Vishay General Semiconductor - Diodes Division SMBJ20CAHM3_B/I

Overview

SMBJ20CAHM3_B/I from Vishay General Semiconductor is a bidirectional surface-mount Transient Voltage Suppressor (TVS) diode in the SMB (DO-214AA) package, designed for clamping voltage transients on signal or power lines. It features a 20 V stand-off voltage (V_WM), 22.2–24.5 V breakdown voltage (V_BR) at 1 mA, 32.4 V maximum clamping voltage (V_C) at 18.5 A peak pulse current, and 600 W peak pulse power capability with a 10/1000 µs waveform - used to protect MOSFETs, ICs, and sensor interfaces in industrial and telecom equipment.

For engineers reviewing the SMBJ20CAHM3_B/I datasheet, SMBJ20CAHM3_B/I pinout, SMBJ20CAHM3_B/I application, or SMBJ20CAHM3_B/I equivalent, this device is selected for robust ESD and surge protection where bidirectional clamping, low leakage (<1 µA at V_WM), AEC-Q101 qualification, halogen-free RoHS compliance, and MSL Level 1 reflow compatibility are required.

Technical Context

This bidirectional TVS operates symmetrically across both polarities, delivering identical clamping performance regardless of transient polarity. Its glass-passivated junction ensures stable V_BR tolerance (±5%), fast response time (<1.0 ps), and low incremental surge resistance - critical for protecting sensitive inputs against lightning-induced surges and inductive switching spikes.

The device is rated for continuous operation from –55 °C to +150 °C junction temperature, with thermal resistance R_θJA = 100 °C/W (on standard 0.2" × 0.2" copper pads) and R_θJL = 20 °C/W. Its 1.0 µA max reverse leakage at 20 V supports low-power sensor line protection without signal degradation.

Key Specifications

Pinout & Package

Package: SMB (DO-214AA), surface-mount, halogen-free, RoHS-compliant, MSL Level 1 (260 °C peak reflow). Dimensions: 4.57 mm × 3.94 mm × 2.20 mm (L × W × H); cathode band omitted (bidirectional type).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMBJ20CAHE3_B/I, the SMBJ20CAHM3_B/I adds halogen-free compliance and AEC-Q101 qualification without trade-offs in clamping or power rating; versus SMAJ20CAHM3_A/I, it delivers 50 % higher surge power and superior thermal dissipation in the larger SMB package.

Availability

SMBJ20CAHM3_B/I is available at Aetrix Electronics and suitable for industrial motor drives, automotive body control modules, telecom power feeds, and consumer sensor interfaces requiring stable component supply, long-lifecycle assurance, and traceable halogen-free sourcing.

Supply support for SMBJ20CAHM3_B/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, rectifiers, MOSFETs, and protection devices with emphasis on reliability, efficiency, and application-specific optimization.

The SMBJ series was engineered for high-energy transient suppression in harsh environments - targeting automotive, industrial, and telecom systems where failure due to voltage surges must be eliminated.

FAQ

What is the clamping voltage of SMBJ20CAHM3_B/I at its rated peak pulse current?

The SMBJ20CAHM3_B/I has a maximum clamping voltage (V_C) of 32.4 V at its rated peak pulse current (I_PPM) of 18.5 A, measured under the standardized 10/1000 µs double-exponential surge waveform. This value ensures downstream components see no more than 32.4 V during worst-case transients, making SMBJ20CAHM3_B/I suitable for protecting 24 V systems with 3.3 V or 5 V interface ICs.

Is SMBJ20CAHM3_B/I suitable for automotive applications?

Yes - SMBJ20CAHM3_B/I is AEC-Q101 qualified and manufactured with halogen-free, RoHS-compliant materials. Its –55 °C to +150 °C operating junction temperature range, MSL Level 1 reflow rating, and validated surge endurance meet requirements for body electronics, infotainment power supplies, and LIN/CAN node protection. The "HM3" suffix explicitly denotes AEC-Q101 + halogen-free compliance.

How does the bidirectional design of SMBJ20CAHM3_B/I affect its placement on the PCB?

The SMBJ20CAHM3_B/I has no polarity marking and functions identically in either orientation, simplifying layout and assembly. Unlike unidirectional TVS diodes, it requires no alignment to anode/cathode - enabling direct placement across differential pairs (e.g., RS-485 A/B), AC signal lines, or floating power rails without risk of reverse installation. This eliminates orientation-related assembly errors and reduces test coverage complexity.

What is the maximum reverse leakage current for SMBJ20CAHM3_B/I at its stand-off voltage?

At its 20 V stand-off voltage (V_WM), the SMBJ20CAHM3_B/I exhibits a maximum reverse leakage current (I_D) of 1.0 µA at 25 °C. This ultra-low leakage preserves signal integrity on high-impedance nodes such as sensor outputs, battery-monitoring dividers, and I²C pull-up networks - critical for low-power and precision analog designs where even nanoamp-level currents impact accuracy.

Can SMBJ20CAHM3_B/I replace SMBJ20A in an existing design?

No - SMBJ20A is unidirectional, while SMBJ20CAHM3_B/I is bidirectional. Replacing SMBJ20A with SMBJ20CAHM3_B/I on a DC line with defined polarity may result in unintended conduction during normal operation if the circuit relies on forward-biased blocking behavior. For bidirectional signal lines (e.g., USB, RS-485), SMBJ20CAHM3_B/I is appropriate; for unidirectional DC rails, use SMBJ20AHM3_B/I instead.