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

Taiwan Semiconductor Corporation SMAJ170

Name: SMAJ170
Brand: Taiwan Semiconductor Corporation
SKU: SMAJ170
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SMAJ170

Manufacturer:: Taiwan Semiconductor Corporation

Category:: TVS Diodes

Package:: DO-214AC, SMA

Datasheet:: SMAJ170.pdf

Description:: 300W, 210V, 10%, UNIDIRECTIONAL,

Quantity:: RFQ Add To RFQ list

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Inventory:2,171

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Product details

Overview

SMAJ170 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 170 V working stand-off voltage (V_WM), 189–231 V breakdown voltage (V_BR @ 1 mA), 304 V maximum clamping voltage (V_C @ 1 A), 400 W peak pulse power (10/1000 µs), and <1 µA reverse leakage at V_WM, making it suitable for automotive and industrial DC/DC converter input protection.

For engineers reviewing the SMAJ170 datasheet, SMAJ170 pinout, SMAJ170 application, or SMAJ170 equivalent, key selection criteria include clamping performance under ISO 7637-2 Pulse 1/2a/2b/3a/3b transients, thermal derating above 25°C, unidirectional polarity marking, and compatibility with automated SMT placement on high-reliability power supply boards.

Technical Context

The SMAJ170 operates as a silicon avalanche diode that remains non-conductive below V_WM = 170 V and rapidly clamps transient energy above V_BR (min 189 V) with sub-nanosecond response. Its glass-passivated junction ensures stable breakdown characteristics and low leakage (<1 µA at V_WM).

It delivers 400 W peak pulse power per 10/1000 µs waveform up to T_A = 25°C, derating linearly above that 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 for its molding compound.

Key Specifications

Parameter	Value and Actual Design Meaning
V_WM	170 V - Maximum continuous DC or RMS voltage the device blocks without conduction
V_BR @ I_T=1 mA	189–231 V - Breakdown threshold range where avalanche conduction begins reliably
V_C @ I_PPM=1 A	304 V - Maximum clamped voltage during 1 A 10/1000 µs surge, limiting downstream stress
P_PPM	400 W - Peak transient power handling capability at 25°C ambient, critical for ISO 7637-2 compliance
I_R @ V_WM	<1 µA - Ultra-low reverse leakage preserves efficiency in high-impedance bias networks
T_J Range	−55°C to +150°C - Extended junction temperature rating enables under-hood and industrial deployment
Package	DO-214AC (SMA) - Standardized surface-mount outline with cathode band polarity marking

Pinout & Package

DO-214AC (SMA) package: molded plastic case with matte tin-plated leads, cathode indicated by a band on the body; polarity-critical for unidirectional operation; weight ≈ 0.060 g.

Pin/Terminal	Circuit Role	Design Meaning
Anode	Low-side reference node	Connected to ground or low-voltage rail; defines current path during clamping
Cathode	Protected line input	Connected to the line being protected (e.g., +170 V rail); conducts avalanche current to anode 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
Fast response time <1.0 ps	Clamps ESD and fast transients before sensitive downstream circuitry is damaged
ISO 7637-2 compliant	Validated for automotive load dump and switching transient immunity (Pulse 1/2a/2b/3a/3b)
Moisture sensitivity level 1	Enables standard SMT reflow without baking or special handling per J-STD-020
RoHS & halogen-free	Meets IEC 61249-2-21 and environmental compliance for global electronics manufacturing

