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onsemi 1SMC18AT3
- Part No.:
- 1SMC18AT3
- Manufacturer:
- onsemi
- Category:
- TVS Diodes
- Package:
- DO-214AB, SMC
- Datasheet:
-
1SMC18AT3.pdf
- Description:
- TVS DIODE 18VWM 29.2VC SMC
- Quantity:
- Payment:
- Shipping:
Inventory:4,097
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Product details
Overview
1SMC18AT3 from ON Semiconductor is a unidirectional 1500 W transient voltage suppressor (TVS) diode designed for parallel clamping protection of sensitive electronics against ESD, lightning-induced surges, and inductive switching transients. It features a 18 V working peak reverse voltage (VRWM), 22.1 V nominal breakdown voltage (VBR) at 1 A test current, 29.2 V maximum clamping voltage (VC) at 51.4 A peak pulse current, and sub-1 ns response time. It is used in automotive power line protection, industrial PLC I/O modules, and DC power supply input stages.
For engineers reviewing the 1SMC18AT3 datasheet, pinout, applications, or equivalent options, key selection criteria include clamping voltage margin relative to protected circuit's absolute maximum rating, peak pulse current capability under 1 ms 10/1000 µs waveform, UL 497B certification for isolated loop circuits, and SMC package thermal performance with 54.6 °C/W junction-to-lead resistance.
Technical Context
The 1SMC18AT3 operates as a Zener-based unidirectional TVS diode, entering avalanche conduction when reverse voltage exceeds its specified breakdown threshold. Its low dynamic impedance ensures stable clamping during high-current transients, while its thermally robust Surmetic SMC package enables reliable heat dissipation under repeated surge events.
It is rated for 1500 W non-repetitive peak pulse power per 1 ms 10/1000 µs waveform, with derating above 75°C lead temperature. The device exhibits <5 µA leakage at VRWM and meets Class 3 (>16 kV) HBM ESD immunity, making it suitable for environments requiring robust electrostatic discharge hardening without active control circuitry.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VRWM | 18 V - Maximum continuous reverse operating voltage before clamping begins; sets minimum system voltage margin for safe operation. |
| VBR (min/typ/max) | 20 / 22.1 / 24.5 V @ 1 A - Confirmed avalanche onset range; determines worst-case turn-on threshold under production tolerance. |
| VC @ IPP | 29.2 V @ 51.4 A - Maximum clamped voltage during 1 ms surge; must stay below protected IC's absolute maximum rating. |
| PPK | 1500 W @ 1 ms - Peak transient energy absorption capacity; defines survivability against standardized lightning/surge waveforms. |
| Response Time | <1 ns - Enables suppression before transient overshoot damages downstream logic or analog circuitry. |
| Leakage Current | <5 µA @ VRWM - Ensures negligible standby power loss and no signal integrity impact in high-impedance sensing paths. |
| UL Recognition | UL 497B (QVGQ2 File #E210057) - Certified for use in isolated loop circuit protection, including telecom and industrial fieldbus interfaces. |
Pinout & Package
1SMC18AT3 is housed in the SMC (DO-214AB) surface-mount package (Case 403), featuring a molded polarity notch indicating the cathode terminal. The package uses void-free thermosetting plastic, modified L-bend leads for enhanced solder joint reliability, and Pb-free plating compliant with RoHS.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Reverse-biased reference terminal | Connected to system ground or lower-potential rail; forms current return path during clamping event. |
| Cathode | Transient voltage clamp node | Connected to protected line (e.g., 24 V supply rail); conducts surge current to ground when voltage exceeds VRWM. |
Key Features
| Feature | Design Value |
|---|---|
| 1500 W peak pulse power | Withstands IEC 61000-4-5 Level 4 (4 kV/2 Ω) surges on 24 V industrial lines without degradation. |
| UL 497B recognition | Validated for safety-critical isolated loop protection in process control and medical auxiliary circuits. |
| ESD immunity >16 kV HBM | Eliminates need for additional ESD protection stages in front-end interfaces exposed to handling or connector mating. |
| Low clamping ratio (VC/VBR ≈ 1.32) | Minimizes overvoltage stress on downstream components compared to higher-ratio TVS devices. |
| Thermal resistance RJL = 54.6 °C/W | Supports sustained surge duty cycles in enclosed enclosures with limited airflow, per derating curve Figure 3. |
Applications
| Automotive Power Line Protection | Industrial PLC Digital Input Modules |
|---|---|
|
Use Scenario: 12 V/24 V battery-fed ECUs subjected to load dump (ISO 7637-2 Pulse 5a) and alternator ripple. IC Role / Device Role / Timing Role: Unidirectional clamping diode placed between power rail and chassis ground to shunt surge energy before reaching PMIC or microcontroller. Use Value: Clamps to 29.2 V within 1 ns, staying below 36 V absolute max rating of typical automotive-grade MCUs and CAN transceivers. |
Use Scenario: 24 V DC digital input channels in programmable logic controllers interfacing with field sensors and switches. IC Role / Device Role / Timing Role: Primary overvoltage protector on each input channel, mounted adjacent to terminal block to minimize trace inductance. Use Value: UL 497B certification ensures compliance with industrial isolation barrier requirements; 51.4 A IPP handles induced surges from nearby motor contactors. |
| Medical Equipment Power Supplies | Telecom DC Feeds (POTS/DSL) |
|
Use Scenario: Secondary-side 24 V output rails in AC/DC adapters powering diagnostic imaging peripherals. IC Role / Device Role / Timing Role: Final-stage transient suppressor after bulk filtering and before linear regulators or ADC reference supplies. Use Value: Sub-5 µA leakage prevents drift in precision analog front-ends; 1500 W rating covers EN 61000-4-4 EFT bursts without thermal runaway. |
Use Scenario: DC feed lines in legacy telephone exchange equipment and DSLAM line cards carrying -48 V phantom power. IC Role / Device Role / Timing Role: Bidirectional protection is not required; unidirectional 1SMC18AT3 protects negative-rail-connected circuitry from positive-going surges. Use Value: 18 V VRWM matches standard -48 V system derating rules (|−48| × 0.375 = 18 V), ensuring reliable blocking during normal operation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient voltage suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMBJ18A | Same VRWM (18 V) and VC (29.2 V), but lower PPK (600 W) and smaller SMB package (RJA = 165 °C/W vs. 54.6 °C/W). | Limited to lower-energy transients; unsuitable for IEC 61000-4-5 Level 4 or automotive load dump. | Select 1SMC18AT3 where sustained surge energy or thermal cycling reliability is critical; SMBJ18A fits space-constrained layouts. |
| 1.5SMC18A | Identical electrical specs and SMC package, but obsolete marking (no 'T3' suffix) and older revision; same UL 497B listing and thermal performance. | No functional difference; may lack latest manufacturing controls or Pb-free compliance documentation. | 1SMC18AT3 is preferred for new designs due to documented Pb-free status ('G' suffix) and current production support. |
Compared with SMBJ18A and 1.5SMC18A, the 1SMC18AT3 delivers superior thermal management for repetitive surge events, guaranteed Pb-free compliance, and full UL 497B certification-making it the optimal choice for industrial and automotive applications demanding long-term reliability and regulatory alignment.
