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

Taiwan Semiconductor Corporation SMAJ18C

Name: SMAJ18C
Brand: Taiwan Semiconductor Corporation
SKU: SMAJ18C
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SMAJ18C

Manufacturer:: Taiwan Semiconductor Corporation

Category:: TVS Diodes

Package:: DO-214AC, SMA

Datasheet:: SMAJ18C.pdf

Description:: 400W, 22.2V, 10%, BIDIRECTIONAL,

Quantity:: RFQ Add To RFQ list

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Inventory:3,927

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Product details

Overview

SMAJ18C from Taiwan Semiconductor is a unidirectional surface-mount transient voltage suppressor (TVS) diode in DO-214AC (SMA) package, designed for robust overvoltage protection in DC power rails. It features a 18 V working stand-off voltage (V_WM), 20.0–24.4 V breakdown voltage (V_BR), 32.2 V maximum clamping voltage (V_C) at 13.1 A peak pulse current, and 400 W peak pulse power rating with 10/1000 µs waveform - ideal for protecting SMPS outputs and DC/DC converter inputs against ESD and surge events.

For engineers reviewing the SMAJ18C datasheet, SMAJ18C pinout, SMAJ18C application, or SMAJ18C equivalent, key selection criteria include clamping performance under ISO 7637-2 Pulse 1/2a/2b/3a/3b, unidirectional polarity marking, DO-214AC thermal and mechanical compatibility, and leakage current ≤1 µA at 18 V - all critical for automotive and industrial power rail hardening.

Technical Context

The SMAJ18C operates as a unidirectional avalanche diode, triggered when reverse voltage exceeds its specified V_BR range (20.0–24.4 V at 1 mA test current). Its glass-passivated junction ensures stable breakdown characteristics and low leakage (<1 µA at V_WM = 18 V), while fast response time (<1.0 ps) enables effective suppression of ESD transients per IEC 61000-4-2.

It delivers 400 W peak pulse power (10/1000 µs) up to 25 °C, derating linearly above ambient temperature per Fig.2, and supports steady-state power dissipation of 1 W. The device meets JESD201 Class 2 whisker resistance and UL 94V-0 flammability requirements, confirming suitability for automated SMT assembly in high-reliability power systems.

Key Specifications

Parameter	Value and Actual Design Meaning
V_WM	18 V - Maximum continuous reverse operating voltage before conduction begins; sets safe margin below system rail voltage.
V_BR @ I_T=1 mA	20.0–24.4 V - Breakdown voltage range defining reliable turn-on threshold for transient clamping.
V_C @ I_PPM=13.1 A	32.2 V - Maximum clamped voltage during 10/1000 µs surge; determines protected circuit's peak stress level.
P_PPM	400 W - Peak pulse power handling capability with standard 10/1000 µs waveform; validates compliance with ISO 7637-2.
I_R @ V_WM	<1 µA - Reverse leakage at stand-off voltage; ensures minimal quiescent power loss and signal integrity in standby.
T_J Range	−55 to +150 °C - Operating junction temperature range; supports deployment in under-hood automotive and industrial environments.

Pinout & Package

DO-214AC (SMA) surface-mount package: molded epoxy case with matte tin-plated leads, cathode band marking polarity, 0.060 g typical weight, and UL 94V-0 rated compound. Designed for reflow soldering per J-STD-002.

Pin/Terminal	Circuit Role	Design Meaning
Anode	Forward conduction terminal	Connected to lower-potential side (e.g., ground or return path) in unidirectional configuration.
Cathode	Reverse-biased clamping terminal	Connected to protected line (e.g., 18 V rail); conducts during overvoltage to shunt energy to ground.

Key Features

Feature	Design Value
Glass-passivated junction	Ensures stable V_BR tolerance and long-term reliability under thermal cycling and humidity exposure.
Fast response time <1.0 ps	Enables effective suppression of sub-nanosecond ESD events before downstream ICs experience overstress.
ISO 7637-2 compliance (Pulse 1/2a/2b/3a/3b)	Validates robustness against automotive load dump, inductive switching, and battery disconnect transients.
Moisture sensitivity level 1 (J-STD-020)	Permits unlimited floor life and standard reflow without baking, reducing manufacturing overhead.

