Send an Inquiry

To receive a quote for your project, please fill in the following information, and we’ll get back to you promptly.

Submit Inventory List

Please fill in the following information, and we’ll get back to you promptly.

Home > Products > Circuit Protection > Transient Voltage Suppressors (TVS) > TVS Diodes

Taiwan Semiconductor Corporation SMAJ12

Name: SMAJ12
Brand: Taiwan Semiconductor Corporation
SKU: SMAJ12
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

Compare

Part No.:: SMAJ12

Manufacturer:: Taiwan Semiconductor Corporation

Category:: TVS Diodes

Package:: DO-214AC, SMA

Datasheet:: SMAJ12.pdf

Description:: 400W, 14.8V, 10%, UNIDIRECTIONAL

Quantity:: RFQ Add To RFQ list

Payment:

Shipping:

Inventory:9,964

Please send an inquiry. Send us your inquiry, and we will respond immediately.

Product details

Overview

SMAJ12 from Taiwan Semiconductor is a unidirectional surface-mount transient voltage suppressor (TVS) diode designed for robust overvoltage protection in DC power lines and signal paths. It features a 12 V working stand-off voltage (V_WM), 13.3–16.3 V breakdown voltage (V_BR), 22.0 V maximum clamping voltage (V_C) at 18.2 A peak pulse current, and 400 W peak pulse power rating per 10/1000 µs waveform - deployed in switching mode power supplies, DC/DC converters, and lighting systems.

For engineers reviewing the SMAJ12 datasheet, SMAJ12 pinout, SMAJ12 application, or SMAJ12 equivalent, key selection criteria include its DO-214AC (SMA) package compatibility, unidirectional polarity marking, low leakage (<1 µA at 12 V), fast sub-1 ps response time, and ISO 7637-2 Pulse 1/2a/2b/3a/3b compliance for automotive-grade surge immunity.

Technical Context

The SMAJ12 operates as a unidirectional avalanche diode with glass-passivated junction, optimized for clamping transients before sensitive downstream circuitry. Its electrical behavior is defined by precise V_BR (13.3–16.3 V @ 1 mA), V_C ≤ 22.0 V @ I_PPM = 18.2 A, and thermal limits up to T_J = 150 °C.

It delivers 400 W peak pulse power under standard 10/1000 µs waveform conditions, derating linearly above 25 °C ambient per Fig.2, and supports bidirectional use only when paired with CA-suffix variants - SMAJ12 itself is strictly unidirectional with cathode band polarity marking.

Key Specifications

Parameter	Value and Actual Design Meaning
V_WM	12 V - Maximum continuous reverse operating voltage before significant leakage begins; sets system DC rail margin.
V_BR min/max	13.3 V / 16.3 V @ 1 mA - Confirmed avalanche onset range; ensures reliable triggering above nominal rail.
V_C @ I_PPM	22.0 V @ 18.2 A - Clamped voltage during worst-case 10/1000 µs surge; defines protected IC's voltage stress ceiling.
P_PPM	400 W - Peak pulse power handling per standard waveform; enables protection against high-energy transients like load dump.
I_R @ V_WM	<1 µA - Reverse leakage at 12 V; negligible power loss and no measurable impact on standby efficiency.
T_J max	150 °C - Maximum junction temperature; supports operation in enclosed industrial or automotive under-hood environments.
Package	DO-214AC (SMA) - Standard surface-mount outline with 0.060 g mass; compatible with automated pick-and-place and reflow profiles.

Pinout & Package

DO-214AC (SMA) package: molded epoxy case with matte tin-plated leads, cathode band marking polarity, and UL 94V-0 flammability rating. Weight ≈ 0.060 g. Meets JESD201 Class 2 whisker resistance and J-STD-020 Moisture Sensitivity Level 1.

Pin/Terminal	Circuit Role	Design Meaning
Anode	Forward conduction terminal	Connected to lower-potential side (e.g., GND or return path); conducts during forward surge events.
Cathode	Reverse-biased clamping terminal	Connected to protected line (e.g., +12 V rail); avalanches into conduction when V_IN exceeds V_BR.

Key Features

Feature	Design Value
Glass passivated junction	Ensures stable V_BR tolerance and long-term reliability under thermal cycling and humidity exposure.
Sub-1 ps response time	Clamps ESD and fast transients before propagation to downstream logic or analog circuitry.
ISO 7637-2 compliance	Validated for automotive Pulse 1 (inductive load disconnect), Pulse 2a/2b (switching transients), and Pulse 3a/3b (capacitive coupling).
RoHS & halogen-free	Meets IEC 61249-2-21 and EU RoHS Directive; suitable for environmentally regulated industrial and automotive production.

