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onsemi 1SMB18AT3
- Part No.:
- 1SMB18AT3
- Manufacturer:
- onsemi
- Category:
- TVS Diodes
- Package:
- -
- Datasheet:
-
1SMB18AT3.pdf
- Description:
- TVS DIODE 18V 29.2V SMB
- Quantity:
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- Shipping:
Inventory:7,229
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Product details
Overview
1SMB18AT3 from ON Semiconductor is a unidirectional 600 W peak power Zener transient voltage suppressor (TVS) in SMB package, designed for parallel overvoltage protection of sensitive electronics. It features a 18 V working peak reverse voltage (VRWM), 22.1 V minimum breakdown voltage (VBR) at 1 mA test current, and clamps to ≤29.2 V at 20.5 A peak pulse current (IPP), making it suitable for automotive power line surge suppression and industrial power supply input protection.
For engineers reviewing the 1SMB18AT3 datasheet, pinout, applications, or equivalent options, this device is selected for robust, sub-1 ns response transient suppression where low clamping voltage, high surge capability, and UL 497B certification for isolated loop circuits are required.
Technical Context
The 1SMB18AT3 operates as a unidirectional Zener-based TVS diode with avalanche breakdown mechanism, optimized for single-polarity transients. Its electrical behavior is defined by three key voltage thresholds: VRWM = 18 V (maximum continuous reverse voltage), VBR = 22.1–24.5 V (breakdown range at IT = 1 mA), and VC = 29.2 V (clamping voltage at IPP = 20.5 A).
Thermal design relies on junction-to-lead thermal resistance (RJL = 40 °C/W) and derating above 75 °C, while mechanical construction uses ON Semiconductor's Surmetic™ SMB package (Case 403A) with modified L-bend leads, Pb-free plating, and 260 °C soldering tolerance for surface-mount reliability.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Peak Power Dissipation | 600 W @ 1 ms pulse - enables handling of IEC 61000-4-5 Level 4 surges without failure |
| Working Peak Reverse Voltage (VRWM) | 18 V - sets maximum continuous DC or peak AC operating voltage before leakage exceeds 5 µA |
| Breakdown Voltage (VBR) | 22.1 V min / 24.5 V max @ IT = 1 mA - defines precise avalanche onset threshold for predictable clamping initiation |
| Clamping Voltage (VC) | ≤29.2 V @ IPP = 20.5 A - ensures protected circuit sees no more than 29.2 V during worst-case transient |
| Response Time | <1.0 ns - limits voltage overshoot during fast-rising ESD or lightning-induced transients |
| ESD Rating | Class 3 (>16 kV HBM) - qualifies for direct human-contact interface protection per ANSI/ESDA JS-001 |
| UL Recognition | UL 497B (QVGQ2) - certified for use in isolated loop circuit protection applications including telecom and process control |
Pinout & Package
1SMB18AT3 is housed in ON Semiconductor's Surmetic™ SMB plastic surface-mount package (Case 403A), featuring a cathode-indicating polarity band and modified L-bend leads for enhanced pad adhesion. The device has two terminals: anode and cathode, with unidirectional conduction from anode to cathode.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Current entry terminal under forward bias; connected to system ground or low-side reference in TVS configuration | Provides low VF path (<3.5 V @ 30 A) for fault current return during clamping; must be routed with minimal inductance |
| Cathode | Current exit terminal under reverse bias; connected to protected line (e.g., 12 V rail, CAN_H) | Carries full surge current during transient; polarity band identifies this terminal for correct PCB orientation |
Key Features
| Feature | Design Value |
|---|---|
| 600 W peak pulse power rating | Supports IEC 61000-4-5 4th-level surge immunity (4 kV/2 Ω) without degradation in standard PCB layouts |
| Low clamping ratio (VC/VBR ≈ 1.32) | Minimizes overvoltage stress on downstream ICs compared to higher-ratio TVS devices |
| UL 497B recognition (QVGQ2) | Validates suitability for safety-critical isolated loop protection in medical and industrial control systems |
| Pb-free Surmetic™ SMB package | Enables RoHS-compliant manufacturing with 260 °C reflow compatibility and corrosion-resistant finish |
| Sub-1 ns response time | Reduces transient-induced logic upset and latch-up risk in high-speed digital interfaces |
Applications
| Automotive Power Line Protection | Industrial PLC Input Protection |
|---|---|
Use Scenario: Suppressing load-dump and jump-start transients on 12 V battery-fed ECUs and body control modules. IC Role / Device Role / Timing Role: Unidirectional TVS placed between battery rail and local regulator input, clamping spikes within nanoseconds. Use Value: Limits voltage to ≤29.2 V during 100 A/100 ms load dump events, preventing damage to 3.3 V/5 V LDOs and microcontrollers. |
Use Scenario: Protecting 24 V DC digital input channels of programmable logic controllers against field-wiring induced surges. IC Role / Device Role / Timing Role: Parallel-connected TVS on each input channel, referenced to common ground, absorbing energy from inductive coil switching. Use Value: Withstands repeated 600 W transients per IEC 61000-4-4, maintaining signal integrity and eliminating false triggering in discrete I/O modules. |
| Medical Equipment Power Supply | Telecom Isolated Loop Interface |
Use Scenario: Safeguarding front-end rectifiers and PFC stages in Class II medical-grade AC/DC adapters. IC Role / Device Role / Timing Role: Primary-side TVS across bulk capacitor input, triggered by line-to-line or line-to-ground surges. Use Value: UL 497B certification ensures compliance with patient-connected equipment isolation requirements while clamping to 29.2 V. |
Use Scenario: Protecting RS-485 or analog current-loop (4–20 mA) transmitter outputs in building automation systems. IC Role / Device Role / Timing Role: Unidirectional TVS on signal line side of isolation barrier, referenced to isolated ground. Use Value: Enables UL 497B–compliant isolated loop protection without compromising galvanic separation integrity or noise immunity. |
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 rated for 600 W @ 10/1000 µs waveform (vs. 1 ms for 1SMB18AT3); slightly higher Ctyp = 915 pF | Better suited for shorter-duration transients (e.g., ESD, fast EFT); less margin for long-duration load dump | Select SMBJ18A when surge profile matches 10/1000 µs; verify layout inductance does not elevate overshoot beyond 1SMB18AT3's advantage in slower events |
| 1.5SMC18A | Higher package thermal mass (SMC vs. SMB); same VRWM and VC, but 1.5 kW peak power rating and larger footprint (7.11 × 6.22 mm) | Used where board space allows and higher single-pulse energy absorption is needed (e.g., main AC input stage) | Choose 1.5SMC18A only if 1.5 kW rating is required and PCB real estate permits larger case; otherwise 1SMB18AT3 offers optimal density for secondary rails |
Compared with SMBJ18A and 1.5SMC18A, the 1SMB18AT3 delivers best-in-class balance of compact SMB footprint, 1 ms surge capability, and UL 497B certification-making it preferred for space-constrained, safety-certified 12–24 V industrial and automotive subsystems.
