Vishay General Semiconductor - Diodes Division SMAJ85AHM3_A/H

Overview

SMAJ85AHM3_A/H from Vishay General Semiconductor is a unidirectional surface-mount Transient Voltage Suppressor (TVS) diode in SMA (DO-214AC) package, designed for clamping voltage transients on power and signal lines. It features 85 V standoff voltage (VWM), 94.4–104 V breakdown voltage (VBR) at 1 mA, 137 V maximum clamping voltage (VC) at 2.2 A peak pulse current, and 400 W peak pulse power (10/1000 μs waveform), targeting protection of MOSFETs, ICs, and sensor interfaces in automotive and industrial systems.

For engineers reviewing the SMAJ85AHM3_A/H datasheet, SMAJ85AHM3_A/H pinout, SMAJ85AHM3_A/H application, or SMAJ85AHM3_A/H equivalent, key selection criteria include unidirectional polarity, AEC-Q101 qualification status, thermal resistance (RθJA = 120 °C/W), junction temperature range (−55 to +150 °C), and compatibility with automated SMT placement on standard PCB copper pads.

Technical Context

This TVS diode operates as a clamping device that remains high-impedance below VWM (85 V) and rapidly transitions to low-impedance conduction above VBR (min. 94.4 V) to limit transient overvoltage. Its glass-passivated junction ensures stable leakage (<1.0 μA at VWM) and fast response time (<1.0 ps), critical for protecting sensitive downstream components from ESD and inductive switching spikes.

The device is rated for 400 W peak pulse power (10/1000 μs) up to 78 V and derates to 300 W above 78 V per Vishay's specification table; SMAJ85AHM3_A/H falls in the latter category. Its halogen-free, RoHS-compliant HM3 suffix confirms compliance with JESD201 Class 2 whisker resistance and MSL Level 1 reflow profile (peak 260 °C).

Key Specifications

Pinout & Package

Package: SMA (DO-214AC), surface-mount, single-ended unidirectional configuration with cathode band marking. Dimensions: 4.93 mm × 3.99 mm × 2.29 mm (L × W × H); matte tin-plated leads, solderable per J-STD-002 and JESD22-B102.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ85AHM3_A/H, SMAJ85AHE3_A/H offers identical clamping and thermal performance but omits halogen-free construction and whisker resistance, while SMAJ85A-M3/61 provides full equivalency in function and qualification-only differing in reel packaging code and delivery mode.

Availability

SMAJ85AHM3_A/H is available at Aetrix Electronics and suitable for automotive ECU design, industrial sensor interface hardening, and telecom power module development requiring stable component supply and AEC-Q101 assurance.

Supply support for SMAJ85AHM3_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, MOSFETs, optoelectronics, and passive components with emphasis on reliability and application-specific performance.

The SMAJ series is engineered for high-energy transient suppression in harsh environments, targeting automotive, industrial, and telecom applications where robustness, repeatable clamping, and long-term stability are mandatory.

FAQ

What is the maximum clamping voltage of SMAJ85AHM3_A/H under a 10/1000 μs surge?

The maximum clamping voltage (VC) of SMAJ85AHM3_A/H is 137 V at 2.2 A peak pulse current (IPPM), measured using the standardized 10/1000 μs double-exponential waveform. This value defines the upper voltage limit imposed on protected circuitry during transient events and is confirmed in Vishay's datasheet Table on page 2 under "ELECTRICAL CHARACTERISTICS" for the SMAJ85A variant. The SMAJ85AHM3_A/H shares identical electrical specs with the base SMAJ85A.

Is SMAJ85AHM3_A/H qualified for automotive use?

Yes, SMAJ85AHM3_A/H is AEC-Q101 qualified, as indicated by the "HM3" suffix per Vishay's ordering information table (page 3). This qualification covers stress tests including high-temperature reverse bias, temperature cycling, and ESD, confirming suitability for automotive powertrain, body electronics, and ADAS subsystems. The HM3 designation also certifies halogen-free and RoHS-compliant construction.

What does the "_A/H" suffix mean in SMAJ85AHM3_A/H?

The "_A/H" suffix in SMAJ85AHM3_A/H denotes the revision code ("A") and preferred package code ("H"), where "H" specifies 7-inch diameter plastic tape-and-reel packaging with 1800 units per reel. This coding aligns with Vishay's ordering convention shown in the "ORDERING INFORMATION" section (page 3), and does not affect electrical or thermal performance-only logistics and handling format.

Can SMAJ85AHM3_A/H be used in bidirectional applications?

No, SMAJ85AHM3_A/H is a unidirectional TVS diode, as confirmed by its part number ending in "A" (not "CA") and the presence of a cathode band marking. Bidirectional variants such as SMAJ85CA have symmetric breakdown in both polarities and no polarity marking. Using SMAJ85AHM3_A/H in bidirectional circuits would result in forward conduction during negative transients, potentially causing failure or incorrect clamping behavior.

What is the thermal resistance from junction to ambient for SMAJ85AHM3_A/H?

The typical thermal resistance from junction to ambient (RθJA) for SMAJ85AHM3_A/H is 120 °C/W, measured on a PCB with minimum recommended 0.2" × 0.2" (5.0 mm × 5.0 mm) copper pads per terminal, per Vishay's "THERMAL CHARACTERISTICS" table (page 3). This value guides heatsinking decisions and power derating calculations-especially critical when operating near the 3.3 W steady-state power dissipation limit at elevated ambient temperatures.