Vishay General Semiconductor - Diodes Division SMCJ78AHM3_A/H

Overview

SMCJ78AHM3_A/H from Vishay General Semiconductor is a unidirectional surface-mount Transient Voltage Suppressor (TVS) diode in SMC (DO-214AB) package, designed for high-energy surge protection with 78 V standoff voltage, 126 V clamping voltage at 11.9 A peak pulse current, and 1500 W peak pulse power rating. It protects MOSFETs, ICs, and sensor signal lines against inductive switching transients and lightning-induced surges in automotive and industrial power electronics.

For engineers reviewing the SMCJ78AHM3_A/H datasheet, SMCJ78AHM3_A/H pinout, SMCJ78AHM3_A/H application, or SMCJ78AHM3_A/H equivalent, key selection criteria include its AEC-Q101 qualification, halogen-free RoHS-compliant construction, 1500 W 10/1000 μs surge capability, and compatibility with automated SMT placement on standard PCB pad layouts.

Technical Context

This TVS diode operates as a clamping device that remains non-conductive below 78 V reverse standoff voltage (VWM), then rapidly transitions to low-impedance conduction when transient voltage exceeds its 86.7–95.8 V breakdown range (VBR at 1 mA). Its glass-passivated junction ensures stable leakage performance and fast response time under ESD and surge events.

Thermal design relies on its 75 °C/W junction-to-ambient thermal resistance (RθJA) and 15 °C/W junction-to-lead (RθJL), requiring minimum 8.0 mm × 8.0 mm copper pads per terminal for full 1500 W rating. The device is rated for -55 °C to +150 °C operating junction temperature and meets J-STD-020 MSL Level 1 reflow profile (260 °C peak).

Key Specifications

Pinout & Package

SMCJ78AHM3_A/H uses the SMC (DO-214AB) package: a rectangular, molded plastic case with two coplanar matte tin-plated leads. Polarity is marked by a cathode band on the body; the banded end is the cathode (K), and the opposite end is the anode (A). Leads are solderable per J-STD-002 and JESD 22-B102.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMCJ78AHM3_A/H, SMAJ78AHE3_A/H offers reduced surge capacity in a smaller footprint, while SMCJ78AHE3_A/H matches mechanical and electrical performance but lacks halogen-free compliance-making SMCJ78AHM3_A/H the sole option meeting both AEC-Q101 and halogen-free mandates for automotive designs.

Availability

SMCJ78AHM3_A/H is available at Aetrix Electronics and suitable for automotive power distribution, industrial motor drive control, telecom power interface, and consumer appliance mainboard applications requiring stable component supply and long-term lifecycle support.

Supply support for SMCJ78AHM3_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, TVS devices, and optoelectronics with emphasis on reliability, precision, and application-specific optimization.

The SMCJ series is engineered for high-power transient suppression in harsh environments, targeting automotive, industrial, and telecom systems where robust 1500 W surge immunity and AEC-Q101 validation are mandatory.

FAQ

What is the clamping voltage of SMCJ78AHM3_A/H at its rated peak pulse current?

The SMCJ78AHM3_A/H has a maximum clamping voltage (VC) of 126 V when subjected to its rated peak pulse current (IPPM) of 11.9 A under the standard 10/1000 μs waveform. This value is measured per ANSI/IEEE C62.35 and confirmed in Vishay's Document Number 88394, ensuring predictable voltage limiting during surge events. The 126 V clamping level directly defines the maximum stress imposed on downstream components protected by the SMCJ78AHM3_A/H.

Is SMCJ78AHM3_A/H qualified for automotive applications?

Yes, SMCJ78AHM3_A/H is AEC-Q101 qualified, as indicated by the "HM3" suffix and confirmed in Vishay's ordering information table and mechanical data section. This qualification covers stress tests including temperature cycling, high-temperature reverse bias, and surge endurance-making SMCJ78AHM3_A/H suitable for under-hood and chassis-mounted automotive electronics where reliability under thermal and electrical stress is critical.

What does the "HM3" suffix signify in SMCJ78AHM3_A/H?

"HM3" denotes halogen-free, RoHS-compliant, and AEC-Q101 qualified construction per Vishay's material categorization system. It distinguishes SMCJ78AHM3_A/H from non-halogen-free variants like SMCJ78AHE3_A/H and confirms compliance with IEC 61249-2-21 and automotive reliability standards. The "_A/H" further specifies packaging: 7-inch tape-and-reel with 850 units per reel, optimized for SMT placement.

How does the thermal performance of SMCJ78AHM3_A/H affect PCB layout?

SMCJ78AHM3_A/H requires minimum 8.0 mm × 8.0 mm copper pads per terminal to achieve its full 1500 W rating, as specified in Vishay's derating curves and thermal characteristics table. Its RθJA of 75 °C/W assumes this pad area; smaller pads increase junction temperature, reducing surge capability and lifetime. Layout must also avoid thermal isolation-ground planes and internal copper layers should connect directly to the pads to support heat dissipation during repetitive surges.

Can SMCJ78AHM3_A/H be used in bidirectional configurations?

No, SMCJ78AHM3_A/H is a unidirectional TVS diode, as confirmed by its part number suffix "A" (not "CA") and polarity marking (cathode band). Bidirectional operation requires the "CA" variant (e.g., SMCJ78CA), which has symmetrical breakdown in both directions. Using SMCJ78AHM3_A/H in reverse-biased AC applications would result in forward conduction and potential failure; always verify polarity alignment in circuit design.