Availability
1SMB18AT3 is available at Aetrix Electronics and suitable for automotive infotainment power conditioning, industrial PLC digital input protection, and medical AC/DC adapter surge suppression requiring stable component supply and full traceability.
Supply support for 1SMB18AT3 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 1SMB18AT3 belongs to the 1SMBxxAT3 series of unidirectional Zener TVS diodes, engineered specifically for high-reliability, UL-certified transient suppression in harsh environments where compact size and consistent clamping performance are critical.
FAQ
What is the maximum clamping voltage of the 1SMB18AT3 under peak surge conditions?
The 1SMB18AT3 clamps to a maximum of 29.2 V when subjected to its rated peak pulse current of 20.5 A (1 ms pulse). This value is measured per the standard 10 × 1000 µs waveform definition in ON Semiconductor's datasheet and represents the upper limit of voltage seen by protected circuitry during worst-case transient events.
Does the 1SMB18AT3 meet UL 497B requirements for isolated loop protection?
Yes, the 1SMB18AT3 carries UL 497B recognition under file QVGQ2, explicitly certified for use in isolated loop circuit protection. This includes passing strike voltage breakdown, endurance conditioning, dielectric withstand, and discharge tests-validating its suitability in medical, telecom, and process control applications requiring reinforced isolation.
What is the thermal derating behavior of the 1SMB18AT3 above 75°C lead temperature?
The 1SMB18AT3 derates linearly above 75°C lead temperature at 25 mW/°C, reducing its DC power dissipation from 3.0 W at 75°C to zero at approximately 195°C. This derating applies to steady-state power; transient surge capability remains unaffected as long as junction temperature stays within −65°C to +150°C limits.
Can the 1SMB18AT3 be used in bidirectional transient protection applications?
No, the 1SMB18AT3 is strictly unidirectional. Its internal Zener structure conducts only in reverse breakdown mode and blocks forward current above ~3.5 V. For bidirectional protection, ON Semiconductor offers the 1SMB18CAT3 variant (with "C" suffix), which provides symmetrical clamping for AC lines or differential signals.
What is the typical junction capacitance of the 1SMB18AT3 at zero bias?
The typical junction capacitance of the 1SMB18AT3 is 870 pF at 0 V bias and 1 MHz, as specified in the Electrical Characteristics table on page 3 of the ON Semiconductor datasheet. This value decreases with increasing reverse bias and must be accounted for in high-frequency signal path designs to avoid bandwidth reduction or signal distortion.
1SMB18AT3 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Package/Case:
- -
- Series:
- -
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Type:
- -
- Unidirectional Channels:
- -
- Bidirectional Channels:
- -
- Voltage - Reverse Standoff (Typ):
- -
- Voltage - Breakdown (Min):
- -
- Voltage - Clamping (Max) @ Ipp:
- -
- Current - Peak Pulse (10/1000µs):
- -
- Power - Peak Pulse:
- -
- Power Line Protection:
- -
- Applications:
- -
- Capacitance @ Frequency:
- -
- Operating Temperature:
- -
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- -
- Supplier Device Package:
- -
1SMB18AT3 FAQ
1.How can I place an order for 1SMB18AT3 through Aetrix?
Please submit a Request for Quotation (RFQ) for 1SMB18AT3 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 1SMB18AT3 reliable?
The price and inventory of 1SMB18AT3 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 1SMB18AT3 is usually 5 days.
3.What payment methods are accepted for 1SMB18AT3?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 1SMB18AT3 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 1SMB18AT3?
1SMB18AT3 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 1SMB18AT3 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 1SMB18AT3?
For technical support, including 1SMB18AT3 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 1SMB18AT3 requirements.
6.How does Aetrix verify that 1SMB18AT3 is sourced from the original manufacturer or authorized distributors?
All 1SMB18AT3 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 1SMB18AT3 meets industry standards.
7.What is the process for return or replacement of 1SMB18AT3?
All 1SMB18AT3 units undergo pre-shipment inspection (PSI). If there is an issue with 1SMB18AT3, 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 1SMB18AT3 part is unused and in its original packaging.
Return procedure for 1SMB18AT3:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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