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STMicroelectronics SM4T18CAY
- Part No.:
- SM4T18CAY
- Manufacturer:
- STMicroelectronics
- Category:
- TVS Diodes
- Package:
- DO-214AC, SMA
- Datasheet:
-
SM4T18CAY.pdf
- Description:
- TVS DIODE 15VWM 32.5VC SMA
- Quantity:
- Payment:
- Shipping:
Inventory:9,294
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Product details
Overview
SM4T18CAY from STMicroelectronics is a bidirectional automotive-grade transient voltage suppression (TVS) diode designed for ISO 7637-2 pulse protection in 12 V vehicle power networks. It features a 17.6 V nominal breakdown voltage (VBR), 24.4 V clamping voltage (VCL) at 16.4 A (10/1000 µs), 400 W peak pulse power, and AEC-Q101 qualification for under-hood reliability.
For engineers reviewing the SM4T18CAY datasheet, SM4T18CAY pinout, SM4T18CAY application, or SM4T18CAY equivalent, this device serves as a robust, low-leakage (≤1 µA @ 85 °C), high-junction-temperature (Tj max = 150 °C) surge protector for CAN, LIN, and sensor supply lines exposed to load dump, inductive switching, and ESD per ISO 10605.
Technical Context
The SM4T18CAY implements planar junction technology to achieve low dynamic resistance (RD = 0.361 Ω) and stable VBR temperature coefficient (αT = 8.8 × 10−4/°C), enabling predictable clamping across −55 °C to +150 °C operating range. Its bidirectional configuration supports symmetrical surge suppression on differential or floating signal lines without polarity constraints.
It meets stringent automotive immunity standards: ±30 kV ESD (ISO 10605, both C = 150 pF & 330 pF), and ISO 7637-2 pulses including Pulse 1 (−150 V), Pulse 2a (+112 V), Pulse 3a (−200 V), and Pulse 3b (+150 V) - all validated at Tj = 150 °C with JEDEC-registered SMA package thermal performance.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VBR (min/typ/max) | 16.7 / 17.6 / 18.5 V @ IBR = 1 mA - ensures reliable turn-on before system overvoltage damages downstream ICs |
| VCL @ 16.4 A (10/1000 µs) | 24.4 V - limits transient voltage seen by protected circuit during 400 W surge events |
| IPP (8/20 µs) | 32.5 A - supports high-energy transients like load dump with 2.3 kW capability |
| RD (dynamic resistance) | 0.361 Ω - minimizes voltage overshoot during fast-rising surges (e.g., ESD) |
| IR @ VRM = 15 V | 0.2 µA @ 25 °C / 1 µA @ 85 °C - prevents leakage-induced bias shift in high-impedance sensor interfaces |
| Tj operating range | −55 °C to +150 °C - enables placement near engines or power electronics without derating |
| AEC-Q101 qualified | Validated for automotive use per stress test conditions including HTOL, TC, and HAST |
Pinout & Package
SM4T18CAY uses the industry-standard SMA (DO-214AC) surface-mount package per IPC 7531, with JEDEC-registered outline and UL94 V0-compliant resin. The bidirectional structure has no anode/cathode designation - both terminals are functionally symmetric.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode (Cathode) | Surge current path (bidirectional) | Both terminals conduct equally during positive or negative transients - no polarity sensitivity in layout |
| Cathode (Anode) | Surge current path (bidirectional) | Enables single-device protection of AC-coupled or floating lines (e.g., CAN_H/CAN_L pair) |
Key Features
| Feature | Design Value |
|---|---|
| Bidirectional surge suppression | Protects differential buses (CAN, LIN) without requiring dual unidirectional devices or polarity-aware routing |
| Low dynamic resistance (0.361 Ω) | Reduces clamping voltage overshoot during sub-microsecond ESD events, improving margin for 3.3 V/5 V logic |
| AEC-Q101 qualification | Guarantees reliability for automotive powertrain, body control, and ADAS modules with zero infant mortality screening waivers |
| 150 °C junction temperature rating | Supports direct mounting on high-power PCB traces or near DC-DC converters without thermal derating |
| UL94 V0 resin housing | Meets flammability requirements for engine bay and cabin-mounted ECUs per ISO 26262 functional safety compliance |
Applications
| Automotive CAN Bus Protection | Engine Control Unit (ECU) Power Input |
|---|---|
|
Use Scenario: Protecting CAN_H/CAN_L differential pair against coupled transients from alternator load dump and relay switching noise. IC Role / Device Role / Timing Role: Bidirectional TVS clamp placed directly at connector entry point to limit common-mode surge voltage to <24.4 V. Use Value: Prevents CAN transceiver latch-up or damage while maintaining bus integrity during ISO 7637-2 Pulse 1 (−150 V) and Pulse 3b (+150 V) events. |
Use Scenario: Safeguarding 12 V input rail of engine control units exposed to battery disconnection spikes and inductive kickback. IC Role / Device Role / Timing Role: Primary front-end surge suppressor mounted upstream of DC-DC converter input filter. Use Value: Clamps 400 W (10/1000 µs) transients to ≤24.4 V, preserving input capacitor lifetime and preventing regulator shutdown. |
| Body Control Module (BCM) Sensor Inputs | Automotive LIN Bus Node |
|
Use Scenario: Shielding analog sensor inputs (e.g., temperature, pressure) from ESD and cable discharge events in door modules and lighting systems. IC Role / Device Role / Timing Role: Low-leakage (0.2 µA @ 25 °C) TVS placed adjacent to ADC input pins to avoid signal offset drift. Use Value: Maintains sensor accuracy over full temperature range while passing ±30 kV contact discharge per ISO 10605. |
