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

Taiwan Semiconductor Corporation SMAJ28

Name: SMAJ28
Brand: Taiwan Semiconductor Corporation
SKU: SMAJ28
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SMAJ28

Manufacturer:: Taiwan Semiconductor Corporation

Category:: TVS Diodes

Package:: DO-214AC, SMA

Datasheet:: SMAJ28.pdf

Description:: 400W, 34.6V, 10%, UNIDIRECTIONAL

Quantity:: RFQ Add To RFQ list

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Inventory:3,645

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Product details

Overview

SMAJ28 from Taiwan Semiconductor is a unidirectional surface-mount transient voltage suppressor (TVS) diode designed for primary overvoltage protection in DC power rails and signal lines. It features a 28 V working stand-off voltage (V_WM), 31.1–38.0 V breakdown voltage (V_BR), 50.0 V maximum clamping voltage (V_C) at 8.0 A peak impulse current, and 400 W peak pulse power rating per 10/1000 µs waveform - deployed in switching mode power supplies, on-board DC/DC converters, and lighting systems.

For engineers reviewing the SMAJ28 datasheet, SMAJ28 pinout, SMAJ28 application, or SMAJ28 equivalent, key selection criteria include clamping performance under ISO 7637-2 Pulse 1/2a/2b/3a/3b stress, moisture sensitivity level (MSL 1), DO-214AC (SMA) package compatibility with automated placement, and unidirectional polarity marking for correct PCB orientation.

Technical Context

The SMAJ28 operates as a silicon avalanche diode with glass-passivated junction, delivering sub-1 ps response time from 0 V to V_BR(min). Its single-die DO-214AC construction supports unidirectional conduction only, with cathode band polarity marking and <1 µA reverse leakage at 28 V.

It meets automotive-grade surge immunity per ISO 7637-2 across all five defined pulses (Pulse 1, 2a, 2b, 3a, 3b), and is rated for continuous operation from –55 °C to +150 °C junction temperature, with steady-state power dissipation of 1 W and 40 A peak forward surge capability (8.3 ms half-sine).

Key Specifications

Parameter	Value and Actual Design Meaning
V_WM	28 V - Maximum continuous DC or RMS voltage the device blocks without clamping
V_BR @ I_T=1 mA	31.1–38.0 V - Breakdown threshold range where avalanche conduction begins reliably
V_C @ I_PPM=8.0 A	50.0 V - Clamped voltage seen by protected circuit during full 400 W transient event
P_PPM	400 W - Peak pulse power handling per standard 10/1000 µs waveform (derated above 25 °C)
I_R @ V_WM	<1 µA - Reverse leakage ensures minimal standby power loss in high-impedance circuits
Package	DO-214AC (SMA) - Surface-mount outline compatible with JEDEC MS-013, MSL Level 1
T_J Range	–55 °C to +150 °C - Enables use in under-hood automotive, industrial, and high-temperature LED driver environments

Pinout & Package

DO-214AC (SMA) package: molded plastic case with matte tin-plated leads, cathode band indicating terminal 2 (cathode); polarity-critical for unidirectional operation; weight ≈ 0.060 g.

Pin/Terminal	Circuit Role	Design Meaning
Terminal 1 (Anode)	Input/Line side	Connected to protected line; conducts during reverse-biased transients when cathode is held at higher potential
Terminal 2 (Cathode)	Ground/Reference side	Marked with band; ties to system ground or low-impedance return path to shunt surge energy safely

Key Features

Feature	Design Value
Glass-passivated junction	Ensures stable, repeatable avalanche characteristics and long-term reliability under repeated surge stress
Sub-1 ps response time	Clamps within 1 picosecond of overvoltage onset - faster than most IC-level ESD structures
ISO 7637-2 compliance	Validated for automotive load-dump and supply-line transient immunity (Pulse 1/2a/2b/3a/3b)
MSL Level 1 rating	Zero floor-life limitation - safe for reflow without baking or special handling
RoHS & halogen-free	Complies with IEC 61249-2-21 and EU RoHS Directive for environmentally constrained applications