Applications

Automotive Power Rail Protection	Industrial SMPS Output Clamping
Use Scenario: Protecting 12 V/24 V battery-fed ECUs against load dump and alternator transients per ISO 7637-2 Pulse 5a/5b. IC Role / Device Role / Timing Role: Unidirectional TVS diode placed across input rail to clamp surges >32.2 V to ground. Use Value: Limits peak voltage seen by downstream DC/DC controllers and microcontrollers to ≤32.2 V during 400 W transient events.	Use Scenario: Safeguarding output stage of 18 V-output flyback converter against reflected switching spikes and coupling noise. IC Role / Device Role / Timing Role: Standoff-rated TVS connected between output and GND to absorb repetitive 10/1000 µs surges without degradation. Use Value: Maintains output regulation integrity by clamping transients before they disrupt feedback loop stability or damage rectifier diodes.
LED Driver Input Protection	On-Board DC/DC Converter Ingress Suppression
Use Scenario: Shielding constant-current LED driver ICs from hot-swap and cable discharge events in signage and street lighting. IC Role / Device Role / Timing Role: Unidirectional TVS on 18 V input bus, leveraging low 1 µA leakage to avoid affecting dimming accuracy. Use Value: Prevents latch-up or gate oxide damage in driver MOSFETs by limiting transient overshoot to 32.2 V with <1 ps reaction.	Use Scenario: Hardening 18 V input of point-of-load (POL) buck converters in telecom base station boards exposed to board-level ESD. IC Role / Device Role / Timing Role: Primary surge shunt element located adjacent to POL input capacitor to minimize inductance in clamping path. Use Value: Reduces voltage overshoot at converter input pins to within 32.2 V, preserving internal FET SOA and enabling reliable startup after surge.

Automotive Power Rail Protection

Industrial SMPS Output Clamping

Use Scenario: Protecting 12 V/24 V battery-fed ECUs against load dump and alternator transients per ISO 7637-2 Pulse 5a/5b.

IC Role / Device Role / Timing Role: Unidirectional TVS diode placed across input rail to clamp surges >32.2 V to ground.

Use Value: Limits peak voltage seen by downstream DC/DC controllers and microcontrollers to ≤32.2 V during 400 W transient events.

Use Scenario: Safeguarding output stage of 18 V-output flyback converter against reflected switching spikes and coupling noise.

IC Role / Device Role / Timing Role: Standoff-rated TVS connected between output and GND to absorb repetitive 10/1000 µs surges without degradation.

Use Value: Maintains output regulation integrity by clamping transients before they disrupt feedback loop stability or damage rectifier diodes.

LED Driver Input Protection

On-Board DC/DC Converter Ingress Suppression

Use Scenario: Shielding constant-current LED driver ICs from hot-swap and cable discharge events in signage and street lighting.

IC Role / Device Role / Timing Role: Unidirectional TVS on 18 V input bus, leveraging low 1 µA leakage to avoid affecting dimming accuracy.

Use Value: Prevents latch-up or gate oxide damage in driver MOSFETs by limiting transient overshoot to 32.2 V with <1 ps reaction.

Use Scenario: Hardening 18 V input of point-of-load (POL) buck converters in telecom base station boards exposed to board-level ESD.

IC Role / Device Role / Timing Role: Primary surge shunt element located adjacent to POL input capacitor to minimize inductance in clamping path.

Use Value: Reduces voltage overshoot at converter input pins to within 32.2 V, preserving internal FET SOA and enabling reliable startup after surge.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
SMAJ18A	Narrower V_BR range (20.0–22.1 V), lower V_C (29.2 V at 14.5 A), same package and P_PPM.	Better clamping ratio (V_C/V_BR ≈ 1.31 vs. 1.45), suited for tighter voltage margins.	Select SMAJ18A when lower clamping voltage is prioritized over wider V_BR tolerance.
SMBJ18C	Same V_WM/V_BR/V_C specs but in larger DO-214AA (SMB) package; higher thermal mass and 600 W P_PPM.	Higher surge endurance and improved thermal dissipation; requires PCB layout change.	Choose SMBJ18C for higher-reliability or higher-energy surge environments where DO-214AC footprint is not constrained.

