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STMicroelectronics SMA4F18A
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- Part No.:
- SMA4F18A
- Manufacturer:
- STMicroelectronics
- Category:
- TVS Diodes
- Package:
- DO-221AC, SMA Flat Leads
- Datasheet:
-
SMA4F18A.pdf
- Description:
- TVS DIODE 18VWM 39.3VC SMAFLAT
- Quantity:
- Payment:
- Shipping:
Inventory:3,431
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Product details
Overview
SMA4F18A from STMicroelectronics is a unidirectional 400 W transient voltage suppression (TVS) diode designed for primary-level surge protection in DC power rails and signal lines. It features a 18 V stand-off voltage (VRM), 29.2 V clamping voltage at 13.7 A (10/1000 µs), 0.2 µA leakage at 25 °C, and operates up to 175 °C junction temperature - deployed in industrial power supplies and automotive body control modules.
For engineers reviewing the SMA4F18A datasheet, SMA4F18A pinout, SMA4F18A application, or SMA4F18A equivalent, key selection criteria include clamping performance under IEC 61000-4-2 Level 4 (±25 kV contact / ±30 kV air), thermal derating above 25 °C, unidirectional polarity constraint, and SMA flat-package soldering compatibility per J-STD-020 MSL level 1.
Technical Context
The SMA4F18A employs planar silicon avalanche technology optimized for low leakage and high-temperature reliability. Its breakdown voltage (VBR) is specified at 20–22.2 V (min–max, 1 mA test current), with dynamic resistance (RD) of 0.511 Ω enabling tight clamping under fast transients.
It delivers 400 W peak pulse power (10/1000 µs) at 25 °C ambient, derating to 200 W at Tj = 175 °C. The device complies with IEC 61000-4-2 (150 pF/330 Ω), UL94 V0, and JEDEC-standard footprint - supporting robust ESD and lightning surge immunity without parasitic capacitance degradation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Stand-off Voltage (VRM) | 18 V - maximum continuous reverse operating voltage before significant leakage begins |
| Breakdown Voltage (VBR) | 20–22.2 V @ 1 mA - precise avalanche initiation threshold ensuring predictable turn-on |
| Clamping Voltage (VCL) | 29.2 V @ 13.7 A (10/1000 µs) - limits downstream voltage stress during surge events |
| Peak Pulse Power (PPP) | 400 W (10/1000 µs) - sustains high-energy transients without failure at 25 °C |
| Leakage Current (IRM) | 0.2 µA @ VRM, 25 °C - minimizes standby power loss in battery-backed or low-power circuits |
| Junction Temperature Range | −55 to +175 °C - enables deployment in under-hood automotive and industrial environments |
| ESD Rating | ±25 kV contact / ±30 kV air (IEC 61000-4-2 Level 4) - exceeds standard system-level ESD immunity requirements |
Pinout & Package
The SMA4F18A uses the industry-standard SMA (DO-214AC) flat package: 2.25–2.90 mm width (D), 5.00–5.35 mm length (E), 0.90–1.10 mm height (A), matte tin-plated leads, and JEDEC-compliant footprint.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Cathode (marked band) | Surge current sink node | Connected to protected line; conducts avalanche current to ground during overvoltage |
| Anode | Reference/return path | Typically tied to system ground or low-impedance return plane for effective clamping |
Key Features
| Feature | Design Value |
|---|---|
| High-temperature operation | Rated for continuous use up to 175 °C junction temperature - supports compact thermal design in enclosed enclosures |
| Low dynamic resistance | 0.511 Ω - ensures minimal voltage overshoot during fast-rising transients (e.g., ISO 7637-2 pulses) |
| Controlled leakage profile | 0.2 µA @ 25 °C, 1 µA @ 85 °C - preserves signal integrity in high-impedance sensor interfaces |
| Standardized reflow compatibility | MSL level 1, J-STD-020-compliant profile - enables automated SMT assembly without moisture sensitivity concerns |
| UL94 V0 flammability rating | Self-extinguishing epoxy molding compound - meets safety requirements for industrial and transportation end equipment |
Applications
| Industrial Power Supply Input Protection | Automotive Body Control Module (BCM) |
|---|---|
|
Use Scenario: 24 V DC input rail exposed to load dump and jump-start surges in factory automation controllers. IC Role / Device Role / Timing Role: Primary TVS clamp placed upstream of DC-DC converter input to limit transient voltage to ≤30 V. Use Value: Withstands 400 W (10/1000 µs) surges and maintains <0.2 µA leakage, preventing standby current drift in always-on systems. |
Use Scenario: LIN bus transceiver power supply line in door module subjected to ESD and cable discharge events. IC Role / Device Role / Timing Role: Unidirectional TVS connected between VCC and GND to suppress ±30 kV air-discharge transients per IEC 61000-4-2. Use Value: Clamps to 29.2 V within nanoseconds, protecting 5 V LDO regulator and MCU IO pins without latch-up risk. |
| Telecom Remote Radio Unit (RRU) DC Feeder | Smart Meter AC/DC Auxiliary Power Input |
|
Use Scenario: −48 V telecom power feed line vulnerable to induced lightning surges on outdoor antenna cables. IC Role / Device Role / Timing Role: First-stage surge protector mounted at entry point, coordinated with MOV and gas discharge tube. Use Value: Delivers 200 W clamping capability at 175 °C ambient, enabling reliable operation in uncooled outdoor cabinets. |