Applications

Switching Mode Power Supply (SMPS)	On-board DC/DC Converter
Use Scenario: Protection of primary-side controller ICs and secondary-side rectifiers against input line surges and transformer leakage spikes. IC Role / Device Role: Unidirectional TVS placed across input bulk capacitor or output rail to clamp overshoot. Use Value: Limits transient voltage to ≤22.0 V, preventing gate oxide rupture in MOSFET drivers and overvoltage shutdown in PWM controllers.	Use Scenario: Safeguarding point-of-load (POL) regulators in telecom base stations and server motherboards from board-level coupling noise. IC Role / Device Role: Rail-to-rail clamping device on 12 V or 5 V distribution net, adjacent to regulator input. Use Value: Withstands 18.2 A peak impulse without degradation, preserving regulation integrity during hot-swap or load-step events.
Lighting Application	Automotive Body Control Module (BCM)
Use Scenario: Overvoltage suppression in LED driver circuits exposed to inductive kickback from relay-controlled ballasts or dimming FETs. IC Role / Device Role: Parallel-connected TVS across LED string or driver IC supply pins. Use Value: 400 W pulse rating absorbs energy from 100 mJ+ transients typical in 24 V commercial lighting systems.	Use Scenario: Input protection for microcontroller I/O and CAN transceiver power rails subjected to battery load dump and jump-start pulses. IC Role / Device Role: Primary front-end clamp on 12 V supply rail entering BCM housing. Use Value: Certified to ISO 7637-2 Pulse 1 (−150 V, 50 ms) and Pulse 2b (−100 V, 100 ms), enabling direct integration without external filtering.

Switching Mode Power Supply (SMPS)

On-board DC/DC Converter

Use Scenario: Protection of primary-side controller ICs and secondary-side rectifiers against input line surges and transformer leakage spikes.

IC Role / Device Role: Unidirectional TVS placed across input bulk capacitor or output rail to clamp overshoot.

Use Value: Limits transient voltage to ≤22.0 V, preventing gate oxide rupture in MOSFET drivers and overvoltage shutdown in PWM controllers.

Use Scenario: Safeguarding point-of-load (POL) regulators in telecom base stations and server motherboards from board-level coupling noise.

IC Role / Device Role: Rail-to-rail clamping device on 12 V or 5 V distribution net, adjacent to regulator input.

Use Value: Withstands 18.2 A peak impulse without degradation, preserving regulation integrity during hot-swap or load-step events.

Lighting Application

Automotive Body Control Module (BCM)

Use Scenario: Overvoltage suppression in LED driver circuits exposed to inductive kickback from relay-controlled ballasts or dimming FETs.

IC Role / Device Role: Parallel-connected TVS across LED string or driver IC supply pins.

Use Value: 400 W pulse rating absorbs energy from 100 mJ+ transients typical in 24 V commercial lighting systems.

Use Scenario: Input protection for microcontroller I/O and CAN transceiver power rails subjected to battery load dump and jump-start pulses.

IC Role / Device Role: Primary front-end clamp on 12 V supply rail entering BCM housing.

Use Value: Certified to ISO 7637-2 Pulse 1 (−150 V, 50 ms) and Pulse 2b (−100 V, 100 ms), enabling direct integration without external filtering.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
SMAJ12A	Narrower V_BR range (13.3–14.7 V vs. 13.3–16.3 V); tighter 5% tolerance; same V_C (19.9 V) and I_PPM (20.1 A).	Better suited for precision-clamp designs where consistent turn-on threshold is critical; identical footprint and polarity.	Select SMAJ12A when V_BR consistency across production lots is required; SMAJ12 offers broader tolerance for cost-sensitive volume applications.
SMBJ12	Same V_WM/V_BR/V_C specs but in DO-214AA (SMB) package - 2.54 mm lead spacing vs. SMA's 2.29 mm; 600 W P_PPM rating.	Higher power handling supports longer surge durations; larger footprint may require PCB redesign.	Choose SMBJ12 only if system-level testing confirms need for >400 W clamping; otherwise SMAJ12 provides optimal size-power balance in space-constrained layouts.

Compared with SMAJ12A, the SMAJ12 offers wider V_BR tolerance at lower cost, while SMBJ12 trades smaller footprint for higher pulse power - making SMAJ12 the preferred choice for compact, cost-optimized 12 V rail protection where 400 W suffices and ±10% V_BR variation is acceptable.

Availability

SMAJ12 is available at Aetrix Electronics and suitable for switching mode power supplies, on-board DC/DC converters, and lighting applications requiring stable component supply, full traceability, and lifecycle continuity.

Supply support for SMAJ12 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 for industrial, computing, and automotive markets.

The SMAJ series was developed specifically for surface-mount surge protection in high-reliability DC power systems, emphasizing fast response, low clamping, and automotive-grade transient immunity.

FAQ

What is the maximum clamping voltage of the SMAJ12 under standard test conditions?

The SMAJ12 has a maximum clamping voltage (V_C) of 22.0 V when subjected to its rated peak pulse current of 18.2 A using the 10/1000 µs waveform. This value is guaranteed across the full operating temperature range and represents the highest voltage the device allows to appear across protected circuitry during a surge event - a critical parameter for ensuring downstream ICs remain within absolute maximum ratings.

Is the SMAJ12 suitable for automotive applications requiring ISO 7637-2 compliance?

Yes, the SMAJ12 meets ISO 7637-2 requirements for Pulse 1, 2a, 2b, 3a, and 3b, as confirmed in Taiwan Semiconductor's official documentation. Its 400 W peak pulse power rating, low clamping voltage, and specified response time make it appropriate for protecting ECUs, body control modules, and infotainment power rails against conducted transients encountered in 12 V vehicle electrical systems.