Compared with SMAJ18C, SMAJ18A offers tighter clamping at the cost of reduced V_BR tolerance, while SMBJ18C provides greater surge robustness in a physically larger package - both require validation of layout and thermal interface, unlike the drop-in DO-214AC compatibility of SMAJ18C.

Availability

SMAJ18C is available at Aetrix Electronics and suitable for automotive power rail protection, industrial SMPS output clamping, and LED driver input protection requiring stable component supply, full traceability, and RoHS/halogen-free compliance.

Supply support for SMAJ18C 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 is engineered specifically for high-energy transient suppression in automotive, industrial, and consumer power systems - emphasizing ISO 7637-2 compliance, low leakage, and automated assembly readiness in compact DO-214AC packaging.

FAQ

What is the breakdown voltage range of the SMAJ18C?

The SMAJ18C has a minimum breakdown voltage (V_BR) of 20.0 V and a maximum of 24.4 V at 1 mA test current, as specified in the Taiwan Semiconductor datasheet. This range ensures consistent clamping behavior across production lots while accommodating thermal and process variation. The SMAJ18C must be selected with system voltage margins that respect this V_BR window to guarantee reliable turn-on during transients.

Is the SMAJ18C unidirectional or bidirectional?

The SMAJ18C is a unidirectional TVS diode, indicated by the "C" suffix and confirmed by its single cathode band marking and electrical specifications applying only in reverse bias. Unlike bidirectional variants (e.g., SMAJ18CA), the SMAJ18C does not conduct in forward direction beyond typical diode drop - making it appropriate for DC rail protection where polarity is fixed and reverse surge is the primary threat.

What is the maximum clamping voltage of the SMAJ18C under surge conditions?

The SMAJ18C exhibits a maximum clamping voltage (V_C) of 32.2 V at 13.1 A peak pulse current (I_PPM) with a 10/1000 µs waveform. This value defines the highest voltage imposed on the protected circuit during standardized surge testing and is critical for ensuring downstream components remain within their absolute maximum ratings. The SMAJ18C achieves this clamping performance while maintaining 400 W peak pulse power capability.

Does the SMAJ18C meet automotive transient immunity standards?

Yes, the SMAJ18C meets ISO 7637-2 requirements for Pulse 1 (inductive load disconnect), Pulse 2a (sudden load removal), Pulse 2b (supply line inductance), Pulse 3a (capacitive coupled noise), and Pulse 3b (ground noise), as explicitly stated in the Taiwan Semiconductor documentation. Its 400 W 10/1000 µs rating and verified clamping response make the SMAJ18C suitable for front-end protection in automotive ECUs, body control modules, and infotainment power supplies.

What is the moisture sensitivity level (MSL) of the SMAJ18C?

The SMAJ18C has a moisture sensitivity level (MSL) of Level 1 per J-STD-020, meaning it may be stored indefinitely at ambient conditions (≤30 °C / 60% RH) without baking prior to reflow soldering. This eliminates floor-life constraints and simplifies SMT line integration - a key advantage for high-volume manufacturing of industrial and automotive electronics where the SMAJ18C is deployed.

SMAJ18C 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:: -

Bidirectional Channels:: 1

Voltage - Reverse Standoff (Typ):: 18V

Voltage - Breakdown (Min):: 20V

Voltage - Clamping (Max) @ Ipp:: 32.2V

Current - Peak Pulse (10/1000µs):: 12.4A

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)

SMAJ18C FAQ

1.How can I place an order for SMAJ18C through Aetrix?

Please submit a Request for Quotation (RFQ) for SMAJ18C 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 SMAJ18C reliable?

The price and inventory of SMAJ18C are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMAJ18C is usually 5 days.

3.What payment methods are accepted for SMAJ18C?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMAJ18C transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for SMAJ18C?

SMAJ18C orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SMAJ18C 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 SMAJ18C?

For technical support, including SMAJ18C datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMAJ18C requirements.

6.How does Aetrix verify that SMAJ18C is sourced from the original manufacturer or authorized distributors?

All SMAJ18C 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 SMAJ18C meets industry standards.

7.What is the process for return or replacement of SMAJ18C?

All SMAJ18C units undergo pre-shipment inspection (PSI). If there is an issue with SMAJ18C, 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 SMAJ18C part is unused and in its original packaging.

Return procedure for SMAJ18C:

1.Submit a request within 90 days.

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

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