Taiwan Semiconductor Corporation SMAJ24AH

Overview

SMAJ24AH from Taiwan Semiconductor is a unidirectional surface-mount transient voltage suppressor (TVS) diode in DO-214AC (SMA) package, designed for automotive-grade overvoltage protection with 24 V working stand-off voltage, 26.7–29.5 V breakdown voltage at 1 mA test current, and 38.9 V maximum clamping voltage at 10.3 A peak impulse current under 10/1000 µs waveform. It delivers 400 W peak pulse power and meets ISO 7637-2 Pulse 1/2a/2b/3a/3b for vehicle electronics.

For engineers reviewing the SMAJ24AH datasheet, SMAJ24AH pinout, SMAJ24AH application, or SMAJ24AH equivalent, this device is selected for robust DC bus protection in automotive DC/DC converters, SMPS input stages, lighting control modules, and adapter surge immunity-where fast sub-1 ps response, AEC-Q101 qualification, and low leakage (<1 µA at 24 V) are critical.

Technical Context

The SMAJ24AH operates as a unidirectional avalanche diode with glass-passivated junction, enabling stable clamping during fast transients such as load dump or inductive switching events. Its 10/1000 µs waveform rating supports standardized automotive surge testing per ISO 7637-2, and its 150 °C max junction temperature ensures reliability in under-hood environments.

With a 24 V working stand-off voltage and 26.7–29.5 V breakdown range, it provides precise overvoltage thresholding while maintaining <1 µA reverse leakage above VWM. The DO-214AC package enables automated placement and complies with JESD201 Class 2 whisker resistance and UL 94V-0 flammability requirements.

Key Specifications

Pinout & Package

DO-214AC (SMA) package: molded plastic case with matte tin-plated leads, polarity indicated by cathode band on one end. Weight ≈ 0.060 g. Complies with J-STD-002 solderability and JESD201 Class 2 whisker resistance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ24AH, Littelfuse SMAJ24A offers identical electrical and mechanical specs with seamless drop-in compatibility, while ON Semiconductor SMAJ24AHE3/5BT trades 0.5 V higher clamping for comparable cost-making the former ideal for direct substitution and the latter suitable only after system-level transient margin validation.

Availability

SMAJ24AH is available at Aetrix Electronics and suitable for automotive electronics, industrial power supplies, LED lighting systems, and DC/DC converter designs requiring stable component supply with AEC-Q101 assurance and ISO 7637-2 compliance.

Supply support for SMAJ24AH 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 specializing in discrete power devices, TVS diodes, rectifiers, and MOSFETs, with global distribution and AEC-Q101-certified production lines.

The SMAJ series was developed specifically for automotive and industrial transient suppression, emphasizing fast response, high surge robustness, and process-controlled breakdown uniformity across voltage grades from 5.0 V to 188 V.

FAQ

What is the maximum clamping voltage of SMAJ24AH under standard 10/1000 µs surge conditions?

The SMAJ24AH has a maximum clamping voltage (VC) of 38.9 V when subjected to its rated peak impulse current of 10.3 A using the 10/1000 µs waveform. This value is measured per Figure 5 in the official Taiwan Semiconductor datasheet and defines the upper voltage limit imposed on protected circuitry during transient events. Designers use this parameter to verify that downstream components remain within their absolute maximum ratings during surge conditions.

Is SMAJ24AH unidirectional or bidirectional, and how is polarity identified?

SMAJ24AH is a unidirectional TVS diode, meaning it clamps only in reverse-bias mode and conducts forward current like a standard diode. Polarity is marked by a cathode band on the DO-214AC package body - the banded end connects to the protected line (e.g., 24 V rail), while the unbanded end connects to ground. This configuration ensures proper clamping action during positive transients on the supply line.

Does SMAJ24AH meet automotive qualification standards?

Yes, SMAJ24AH is AEC-Q101 qualified and explicitly tested to meet ISO 7637-2 Pulse 1, 2a, 2b, 3a, and 3b transient immunity requirements. Its construction includes glass-passivated junctions, JESD201 Class 2 whisker resistance, and moisture sensitivity level 1 (per J-STD-020), making it suitable for under-hood and body-control module applications where long-term reliability under thermal and mechanical stress is mandatory.

What is the reverse leakage current specification for SMAJ24AH at its working voltage?

At its rated working stand-off voltage (VWM) of 24 V and TA = 25 °C, the SMAJ24AH exhibits a maximum reverse leakage current (IR) of 1 µA. This ultra-low leakage ensures minimal standby power loss in always-on automotive systems such as telematics control units or gateway ECUs, and supports extended battery life in low-power keep-alive circuits.

Can SMAJ24AH be used in place of SMAJ24H, and what is the key performance difference?

Yes, SMAJ24AH can replace SMAJ24H in most applications, but with improved clamping performance: SMAJ24AH has a lower maximum clamping voltage (38.9 V vs. 43.0 V) and tighter breakdown voltage tolerance (26.7–29.5 V vs. 26.7–32.6 V). This results in better protection margin for sensitive 24 V logic and power ICs. The "A" suffix denotes enhanced VBR consistency and lower VC, confirmed in Taiwan Semiconductor's Electrical Specifications table on page 2 of the datasheet.