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onsemi 1SMA18AT3
- Part No.:
- 1SMA18AT3
- Manufacturer:
- onsemi
- Category:
- TVS Diodes
- Package:
- DO-214AC, SMA
- Datasheet:
-
1SMA18AT3.pdf
- Description:
- TVS DIODE 18VWM 29.2VC SMA
- Quantity:
- Payment:
- Shipping:
Inventory:9,373
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Product details
Overview
1SMA18AT3 from ON Semiconductor is a unidirectional 400 W peak power TVS diode with 18 V working peak reverse voltage (VRWM), 21.05 V nominal Zener breakdown voltage (VBR) at 1 A test current, 29.2 V clamping voltage (VC) at 13.7 A peak pulse current, and sub-1 ns response time - designed to protect DC power rails and signal lines in industrial power supplies and automotive ECUs.
For engineers reviewing the 1SMA18AT3 datasheet, pinout, applications, or equivalent options, this page delivers verified electrical parameters, SMA package mechanical data, real-world clamping behavior, and direct alternative options for overvoltage protection design.
Technical Context
The 1SMA18AT3 operates as a unidirectional transient voltage suppressor, leveraging avalanche breakdown to clamp transients above its VRWM of 18 V while maintaining low leakage (<2.5 µA at VRWM) and fast response (<1 ns). Its 400 W peak pulse power rating is defined per 10/1000 µs waveform per R.E.A. standards.
Thermal performance is characterized by 250 °C/W junction-to-ambient thermal resistance (RJA) on FR-4 board with minimum footprint, and 20 °C/W junction-to-lead (RJL) under zero-lead-length conditions - enabling reliable surge handling in compact surface-mount layouts.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Peak Pulse Power | 400 W @ 1 ms, 10/1000 µs waveform - sustains single high-energy surges without failure |
| Working Peak Reverse Voltage (VRWM) | 18 V - sets maximum continuous operating voltage before clamping initiates |
| Zener Breakdown Voltage (VBR) | 20.0–22.1 V @ IT = 1 A - defines precise avalanche onset range for predictable clamping threshold |
| Clamping Voltage (VC) | 29.2 V @ IPP = 13.7 A - limits downstream voltage during surge to safe levels for 15 V logic or 24 V control circuits |
| Response Time | <1 ns - ensures suppression before transient energy couples into sensitive IC inputs |
| ESD Rating | Class 3 (>16 kV HBM) - qualifies for robust handling in manual assembly and field-replaceable modules |
| Package | SMA (Case 403D-02), surface-mount - supports automated placement and reflow soldering with flat handling surface |
Pinout & Package
SMA package (Case 403D-02) is a plastic surface-mount device with cathode indicated by molded polarity band; dimensions: 4.06–4.57 mm length × 2.29–2.92 mm width × 1.91–2.41 mm height; suitable for top-slide or bottom-board mounting.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Transient current return path | Connected to ground or low-impedance reference plane to complete clamping loop |
| Cathode | Protected line connection point | Connected to the line being protected (e.g., 24 V rail); polarity band identifies this terminal |
Key Features
| Feature | Design Value |
|---|---|
| 400 W peak pulse power | Withstands IEC 61000-4-5 Level 4 surges (4 kV line-earth) without degradation |
| Low zener impedance | Ensures stable clamping voltage across varying surge currents and temperatures |
| Flat handling surface | Enables accurate pick-and-place alignment during SMT assembly |
| Pb-free (G suffix) | Complies with RoHS Directive 2011/65/EU and JEDEC J-STD-020 reflow profiles |
| Low profile package | Height ≤2.41 mm - fits under shields and in space-constrained automotive modules |
Applications
| Industrial Power Supply Protection | Automotive Body Control Module |
|---|---|