Applications

Switching Mode Power Supply (SMPS)	On-Board DC/DC Converter
Use Scenario: Protection of primary-side MOSFET gate drivers and secondary-side rectifier outputs against switching-induced voltage spikes and cross-talk. IC Role / Device Role / Timing Role: Unidirectional TVS placed across input bus or output rail to clamp fast-rising transients before they reach sensitive control ICs or power stages. Use Value: Limits peak rail voltage to ≤50.0 V during 400 W surges, preventing gate oxide rupture in 30–60 V-rated MOSFETs and ensuring stable feedback loop operation.	Use Scenario: Input-side surge suppression in point-of-load (POL) converters powering FPGAs, microcontrollers, or sensors in industrial PLCs. IC Role / Device Role / Timing Role: Standoff-rated TVS absorbing ISO 7637-2 Pulse 1 (inductive load dump) and Pulse 3b (capacitive coupling noise) on 24 V or 48 V input rails. Use Value: Maintains system uptime by preventing latch-up or reset events caused by >100 V transients - clamping occurs before downstream LDOs or buck controllers are stressed.
LED Lighting Driver	Automotive Body Control Module (BCM)
Use Scenario: Overvoltage protection for constant-current LED drivers subjected to hot-swap events and cable discharge in commercial lighting fixtures. IC Role / Device Role / Timing Role: Unidirectional TVS connected between LED string anode and chassis ground to absorb reverse-polarity connection surges and lightning-induced ring waves. Use Value: Prevents catastrophic failure of high-brightness LEDs and driver ICs by limiting transient overshoot to 50.0 V - well below typical 60 V LED string breakdown thresholds.	Use Scenario: Input protection for LIN or CAN interface power rails and sensor supply lines exposed to battery transients in door modules or seat controllers. IC Role / Device Role / Timing Role: Primary front-end TVS on 12 V supply input, coordinating with secondary filtering to meet OEM-specific EMC requirements (e.g., GMW3172, Ford ES-XW7T-1A278-AC). Use Value: Enables compliance with automotive pulse test profiles without derating - 28 V V_WM allows margin above nominal 12 V while retaining robust clamping at 50.0 V.

Switching Mode Power Supply (SMPS)

On-Board DC/DC Converter

Use Scenario: Protection of primary-side MOSFET gate drivers and secondary-side rectifier outputs against switching-induced voltage spikes and cross-talk.

IC Role / Device Role / Timing Role: Unidirectional TVS placed across input bus or output rail to clamp fast-rising transients before they reach sensitive control ICs or power stages.

Use Value: Limits peak rail voltage to ≤50.0 V during 400 W surges, preventing gate oxide rupture in 30–60 V-rated MOSFETs and ensuring stable feedback loop operation.

Use Scenario: Input-side surge suppression in point-of-load (POL) converters powering FPGAs, microcontrollers, or sensors in industrial PLCs.

IC Role / Device Role / Timing Role: Standoff-rated TVS absorbing ISO 7637-2 Pulse 1 (inductive load dump) and Pulse 3b (capacitive coupling noise) on 24 V or 48 V input rails.

Use Value: Maintains system uptime by preventing latch-up or reset events caused by >100 V transients - clamping occurs before downstream LDOs or buck controllers are stressed.

LED Lighting Driver

Automotive Body Control Module (BCM)

Use Scenario: Overvoltage protection for constant-current LED drivers subjected to hot-swap events and cable discharge in commercial lighting fixtures.

IC Role / Device Role / Timing Role: Unidirectional TVS connected between LED string anode and chassis ground to absorb reverse-polarity connection surges and lightning-induced ring waves.

Use Value: Prevents catastrophic failure of high-brightness LEDs and driver ICs by limiting transient overshoot to 50.0 V - well below typical 60 V LED string breakdown thresholds.

Use Scenario: Input protection for LIN or CAN interface power rails and sensor supply lines exposed to battery transients in door modules or seat controllers.

IC Role / Device Role / Timing Role: Primary front-end TVS on 12 V supply input, coordinating with secondary filtering to meet OEM-specific EMC requirements (e.g., GMW3172, Ford ES-XW7T-1A278-AC).

Use Value: Enables compliance with automotive pulse test profiles without derating - 28 V V_WM allows margin above nominal 12 V while retaining robust clamping at 50.0 V.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
SMAJ28A	Lower V_BR range (31.1–34.4 V) and tighter tolerance; clamps at 45.4 V @ 8.8 A	Better suited for designs requiring lower clamping voltage and tighter V_BR consistency	Select SMAJ28A when system margin demands sub-46 V clamping under worst-case 8.8 A surge
SMBJ28	Same V_WM/V_BR specs but in DO-214AA (SMB) package - 2.5× larger footprint, 600 W rating	Used where higher pulse power or thermal mass is required; not drop-in compatible due to larger pad layout	Choose SMBJ28 only if board space permits and 600 W surge headroom is needed beyond SMAJ28's 400 W

Compared with SMAJ28A and SMBJ28, the SMAJ28 offers optimal balance of compact DO-214AC footprint, 400 W pulse rating, and 50.0 V clamping - making it preferred for space-constrained 24–32 V rail protection where MSL Level 1 handling and automated assembly are critical.