Use Scenario: 230 VAC-derived 12 V auxiliary supply in utility smart meters installed in hot, humid substations. IC Role / Device Role / Timing Role: Secondary TVS on rectified DC output to absorb switching noise and EFT bursts from nearby relays. Use Value: Maintains <1 µA leakage at 85 °C, avoiding cumulative error in precision metering reference circuits. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar unidirectional TVS diode applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMAJ18A (onsemi) | Same SMA package, 400 W rating, but higher VBR (20–22.1 V) and VCL (29.2 V @ 13.7 A); RD = 0.52 Ω | Identical IEC 61000-4-2 compliance; slightly lower thermal resistance (Rθj-a ≈ 100 °C/W vs. ST's 110 °C/W) | Preferred where tighter thermal margin is required in high-density PCB layouts |
| P6SMB18A (Littelfuse) | Same 18 V VRM, but 600 W rating (10/1000 µs); VCL = 29.2 V @ 20.5 A; RD = 0.45 Ω; larger SMB package | Higher surge capacity suits infrequent high-energy events (e.g., AC mains coupling); not drop-in due to footprint mismatch | Select when system-level testing reveals >400 W surge energy; requires PCB redesign for SMB pad layout |
Compared with SMAJ18A and P6SMB18A, the SMA4F18A offers optimal balance of low leakage (0.2 µA), JEDEC-standard SMA footprint, and verified 175 °C operation - making it ideal for space-constrained, thermally demanding embedded power rails where long-term reliability is critical.
Availability
SMA4F18A is available at Aetrix Electronics and suitable for industrial power supply input protection, automotive body control modules, telecom remote radio units, and smart meter auxiliary power inputs requiring stable component supply across extended temperature ranges and multi-year production cycles.
Supply support for SMA4F18A 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
STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, delivering microcontrollers, power devices, sensors, and analog ICs for industrial, automotive, and consumer markets.
The SMA4F series belongs to ST's Transil™ TVS portfolio, engineered specifically for high-reliability transient suppression in harsh-environment applications where low leakage, high-temperature stability, and repeatable clamping performance are mandatory.
FAQ
What is the maximum clamping voltage of SMA4F18A under a 10/1000 µs surge?
The maximum clamping voltage (VCL) is 29.2 V at 13.7 A for a 10/1000 µs waveform, measured at 25 °C ambient. This value increases with junction temperature per the αT coefficient (9.2 × 10⁻⁴/°C), reaching ~32.5 V at 125 °C junction temperature based on datasheet derating curves.
Can SMA4F18A be used in bidirectional configurations?
No - SMA4F18A is strictly unidirectional, with cathode marking indicating polarity-sensitive installation. For bidirectional protection, ST offers the SMA4F18CA variant; using SMA4F18A in reverse-biased configuration risks permanent breakdown above VRM due to its asymmetric avalanche structure.
Does SMA4F18A meet automotive AEC-Q200 requirements?
No - while rated for −55 to +175 °C operation and compliant with IEC 61000-4-2, SMA4F18A is not AEC-Q200 qualified. For automotive-grade TVS diodes, ST recommends the SMA6J18A or Automotive Transil™ series, which undergo full stress testing per AEC-Q200 Rev D.
What is the recommended PCB footprint for SMA4F18A?
The datasheet specifies a JEDEC-standard SMA (DO-214AC) footprint: 2.5 mm pad length, 1.5 mm pad width, 4.0 mm center-to-center spacing, and 3.0 mm minimum solder mask clearance. Thermal relief vias under pads are advised for high-reliability thermal management in continuous surge environments.
SMA4F18A Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Package/Case:
- DO-221AC, SMA Flat Leads
- Series:
- SMA4F, TRANSIL™
- 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:
- 39.3V
- Current - Peak Pulse (10/1000µs):
- 13.7A
- Power - Peak Pulse:
- 400W
- Power Line Protection:
- No
- Applications:
- General Purpose
- Capacitance @ Frequency:
- -
- Operating Temperature:
- -55°C ~ 175°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SMAflat
SMA4F18A FAQ
1.How can I place an order for SMA4F18A through Aetrix?
Please submit a Request for Quotation (RFQ) for SMA4F18A 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 SMA4F18A reliable?
The price and inventory of SMA4F18A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMA4F18A is usually 5 days.
3.What payment methods are accepted for SMA4F18A?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMA4F18A transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMA4F18A?
SMA4F18A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMA4F18A 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 SMA4F18A?
For technical support, including SMA4F18A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMA4F18A requirements.
6.How does Aetrix verify that SMA4F18A is sourced from the original manufacturer or authorized distributors?
All SMA4F18A 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 SMA4F18A meets industry standards.
7.What is the process for return or replacement of SMA4F18A?
All SMA4F18A units undergo pre-shipment inspection (PSI). If there is an issue with SMA4F18A, 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 SMA4F18A part is unused and in its original packaging.
Return procedure for SMA4F18A:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SMA4F18A Tags
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