Applications

Automotive Power Input Protection	Industrial DC/DC Converter Input
Use Scenario: Protecting 24 V and 48 V battery-fed ECUs against load dump and alternator transients. IC Role / Device Role / Timing Role: Unidirectional TVS placed between battery rail and DC/DC input, clamping surges >170 V to ≤304 V. Use Value: Enables compliance with ISO 7637-2 Pulse 5a (load dump) without additional filtering or derating margin.	Use Scenario: Safeguarding isolated DC/DC modules in programmable logic controllers (PLCs) and motor drives. IC Role / Device Role / Timing Role: Primary overvoltage clamp on primary-side input, absorbing repetitive switching spikes from inductive loads. Use Value: Maintains system uptime by preventing MOSFET gate oxide failure and controller latch-up during field-induced transients.
Telecom Power Adapter Interface	LED Driver Front-End Protection
Use Scenario: Input-stage surge suppression in AC/DC adapters powering base station radios and remote PHY units. IC Role / Device Role / Timing Role: Standoff-rated TVS across bulk capacitor input, triggered only during line surges exceeding 170 V. Use Value: Eliminates need for secondary crowbar circuits while meeting IEC 61000-4-5 Level 3 (2 kV) with minimal board space.	Use Scenario: Overvoltage guard for constant-current LED drivers in streetlight and stadium lighting systems. IC Role / Device Role / Timing Role: Unidirectional clamp on high-side switch node, protecting driver ICs from inductive kickback during PWM dimming. Use Value: Extends driver lifetime by limiting transient voltage stress to <304 V, well below typical 350 V MOSFET drain ratings.

Automotive Power Input Protection

Industrial DC/DC Converter Input

Use Scenario: Protecting 24 V and 48 V battery-fed ECUs against load dump and alternator transients.

IC Role / Device Role / Timing Role: Unidirectional TVS placed between battery rail and DC/DC input, clamping surges >170 V to ≤304 V.

Use Value: Enables compliance with ISO 7637-2 Pulse 5a (load dump) without additional filtering or derating margin.

Use Scenario: Safeguarding isolated DC/DC modules in programmable logic controllers (PLCs) and motor drives.

IC Role / Device Role / Timing Role: Primary overvoltage clamp on primary-side input, absorbing repetitive switching spikes from inductive loads.

Use Value: Maintains system uptime by preventing MOSFET gate oxide failure and controller latch-up during field-induced transients.

Telecom Power Adapter Interface

LED Driver Front-End Protection

Use Scenario: Input-stage surge suppression in AC/DC adapters powering base station radios and remote PHY units.

IC Role / Device Role / Timing Role: Standoff-rated TVS across bulk capacitor input, triggered only during line surges exceeding 170 V.

Use Value: Eliminates need for secondary crowbar circuits while meeting IEC 61000-4-5 Level 3 (2 kV) with minimal board space.

Use Scenario: Overvoltage guard for constant-current LED drivers in streetlight and stadium lighting systems.

IC Role / Device Role / Timing Role: Unidirectional clamp on high-side switch node, protecting driver ICs from inductive kickback during PWM dimming.

Use Value: Extends driver lifetime by limiting transient voltage stress to <304 V, well below typical 350 V MOSFET drain ratings.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
SMAJ170A	Narrower V_BR range (189–209 V vs. 189–231 V); tighter 5% tolerance; lower V_C = 275 V @ 1 A	Better suited for precision-clamp designs where lower clamping voltage is prioritized over wider V_BR tolerance	Select SMAJ170A when system-level transient testing shows margin exists below 275 V clamping
SMCJ170A	Same V_WM/V_BR specs but higher P_PPM = 1500 W (DO-214AB package); larger footprint and thermal mass	Used where higher single-pulse energy (e.g., ISO 7637-2 Pulse 5a) requires greater surge headroom	Choose SMCJ170A only if 400 W is insufficient per worst-case surge modeling; verify PCB layout change

Compared with SMAJ170A, the SMAJ170 offers broader V_BR tolerance and slightly higher clamping voltage, simplifying BOM consolidation across variable production lots; versus SMCJ170A, it trades peak power for smaller DO-214AC footprint and lower assembly cost-ideal for space-constrained 24–48 V industrial modules.

Availability

SMAJ170 is available at Aetrix Electronics and suitable for automotive power input protection, industrial DC/DC converter input stages, and telecom adapter interface circuits requiring stable component supply across extended temperature and surge environments.

Supply support for SMAJ170 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, serving global automotive, industrial, and consumer markets since 1979.

The SMAJ series is part of TSC's transient voltage suppression portfolio, engineered specifically for high-reliability, surface-mount overvoltage protection in harsh environments-including automotive subsystems and industrial power supplies-where fast response, low leakage, and ISO 7637-2 compliance are mandatory.