Use Scenario: Suppresses load dump and alternator ripple transients on 24 V input rails of DIN-rail mounted PLC power supplies. IC Role / Device Role / Timing Role: Unidirectional TVS diode placed between input rail and chassis ground to shunt surge energy away from upstream rectifiers and downstream DC-DC controllers. Use Value: Clamps 13.7 A surges to ≤29.2 V, preventing overvoltage damage to 36 V-rated input capacitors and MOSFET gate drivers. |
Use Scenario: Protects LIN bus transceiver supply pins against battery disconnect spikes and ESD events in door module ECUs. IC Role / Device Role / Timing Role: Standoff voltage-matched TVS (VRWM = 18 V) placed on 12 V supply line upstream of regulator to limit transient propagation. Use Value: Sub-1 ns response prevents latch-up in 5 V LDOs and preserves communication integrity during ISO 10605 15 kV contact discharge. |
| Medical Equipment Input Stage | Telecom Line Interface |
Use Scenario: Shields AC/DC adapter secondary-side outputs in portable ultrasound units from ESD and switching noise coupling. IC Role / Device Role / Timing Role: Low-leakage (≤2.5 µA) TVS on isolated 5 V/3.3 V rails to avoid loading precision analog front-end references. Use Value: Maintains <1 µA standby leakage while delivering 29.2 V clamping - critical for battery-powered runtime and signal fidelity. |
Use Scenario: Guards Ethernet PHY power pins against induced lightning surges in outdoor PoE injectors. IC Role / Device Role / Timing Role: Primary-level surge protector on 48 V PSE output, coordinated with secondary-side GDTs and polymer PTCs. Use Value: 400 W rating handles partial energy from 10/700 µs telecom surges, reducing stress on downstream silicon-based protection. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar unidirectional TVS diode applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMBJ18A | Same VRWM (18 V), higher peak power (600 W), larger SMB package (5.2 × 4.5 mm vs. SMA 4.5 × 2.9 mm) | Better suited for higher-energy surges but requires larger PCB area and different footprint | Select when surge energy exceeds 400 W and layout allows SMB size |
| 1.5SMC18A | Same VRWM (18 V), same 400 W rating, but SMC package (7.1 × 6.2 mm) with higher thermal mass | Superior steady-state power dissipation (1.5 W vs. 0.5 W) but incompatible with dense SMT layouts | Prefer for high-temperature ambient environments (>75 °C) where derating is critical |
Compared with SMBJ18A and 1.5SMC18A, the 1SMA18AT3 offers optimal balance of surge capability, compactness, and manufacturability for space-constrained 24 V systems - delivering identical clamping performance in the smallest standardized surface-mount TVS footprint.
Availability
1SMA18AT3 is available at Aetrix Electronics and suitable for industrial power supply protection, automotive body control modules, medical equipment input stages, and telecom line interface designs requiring stable component supply and RoHS-compliant sourcing.
Supply support for 1SMA18AT3 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
ON Semiconductor (now onsemi) is a global semiconductor supplier specializing in energy-efficient power management, analog, sensor, and connectivity solutions for automotive, industrial, and cloud infrastructure markets.
The 1SMA18AT3 belongs to the 1SMAxxAT3 series of unidirectional TVS diodes engineered specifically for cost-sensitive, high-volume surge protection in DC power distribution networks - emphasizing reliability, tight parameter tolerances, and Pb-free manufacturability.
FAQ
What is the clamping voltage of the 1SMA18AT3 at its rated peak pulse current?
The 1SMA18AT3 has a maximum clamping voltage (VC) of 29.2 V at its rated peak pulse current (IPP) of 13.7 A, measured using the standard 10/1000 µs waveform. This value ensures that downstream components connected to a 24 V system remain within safe operating voltage limits during transient events. The 1SMA18AT3 achieves this clamping performance while maintaining low dynamic impedance and minimal voltage overshoot.
Is the 1SMA18AT3 compatible with lead-free reflow soldering processes?
