Vishay General Semiconductor - Diodes Division SMAJ20AHM3_A/H

Overview

SMAJ20AHM3_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 a 20 V stand-off voltage (VWM), 22.2–24.5 V breakdown voltage (VBR) at 1 mA, 32.4 V maximum clamping voltage (VC) at 12.3 A peak pulse current (IPPM), and 400 W peak pulse power (10/1000 μs waveform). It is used to protect MOSFETs, ICs, and sensor interfaces in automotive and industrial power supplies.

For engineers reviewing the SMAJ20AHM3_A/H datasheet, SMAJ20AHM3_A/H pinout, SMAJ20AHM3_A/H application, or SMAJ20AHM3_A/H equivalent, key selection criteria include clamping voltage margin vs. protected device's absolute maximum rating, thermal resistance (RθJA = 120 °C/W), AEC-Q101 qualification status, unidirectional polarity marking, and compatibility with automated SMT placement on 0.2" × 0.2" copper pads.

Technical Context

This TVS diode operates as a fast-acting shunt protector: under normal bias it presents high impedance (<1 μA leakage at 20 V), but triggers into low-impedance conduction when transient voltage exceeds its breakdown threshold. Its glass-passivated junction ensures stable VBR and low incremental surge resistance.

The device is rated for non-repetitive 10/1000 μs surges up to 400 W below 78 V (derated to 300 W above), with thermal performance defined by RθJA = 120 °C/W and RθJL = 30 °C/W. It meets MSL level 1 per J-STD-020 and supports peak forward surge current of 40 A (8.3 ms half-sine).

Key Specifications

Pinout & Package

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

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ20AHE3_A/H, SMAJ20AHM3_A/H adds halogen-free compliance without sacrificing clamping performance or thermal capability; versus SMAJ20A-E3/61, it retains identical protection characteristics while aligning with stricter material declarations required in automotive and telecom supply chains.

Availability

SMAJ20AHM3_A/H is available at Aetrix Electronics and suitable for automotive control units, industrial sensor nodes, and telecom power feeders requiring stable component supply with full AEC-Q101 traceability and halogen-free compliance.

Supply support for SMAJ20AHM3_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, efficiency, and application-specific validation.

The SMAJ series is engineered for robust transient suppression in harsh environments-designed to meet automotive, industrial, and telecom surge immunity standards while supporting high-volume SMT manufacturing.

FAQ

What is the clamping voltage of SMAJ20AHM3_A/H at its rated peak pulse current?

The SMAJ20AHM3_A/H has a maximum clamping voltage (VC) of 32.4 V when subjected to its rated peak pulse current (IPPM) of 12.3 A under the standard 10/1000 μs waveform. This value is measured per Figure 1 in Vishay document 88390 and defines the upper voltage limit imposed on the protected circuit during transient events. The SMAJ20AHM3_A/H maintains this clamping performance across its qualified operating temperature range.

Is SMAJ20AHM3_A/H qualified for automotive applications?

Yes, SMAJ20AHM3_A/H is AEC-Q101 qualified, as confirmed by Vishay's ordering code suffix "HM3" and documentation in revision 09-Jan-2024 of datasheet 88390. This qualification covers stress tests including HTGB, H3TRB, TC, and ESD per the AEC-Q101 standard, making SMAJ20AHM3_A/H suitable for under-hood and body-control module applications where reliability under thermal and mechanical stress is critical.

What does the "HM3" suffix indicate in SMAJ20AHM3_A/H?

The "HM3" suffix in SMAJ20AHM3_A/H denotes halogen-free, RoHS-compliant, and AEC-Q101 qualified construction. It distinguishes this variant from E3 (RoHS-compliant only) and HE3 (AEC-Q101 + RoHS) versions. The "H" prefix confirms halogen-free molding compound and plating, meeting IPC-1752A and EU Directive 2015/863 requirements-critical for automotive and telecom supply chain compliance.

How is polarity identified on SMAJ20AHM3_A/H?

SMAJ20AHM3_A/H is a unidirectional TVS diode, and polarity is marked by a visible cathode band on the SMA (DO-214AC) package body. The banded end corresponds to the cathode terminal, which must be connected to the line being protected (e.g., +20 V rail), while the anode connects to ground. No marking is present on bidirectional variants, but SMAJ20AHM3_A/H explicitly uses unidirectional configuration per its "A" suffix and datasheet Table 1.

What is the thermal resistance of SMAJ20AHM3_A/H, and how does it affect layout?

SMAJ20AHM3_A/H has a typical junction-to-ambient thermal resistance (RθJA) of 120 °C/W when mounted on the minimum recommended 0.2" × 0.2" (5.0 mm × 5.0 mm) copper pads per terminal, as specified in Vishay document 88390. To maintain TJ ≤ 150 °C under worst-case 400 W pulse conditions, PCB layout must adhere to this pad size and avoid excessive trace length or isolation; thermal vias beneath pads further improve heat dissipation in high-duty-cycle applications.