What is the polarity configuration of the SMAJ12, and how is it marked on the device?

The SMAJ12 is a unidirectional TVS diode with cathode band marking on the DO-214AC (SMA) package body. The banded end corresponds to the cathode terminal and must be connected toward the higher-potential side (e.g., +12 V rail), while the anode connects to ground or return. This polarity is essential for correct clamping operation and is clearly indicated in the manufacturer's marking diagram and mechanical drawings.

How does the SMAJ12 differ from the SMAJ12A variant?

The SMAJ12A features a tighter breakdown voltage tolerance (13.3–14.7 V vs. 13.3–16.3 V for SMAJ12) and a slightly lower clamping voltage of 19.9 V at 20.1 A, whereas SMAJ12 clamps at 22.0 V at 18.2 A. Both share identical package, polarity, and environmental ratings. The SMAJ12A is intended for designs requiring tighter V_BR control, while SMAJ12 offers broader tolerance for cost-sensitive applications where exact turn-on voltage is less critical.

What is the maximum steady-state power dissipation rating for the SMAJ12?

The SMAJ12 has a steady-state power dissipation (P_D) rating of 1 W at 25 °C ambient temperature. This value applies to continuous DC or low-frequency reverse-bias conditions and must be derated linearly above 25 °C per the thermal resistance curve in the datasheet. It is distinct from the 400 W peak pulse rating, which applies only to short-duration transient events.

SMAJ12 Specifications

Product attributes: Attribute value

Manufacturer:: Taiwan Semiconductor Corporation

Package/Case:: DO-214AC, SMA

Series:: SMAJ

Packaging:: Tape & Reel (TR)

Product Status:: Active

Type:: Zener

Unidirectional Channels:: 1

Bidirectional Channels:: -

Voltage - Reverse Standoff (Typ):: 12V

Voltage - Breakdown (Min):: 13.3V

Voltage - Clamping (Max) @ Ipp:: 22V

Current - Peak Pulse (10/1000µs):: 18.2A

Power - Peak Pulse:: 400W

Power Line Protection:: No

Applications:: General Purpose

Capacitance @ Frequency:: -

Operating Temperature:: -55°C ~ 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: DO-214AC (SMA)

SMAJ12 FAQ

1.How can I place an order for SMAJ12 through Aetrix?

Please submit a Request for Quotation (RFQ) for SMAJ12 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for SMAJ12 reliable?

The price and inventory of SMAJ12 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMAJ12 is usually 5 days.

3.What payment methods are accepted for SMAJ12?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMAJ12 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for SMAJ12?

SMAJ12 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SMAJ12 order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for SMAJ12?

For technical support, including SMAJ12 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMAJ12 requirements.

6.How does Aetrix verify that SMAJ12 is sourced from the original manufacturer or authorized distributors?

All SMAJ12 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that SMAJ12 meets industry standards.

7.What is the process for return or replacement of SMAJ12?

All SMAJ12 units undergo pre-shipment inspection (PSI). If there is an issue with SMAJ12, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The SMAJ12 part is unused and in its original packaging.

Return procedure for SMAJ12:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

Tech Hub

2026-09-11 Comparator Circuit: Voltage Thresholds, Op-Amp Differences, LM393 and Practical Design

Comparator circuit design covering voltage thresholds, input limits, open-collector outputs, LM393 wiring, op-amp differences, hysteresis, timing, window detection and practical fault diagnosis.

2026-09-10 Schmitt Trigger Explained: Hysteresis, Circuits, Inverters and Applications

Schmitt triggers use separate rising and falling thresholds to stabilize slow or noisy signals. This guide covers hysteresis, 74HC14 and 74HCT14 selection, comparator calculations, RC oscillators and p…

2026-09-09 Counterfeit Electronic Components: How to Detect, Authenticate, and Test Suspect Parts

Counterfeit components can hide behind convincing markings and passing basic function tests. This engineering reference covers source traceability, external inspection, X-ray, XRF, electrical testing, …

2026-09-08 Obsolete Electronic Components: How to Source and Evaluate Replacements

A practical engineering and sourcing framework covering lifecycle verification, lifetime-buy calculations, replacement qualification, supplier checks and counterfeit-risk controls.

2026-09-07 TTL vs CMOS Logic Levels: 74HC and 74HCT Compatibility Explained

TTL and CMOS logic families differ in thresholds, loading, output drive, power and timing. This engineering guide compares 74HC and 74HCT, calculates noise margins and checks 3.3 V/5 V compatibility.

2026-09-04 Logic Level Shifter: How to Connect 3.3V and 5V Logic Safely

A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.

2026-09-03 74HC595 vs TPIC6B595: Output Drive, Pinout, Current, and Load Selection

The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…

2026-09-02 74HC595 Pinout, Timing, Output Current, and Applications

The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…

2026-09-01 Latch vs Flip-Flop: Timing, Differences and Design Choices

A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…

2026-08-30 D Latch Circuit: Truth Table, Timing, ICs and Applications

A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …