJ8.5AHM3_A/I datasheet, SMAJ8.5AHM3_A/I pinout, SMAJ8.5AHM3_A/I application, or SMAJ8.5AHM3_A/I equivalent, key selection criteria include unidirectional polarity, AEC-Q101 qualification (HM3 suffix), halogen-free RoHS compliance, MSL Level 1 moisture sensitivity, and thermal resistance (RθJA = 120 °C/W) for PCB layout thermal management.

Technical Context

This TVS diode operates as a voltage-clamped shunt protector: under normal bias it presents high impedance (<1 μA leakage at 8.5 V), then rapidly avalanches below 1 ns to clamp transient overvoltage to ≤14.4 V at 27.8 A. Its glass-passivated junction ensures stable breakdown and low incremental surge resistance.

The device is rated for repetitive 10/1000 μs surges at 0.01% duty cycle (400 W up to 78 V; derated to 300 W above), with operating junction temperature range of −55 °C to +150 °C and peak forward surge current capability of 40 A (8.3 ms half-sine).

Key Specifications

Pinout & Package

Package: SMA (DO-214AC), surface-mount, low-profile case with matte tin-plated leads solderable per J-STD-002; cathode indicated by band marking.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ8.5AHM3_A/I, the HE3 variant lacks halogen-free certification and AEC-Q101 validation, limiting its use in automotive programs; the M3/5A variant offers identical performance in a different reel format but requires cross-checking of packaging codes in ERP systems.

Availability

SMAJ8.5AHM3_A/I is available at Aetrix Electronics and suitable for automotive sensor protection, industrial I/O interface hardening, and DC power rail clamping requiring stable component supply, long-term lifecycle support, and AEC-Q101 compliance.

Supply support for SMAJ8.5AHM3_A/I 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 and application-specific performance.

The SMAJ series is part of Vishay's TRANSZORB® TVS platform, engineered specifically for high-energy transient suppression in automotive, industrial, and telecom infrastructure where robustness and qualification compliance are mandatory.

FAQ

What is the clamping voltage of SMAJ8.5AHM3_A/I at its rated peak pulse current?

The SMAJ8.5AHM3_A/I has a maximum clamping voltage (VC) of 14.4 V at its rated peak pulse current (IPPM) of 27.8 A, measured using the standard 10/1000 μs double-exponential waveform. This value ensures downstream ICs experience limited overvoltage stress during surge events, making SMAJ8.5AHM3_A/I suitable for protecting 5 V and 12 V systems where voltage margins are tight.

Is SMAJ8.5AHM3_A/I qualified for automotive applications?

Yes, SMAJ8.5AHM3_A/I is AEC-Q101 qualified, as confirmed by the HM3 suffix in its ordering code. This qualification validates its reliability under automotive temperature cycling, humidity, mechanical shock, and lifetime surge stress conditions. Engineers deploying SMAJ8.5AHM3_A/I in engine control units, body control modules, or ADAS sensor interfaces can rely on its certified performance per SMAJ8.5AHM3_A/I datasheet specifications.

What does the "HM3" suffix indicate in SMAJ8.5AHM3_A/I?

The "HM3" suffix in SMAJ8.5AHM3_A/I denotes halogen-free, RoHS-compliant construction with AEC-Q101 qualification. It distinguishes this variant from E3 (RoHS only) and HE3 (RoHS + AEC-Q101, but not halogen-free). The "_A/I" portion specifies packaging: "A" is the revision code, and "I" indicates 13-inch tape-and-reel (7500 pcs). This coding ensures precise material and compliance traceability for SMAJ8.5AHM3_A/I in regulated supply chains.

How does SMAJ8.5AHM3_A/I compare to bidirectional TVS diodes like SMAJ8.5CA?

SMAJ8.5AHM3_A/I is unidirectional and intended for DC-biased lines where polarity is fixed (e.g., 12 V supply to ground), offering lower leakage and higher surge capability than its bidirectional counterpart SMAJ8.5CA. The latter supports AC-coupled or polarity-agnostic signals but exhibits higher ID at VWM and reduced PPPM above 78 V. For SMAJ8.5AHM3_A/I applications involving automotive power rails or sensor outputs referenced to ground, unidirectional operation provides superior protection efficiency and lower standby current.

What PCB layout guidance applies to SMAJ8.5AHM3_A/I for optimal thermal and surge performance?

To achieve rated 400 W peak pulse power, SMAJ8.5AHM3_A/I must be mounted on minimum 0.2" × 0.2" (5.0 mm × 5.0 mm) copper pads per terminal, per Vishay's recommended pad layout. Thermal resistance RθJA = 120 °C/W assumes this copper area; reducing pad size increases junction temperature and de-rates surge capability. Additionally, short, wide traces to ground minimize inductance and preserve sub-ns response - critical for SMAJ8.5AHM3_A/I to clamp before transient energy couples into protected circuitry.