Taiwan Semiconductor Corporation SMAJ22CA

Overview

SMAJ22CA from Taiwan Semiconductor is a bidirectional surface-mount transient voltage suppressor (TVS) diode designed for robust overvoltage protection in DC power rails and signal lines. It features a 22 V working stand-off voltage (V_WM), 24.4–26.9 V breakdown voltage (V_BR), 35.5 V maximum clamping voltage (V_C) at 11.3 A peak pulse current, and 400 W peak pulse power rating with 10/1000 µs waveform - deployed in automotive infotainment power supplies and industrial I/O interfaces.

For engineers reviewing the SMAJ22CA datasheet, SMAJ22CA pinout, SMAJ22CA application, or SMAJ22CA equivalent, key selection criteria include bidirectional clamping capability, DO-214AC package compatibility, ISO 7637-2 Pulse 1/2a/2b/3a/3b compliance, low leakage (<1 µA at 22 V), and junction temperature range of –55 °C to +150 °C.

Technical Context

The SMAJ22CA implements a glass-passivated silicon avalanche junction optimized for fast transient response (<1.0 ps from 0 V to V_{BR min}) and stable clamping under repetitive surge stress. Its bidirectional configuration enables symmetrical protection without polarity sensitivity, supporting both positive and negative transients on the same line.

It operates within a –55 °C to +150 °C junction temperature range and is rated for 40 A non-repetitive forward surge current (I_FSM, 8.3 ms half-sine). The device meets JESD201 Class 2 whisker resistance and UL 94V-0 flammability requirements, confirming suitability for high-reliability PCB assembly.

Key Specifications

Pinout & Package

DO-214AC (SMA) package: molded plastic case with matte tin-plated leads, cathode band marking polarity for unidirectional variants; SMAJ22CA is bidirectional and marked with "BX" code - no cathode band required. Weight: 0.060 g.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ22CA, SMBJ22CA offers higher surge capacity in a larger package, while P6SMB22CA provides equivalent clamping performance with extended supply chain reach - both require layout review due to DO-214AA vs. DO-214AC footprint differences.

Availability

SMAJ22CA is available at Aetrix Electronics and suitable for automotive infotainment systems, industrial programmable logic controllers, LED lighting drivers, and telecom DC power feeders requiring stable component supply across multi-year production cycles.

Supply support for SMAJ22CA 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

Taiwan Semiconductor Corporation (TSC) is a vertically integrated semiconductor manufacturer headquartered in Hsinchu, Taiwan, specializing in discrete power devices, TVS diodes, rectifiers, and MOSFETs since 1979.

The SMAJ series was developed specifically for AEC-Q101-compliant, surface-mount transient suppression in automotive and industrial environments - emphasizing reliability, fast response, and standardized DO-214AC packaging.

FAQ

What is the clamping voltage of SMAJ22CA at its rated peak pulse current?

The SMAJ22CA has a maximum clamping voltage (V_C) of 35.5 V when subjected to its rated peak pulse current of 11.3 A under the standard 10/1000 µs waveform. This value is measured per JEDEC test conditions and guarantees that downstream circuitry sees no more than 35.5 V during surge events - critical for protecting 3.3 V or 5 V logic interfaces powered from a 22 V rail. The SMAJ22CA maintains this clamping performance across its full operating temperature range.

Is SMAJ22CA unidirectional or bidirectional, and how is polarity indicated?

SMAJ22CA is a bidirectional TVS diode, meaning it provides symmetrical clamping for both positive- and negative-going transients without polarity dependence. Unlike unidirectional variants (e.g., SMAJ22A), SMAJ22CA does not feature a cathode band marking - its DO-214AC package uses "BX" as the marking code and requires no orientation during placement. This eliminates risk of reverse installation in high-speed automated assembly.

Does SMAJ22CA meet automotive transient immunity standards?

Yes, SMAJ22CA meets ISO 7637-2 requirements for Pulse 1 (inductive switch-off), Pulse 2a (battery line interruption), Pulse 2b (alternator load dump simulation), and Pulses 3a/3b (capacitive coupling and line impedance effects). Its 400 W peak pulse power rating and sub-1 µA leakage at 22 V make it suitable for front-end protection in automotive body control modules, infotainment systems, and ADAS sensor power supplies - though full AEC-Q101 qualification must be confirmed per lot documentation.

What is the thermal derating behavior of SMAJ22CA above 25°C ambient?

SMAJ22CA's peak pulse power rating derates linearly above 25°C ambient temperature, following the curve in Figure 2 of the Taiwan Semiconductor datasheet (U2102). At 85°C ambient, its 400 W rating reduces to approximately 280 W; at 125°C, it falls to ~160 W. This derating directly impacts surge survivability in enclosed, high-temperature environments - designers must validate clamping performance at worst-case operating temperature using the published derating graph.

Can SMAJ22CA replace SMAJ22A in an existing design?

No - SMAJ22CA and SMAJ22A are not interchangeable without layout and system validation. SMAJ22A is unidirectional (cathode-banded, marked "BW") with V_C = 39.4 V at 10.2 A, while SMAJ22CA is bidirectional (marked "BX") with lower V_C = 35.5 V at 11.3 A. Swapping them changes clamping symmetry, leakage profile, and surge current handling - potentially compromising protection in polarity-sensitive circuits or failing ISO 7637-2 Pulse 1 testing.