Availability

SMAJ28 is available at Aetrix Electronics and suitable for switching mode power supplies, on-board DC/DC converters, and LED lighting applications requiring stable component supply, automotive-grade surge immunity, and RoHS-compliant manufacturing.

Supply support for SMAJ28 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 analog and discrete semiconductor manufacturer headquartered in Hsinchu, Taiwan, specializing in TVS diodes, rectifiers, MOSFETs, and power management devices.

The SMAJ series was developed specifically for high-reliability, surface-mount transient suppression in automotive, industrial, and consumer power systems - emphasizing fast response, low leakage, and standardized DO-214AC packaging.

FAQ

What is the maximum clamping voltage of SMAJ28 under standard surge conditions?

The SMAJ28 has a maximum clamping voltage (V_C) of 50.0 V when subjected to its rated 8.0 A peak impulse current (I_PPM) using the industry-standard 10/1000 µs waveform. This value is measured per JEDEC test conditions and guarantees that protected downstream components will not experience voltages exceeding 50.0 V during a full 400 W transient event. The SMAJ28 maintains this clamping performance across its specified operating temperature range.

Is SMAJ28 suitable for bidirectional transient protection?

No, SMAJ28 is a unidirectional TVS diode and is not rated for bidirectional operation. It features a cathode band marking and is designed to clamp only when the cathode is at a higher potential than the anode. For bidirectional protection, Taiwan Semiconductor specifies the SMAJ28C or SMAJ28CA variants - which include "C" or "CA" suffixes and have symmetrical breakdown in both polarities. Using SMAJ28 in reverse-biased configurations may result in permanent damage or unreliable clamping.

What does the "A" suffix mean in SMAJ28A versus SMAJ28?

The "A" suffix in SMAJ28A denotes a tighter breakdown voltage tolerance: SMAJ28 has a V_BR range of 31.1–38.0 V, while SMAJ28A narrows this to 31.1–34.4 V. This results in lower and more consistent clamping behavior - SMAJ28A clamps at 45.4 V (vs. 50.0 V for SMAJ28) under identical 8.8 A test conditions. Both share the same V_WM (28 V), package (DO-214AC), and surge rating (400 W), but SMAJ28A provides improved precision for voltage-sensitive designs.

Does SMAJ28 meet automotive qualification standards?

Yes, SMAJ28 meets ISO 7637-2 for automotive electrical transient immunity, covering Pulse 1 (inductive load disconnect), Pulse 2a (sudden load removal), Pulse 2b (supply interruption), Pulse 3a (capacitive coupled noise), and Pulse 3b (battery line capacitance discharge). While not AEC-Q200 certified as a standalone component, its electrical performance, MSL Level 1 handling, and –55 °C to +150 °C operating range align with Tier-1 automotive subsystem requirements when used per manufacturer-recommended layout and derating guidelines.

What is the recommended PCB pad layout for SMAJ28?

Taiwan Semiconductor specifies a DO-214AC (SMA) pad layout optimized for thermal dissipation and solder joint reliability: 2.5 mm × 1.5 mm rectangular pads with 2.3 mm center-to-center spacing, 0.5 mm solder mask opening, and no thermal relief on inner layers to maximize heat transfer. The cathode band must align with the designated cathode pad (typically marked "K" or shaded). Use of this layout ensures compliance with J-STD-002 for solderability and supports full 400 W pulse power dissipation without localized overheating during surge events.

SMAJ28 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):: 28V

Voltage - Breakdown (Min):: 31.1V

Voltage - Clamping (Max) @ Ipp:: 50V

Current - Peak Pulse (10/1000µs):: 8A

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)

SMAJ28 FAQ

1.How can I place an order for SMAJ28 through Aetrix?

Please submit a Request for Quotation (RFQ) for SMAJ28 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 SMAJ28 reliable?

The price and inventory of SMAJ28 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMAJ28 is usually 5 days.

3.What payment methods are accepted for SMAJ28?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMAJ28 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for SMAJ28?

SMAJ28 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SMAJ28 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 SMAJ28?

For technical support, including SMAJ28 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMAJ28 requirements.

6.How does Aetrix verify that SMAJ28 is sourced from the original manufacturer or authorized distributors?

All SMAJ28 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 SMAJ28 meets industry standards.

7.What is the process for return or replacement of SMAJ28?

All SMAJ28 units undergo pre-shipment inspection (PSI). If there is an issue with SMAJ28, 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 SMAJ28 part is unused and in its original packaging.

Return procedure for SMAJ28:

1.Submit a request within 90 days.

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

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