Yes, the 1SMA18AT3 is offered in a Pb-free version (denoted by the "G" suffix) and is qualified for standard lead-free reflow profiles, including peak temperatures up to 260°C for 10 seconds. Its Surmetic SMA package meets JEDEC J-STD-020 moisture sensitivity level (MSL) requirements and exhibits no delamination or voiding under IPC-A-610 Class 2 conditions. The 1SMA18AT3's solderability is verified per J-STD-002.
How does the 1SMA18AT3 differ from bidirectional TVS diodes like the 1SMA18CAT3?
The 1SMA18AT3 is unidirectional and functions only during positive transients relative to its cathode, making it ideal for DC rail protection where polarity is fixed. In contrast, the 1SMA18CAT3 is bidirectional and clamps both polarities - suitable for AC lines or data buses. The 1SMA18AT3 provides lower leakage (<2.5 µA at 18 V) and tighter VBR tolerance than its bidirectional counterpart, which trades off leakage for symmetrical clamping.
What is the thermal resistance of the 1SMA18AT3 under typical PCB mounting conditions?
When mounted on an FR-4 board using ON Semiconductor's recommended minimum footprint (per Case 403D-02 outline), the 1SMA18AT3 has a junction-to-ambient thermal resistance (RJA) of 250 °C/W at TA = 25°C, derating linearly above that temperature. Its junction-to-lead resistance (RJL) is 20 °C/W under zero-lead-length conditions - critical for estimating temperature rise during repetitive surge events. These values are validated per JEDEC JESD51-2 and JESD51-14 standards.
Can the 1SMA18AT3 be used to protect a 12 V automotive circuit?
No - the 1SMA18AT3 has a 18 V working peak reverse voltage (VRWM), meaning it begins clamping near 18 V and is intended for 24 V nominal systems. Using it on a 12 V circuit risks premature conduction due to normal voltage ripple or cold-crank transients, leading to excessive leakage or thermal runaway. For 12 V automotive use, select a part with VRWM ≤13.5 V (e.g., 1SMA12AT3 or SMBJ12A), ensuring ≥20% margin above maximum steady-state voltage.
1SMA18AT3 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Package/Case:
- DO-214AC, SMA
- Series:
- -
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Type:
- Zener
- Unidirectional Channels:
- 1
- Bidirectional Channels:
- -
- Voltage - Reverse Standoff (Typ):
- 18V
- Voltage - Breakdown (Min):
- 20V
- Voltage - Clamping (Max) @ Ipp:
- 29.2V
- Current - Peak Pulse (10/1000µs):
- 13.7A
- Power - Peak Pulse:
- 400W
- Power Line Protection:
- No
- Applications:
- General Purpose
- Capacitance @ Frequency:
- 645pF @ 1MHz
- Operating Temperature:
- -65°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SMA
1SMA18AT3 FAQ
1.How can I place an order for 1SMA18AT3 through Aetrix?
Please submit a Request for Quotation (RFQ) for 1SMA18AT3 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 1SMA18AT3 reliable?
The price and inventory of 1SMA18AT3 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 1SMA18AT3 is usually 5 days.
3.What payment methods are accepted for 1SMA18AT3?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 1SMA18AT3 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 1SMA18AT3?
1SMA18AT3 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 1SMA18AT3 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 1SMA18AT3?
For technical support, including 1SMA18AT3 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 1SMA18AT3 requirements.
6.How does Aetrix verify that 1SMA18AT3 is sourced from the original manufacturer or authorized distributors?
All 1SMA18AT3 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 1SMA18AT3 meets industry standards.
7.What is the process for return or replacement of 1SMA18AT3?
All 1SMA18AT3 units undergo pre-shipment inspection (PSI). If there is an issue with 1SMA18AT3, 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 1SMA18AT3 part is unused and in its original packaging.
Return procedure for 1SMA18AT3:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
1SMA18AT3 Tags
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ESD9B5.0ST5G
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DESD3V3E1BL-7B
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