Availability
1SMC18AT3 is available at Aetrix Electronics and suitable for automotive ECUs, industrial PLC I/O modules, and medical power supply designs requiring stable component supply, full regulatory documentation, and long-term lifecycle assurance.
Supply support for 1SMC18AT3 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 is a global semiconductor manufacturer specializing in power management, analog, sensor, and discrete solutions for automotive, industrial, and communications markets.
The 1SMC18AT3 belongs to the SMC-series Zener TVS family, engineered specifically for high-energy transient suppression in harsh environments where reliability, UL certification, and thermal robustness are mandatory.
FAQ
What is the clamping voltage of the 1SMC18AT3 at its rated peak pulse current?
The 1SMC18AT3 has a maximum clamping voltage (VC) of 29.2 V at its rated peak pulse current (IPP) of 51.4 A, measured under the standard 1 ms 10/1000 µs waveform. This value is guaranteed across temperature and production lot, and defines the upper voltage limit imposed on protected circuitry during surge events. Designers must verify that 29.2 V remains safely below the absolute maximum rating of downstream components.
Is the 1SMC18AT3 suitable for bidirectional transient protection?
No, the 1SMC18AT3 is a unidirectional TVS diode and is not rated for bidirectional operation. Its electrical characteristics-including breakdown voltage, clamping behavior, and leakage-are specified only for reverse-bias conditions. For AC or dual-polarity signal lines, a dedicated bidirectional device such as the 1SMC18AT3's counterpart in the 1SMCxxCA series must be selected instead.
Does the 1SMC18AT3 meet UL 497B certification, and what does that mean for my design?
Yes, the 1SMC18AT3 carries UL 497B recognition (File #E210057, category QVGQ2) for isolated loop circuit protection. This certification validates performance in strike voltage breakdown, endurance conditioning, dielectric withstand, and discharge testing-ensuring suitability for telecom, industrial fieldbus, and medical auxiliary circuits where galvanic isolation integrity is safety-critical.
What is the thermal resistance and maximum power derating behavior of the 1SMC18AT3?
The 1SMC18AT3 has a junction-to-lead thermal resistance (RJL) of 54.6 °C/W and is rated for 4.0 W DC power dissipation at TL = 75°C, derating linearly above that temperature. Its 1500 W peak pulse rating applies only at TL = 25°C and must be reduced per Figure 3 of the datasheet when lead temperature exceeds 75°C-critical for enclosed or high-ambient-temperature deployments.
How does the 1SMC18AT3 compare to the older 1.5SMC18A in terms of manufacturability and compliance?
The 1SMC18AT3 supersedes the 1.5SMC18A with explicit Pb-free packaging ('G' suffix), updated Surmetic molding process controls, and current production status. While both share identical electrical specs and SMC package dimensions, the 1SMC18AT3 provides documented RoHS compliance, enhanced traceability, and ongoing lifecycle support-making it the recommended version for all new designs.
1SMC18AT3 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Package/Case:
- DO-214AB, SMC
- 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):
- 51.4A
- Power - Peak Pulse:
- 1500W (1.5kW)
- Power Line Protection:
- No
- Applications:
- General Purpose
- Capacitance @ Frequency:
- -
- Operating Temperature:
- -65°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SMC
1SMC18AT3 FAQ
1.How can I place an order for 1SMC18AT3 through Aetrix?
Please submit a Request for Quotation (RFQ) for 1SMC18AT3 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 1SMC18AT3 reliable?
The price and inventory of 1SMC18AT3 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 1SMC18AT3 is usually 5 days.
3.What payment methods are accepted for 1SMC18AT3?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 1SMC18AT3 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 1SMC18AT3?
1SMC18AT3 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 1SMC18AT3 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 1SMC18AT3?
For technical support, including 1SMC18AT3 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 1SMC18AT3 requirements.
6.How does Aetrix verify that 1SMC18AT3 is sourced from the original manufacturer or authorized distributors?
All 1SMC18AT3 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 1SMC18AT3 meets industry standards.
7.What is the process for return or replacement of 1SMC18AT3?
All 1SMC18AT3 units undergo pre-shipment inspection (PSI). If there is an issue with 1SMC18AT3, 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 1SMC18AT3 part is unused and in its original packaging.
Return procedure for 1SMC18AT3:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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