Use Scenario: Protecting LIN transceiver I/O against electrostatic discharge during assembly and service operations. IC Role / Device Role / Timing Role: Bidirectional clamp integrated into LIN header footprint to suppress both polarities of ESD without adding board area. Use Value: Enables single-device protection of LIN bus with <24.4 V clamping, ensuring transceiver survival during 15 kV air discharge events. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bidirectional TVS diode applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMAJ18CA | Higher VCL = 29.2 V @ 13.7 A (10/1000 µs); lower PPP = 400 W but higher RD = 0.514 Ω | Limited to less demanding ESD environments due to 5 V higher clamping voltage | Choose when cost is prioritized over clamping tightness and thermal margin is ample |
| 1.5SMC18CA | Same VBR range but SMC package (larger footprint); VCL = 27.7 V @ 14.4 A; Tj max = 175 °C | Requires more PCB area; better suited for under-hood power distribution vs. space-constrained modules | Prefer for high-volume power rail protection where thermal mass outweighs size constraints |
Compared with SMAJ18CA and 1.5SMC18CA, SM4T18CAY delivers tighter clamping (24.4 V vs. ≥27.7 V), lower leakage (<1 µA vs. ≥2 µA @ 85 °C), and optimized SMA footprint for dense automotive PCB layouts - making it superior for CAN/LIN nodes and sensor interfaces where voltage margin and board space are critical.
Availability
SM4T18CAY is available at Aetrix Electronics and suitable for automotive electronics design, CAN/LIN bus protection, and engine control unit (ECU) power input conditioning requiring stable component supply across production lifecycles.
Supply support for SM4T18CAY 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 automotive, industrial, and power management solutions with vertical manufacturing and long-term product longevity commitments.
SM4T18CAY belongs to the SM4TY series - a family of AEC-Q101-qualified TVS diodes engineered specifically for ISO 7637-2 and ISO 10605 compliance in automotive electronic control units, body electronics, and ADAS subsystems.
FAQ
Is SM4T18CAY unidirectional or bidirectional?
SM4T18CAY is a bidirectional TVS diode, as indicated by the "C" in its part number suffix. Its symmetrical breakdown behavior protects both positive and negative transients equally, making it ideal for differential buses like CAN and LIN without polarity concerns.
What is the maximum clamping voltage at 32.5 A (8/20 µs)?
The maximum clamping voltage for SM4T18CAY at 32.5 A with an 8/20 µs waveform is 32.5 V, derived from VCL(max) = VBR(max) + RD × IPP = 18.5 V + 0.361 Ω × 32.5 A, matching the datasheet's specified 32.5 V value for this condition.
Can SM4T18CAY replace SM4T18AY in a design?
No - SM4T18AY is unidirectional and only clamps negative transients, whereas SM4T18CAY is bidirectional. Substitution requires verifying circuit topology: unidirectional parts suit grounded-signal rails, while bidirectional parts are mandatory for floating or differential lines like CAN_H/CAN_L.
Does SM4T18CAY require derating above 85 °C ambient?
Yes - although rated for Tj up to 150 °C, its peak pulse power must be derated linearly above Tamb = 85 °C per Figure 3 in DS6927. At 125 °C ambient, maximum PPP drops to ~220 W for 10/1000 µs pulses due to thermal impedance limitations of the SMA package.
SM4T18CAY Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Package/Case:
- DO-214AC, SMA
- Series:
- SM4TY, TRANSIL™
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Type:
- Zener
- Unidirectional Channels:
- -
- Bidirectional Channels:
- 1
- Voltage - Reverse Standoff (Typ):
- 15V
- Voltage - Breakdown (Min):
- 16.7V
- Voltage - Clamping (Max) @ Ipp:
- 32.5V
- Current - Peak Pulse (10/1000µs):
- 71A (8/20µs)
- Power - Peak Pulse:
- 400W
- Power Line Protection:
- No
- Applications:
- -
- Capacitance @ Frequency:
- -
- Operating Temperature:
- -55°C ~ 150°C (TJ)
- Grade:
- Automotive
- Qualification:
- AEC-Q101
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- DO-214AC (SMA)
SM4T18CAY FAQ
1.How can I place an order for SM4T18CAY through Aetrix?
Please submit a Request for Quotation (RFQ) for SM4T18CAY 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 SM4T18CAY reliable?
The price and inventory of SM4T18CAY are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SM4T18CAY is usually 5 days.
3.What payment methods are accepted for SM4T18CAY?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SM4T18CAY transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SM4T18CAY?
SM4T18CAY orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SM4T18CAY 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 SM4T18CAY?
For technical support, including SM4T18CAY datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SM4T18CAY requirements.
6.How does Aetrix verify that SM4T18CAY is sourced from the original manufacturer or authorized distributors?
All SM4T18CAY 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 SM4T18CAY meets industry standards.
7.What is the process for return or replacement of SM4T18CAY?
All SM4T18CAY units undergo pre-shipment inspection (PSI). If there is an issue with SM4T18CAY, 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 SM4T18CAY part is unused and in its original packaging.
Return procedure for SM4T18CAY:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SM4T18CAY Tags
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