FAQ

What is the maximum clamping voltage of the SMAJ170 under a 10/1000 µs surge?

The SMAJ170 has a maximum clamping voltage (V_C) of 304 V when subjected to a 1 A peak impulse current with a 10/1000 µs waveform. This value is measured per the standard test condition defined in the datasheet and represents the upper limit of voltage seen by downstream circuitry during transient events. Designers must ensure that all protected components have voltage ratings exceeding 304 V to maintain functional safety. The SMAJ170 achieves this clamping performance while maintaining low leakage and fast response.

Is the SMAJ170 unidirectional or bidirectional, and how is polarity marked?

The SMAJ170 is a unidirectional TVS diode, intended for DC line protection where polarity is fixed. Polarity is marked by a cathode band on the DO-214AC (SMA) package body-this band identifies the cathode terminal, which must be connected to the line being protected (e.g., positive rail), while the anode connects to ground or return. Bidirectional variants use the "CA" suffix (e.g., SMAJ170CA); the SMAJ170 does not support symmetrical clamping in both directions.

Does the SMAJ170 meet automotive transient immunity standards?

Yes, the SMAJ170 meets ISO 7637-2 requirements for Pulse 1 (inductive load disconnect), Pulse 2a (sudden load removal), Pulse 2b (supply interruption), Pulse 3a (capacitive coupling), and Pulse 3b (ground noise). Its 400 W peak pulse power rating, fast <1.0 ps response, and specified clamping behavior under 10/1000 µs waveforms directly support compliance. System-level validation is still required, but the SMAJ170 provides the foundational protection needed for automotive-grade 24 V and 48 V subsystems.

What is the operating temperature range for the SMAJ170, and how does it affect power rating?

Its operating junction temperature range is −55°C to +150°C. Peak pulse power is rated at 400 W only at T_A = 25°C; above that, power must be derated linearly per the Pulse Derating Curve (Fig.2 in the datasheet). At 125°C ambient, the usable P_PPM drops to approximately 200 W. This derating is critical for under-hood or enclosed industrial applications-designers must calculate worst-case ambient + self-heating to confirm margin. The SMAJ170 maintains full specification compliance across this full range.

Can the SMAJ170 be used in place of SMAJ170A, and what are the trade-offs?

No direct substitution is recommended without circuit review: SMAJ170 has a wider V_BR range (189–231 V) and higher V_C (304 V), while SMAJ170A offers tighter V_BR (189–209 V) and lower V_C (275 V). Using SMAJ170 in an SMAJ170A-designed circuit may result in later clamping onset and higher transient voltage stress. Conversely, substituting SMAJ170A may cause premature conduction in high-tolerance systems. Always validate clamping timing and voltage margins with actual surge waveforms when changing between these variants. The SMAJ170 remains optimal for cost-sensitive, high-volume applications where broader tolerance is acceptable.

SMAJ170 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):: 170V

Voltage - Breakdown (Min):: 189V

Voltage - Clamping (Max) @ Ipp:: 304V

Current - Peak Pulse (10/1000µs):: 1A

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)

SMAJ170 FAQ

1.How can I place an order for SMAJ170 through Aetrix?

Please submit a Request for Quotation (RFQ) for SMAJ170 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 SMAJ170 reliable?

The price and inventory of SMAJ170 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMAJ170 is usually 5 days.

3.What payment methods are accepted for SMAJ170?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMAJ170 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for SMAJ170?

SMAJ170 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SMAJ170 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 SMAJ170?

For technical support, including SMAJ170 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMAJ170 requirements.

6.How does Aetrix verify that SMAJ170 is sourced from the original manufacturer or authorized distributors?

All SMAJ170 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 SMAJ170 meets industry standards.

7.What is the process for return or replacement of SMAJ170?

All SMAJ170 units undergo pre-shipment inspection (PSI). If there is an issue with SMAJ170, 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 SMAJ170 part is unused and in its original packaging.

Return procedure for SMAJ170:

1.Submit a request within 90 days.

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

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