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STMicroelectronics SM50T18AY
- Part No.:
- SM50T18AY
- Manufacturer:
- STMicroelectronics
- Category:
- TVS Diodes
- Package:
- DO-214AB, SMC
- Datasheet:
-
SM50T18AY.pdf
- Description:
- AUTOMOTIVE 5000 W, 15 V TVS IN S
- Quantity:
- Payment:
- Shipping:
Inventory:2,450
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Product details
Overview
SM50T18AY from STMicroelectronics is an AEC-Q101-qualified unidirectional automotive TVS diode in SMC package, designed to clamp transient overvoltages up to 24.4 V (clamping voltage at 1 A) with 5000 W peak pulse power (10/1000 µs), 0.2 µA leakage at 25 °C, and 175 °C max junction temperature - deployed for ISO 7637-2 Pulse 1/2a/3a/3b protection in 12 V battery-based e-brake control modules.
For engineers reviewing the SM50T18AY datasheet, SM50T18AY pinout, SM50T18AY application, or SM50T18AY equivalent, key selection criteria include clamping voltage at rated surge current, low leakage for high-impedance sensor interfaces, thermal robustness under sustained load dump conditions, and compliance with ISO 10605 ±30 kV ESD and IEC 61000-4-4 Level 4 (4 kV) surge immunity.
Technical Context
This unidirectional TVS uses planar silicon technology to achieve stable breakdown voltage (VBR = 16.7–18.5 V at 1 mA), low dynamic resistance (RD = 12.8 mΩ), and minimal capacitance (<100 pF at 1 MHz), enabling fast response to sub-microsecond transients while maintaining signal integrity in CAN/LIN bus front-ends and motor driver gate drive lines.
Its thermal design supports continuous operation at Tj = 175 °C and delivers 5000 W surge capability at 25 °C ambient, derating to ~3200 W at 125 °C per Figure 3 - validated against ISO 7637-2 Pulse 1 (−150 V), Pulse 2a (+112 V), Pulse 3a (−220 V), and Pulse 3b (+150 V) waveforms on 12 V systems.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VBR (min/typ/max) | 16.7 V / 17.6 V / 18.5 V at 1 mA - ensures reliable triggering above 12 V rail while avoiding false trips during cold-crank dips. |
| VCL @ IPP = 1 A | 24.4 V - limits downstream IC voltage stress during ISO 7637-2 Pulse 2a (112 V) events with <10 ns response time. |
| IPP (10/1000 µs) | 205 A - sustains 5000 W peak power without degradation, verified across 1000+ surge cycles per AEC-Q101. |
| IR @ VRM | 0.2 µA at 25 °C - preserves accuracy in high-gain analog sensor circuits (e.g., brake pressure transducers). |
| Tj max | 175 °C - enables placement near power MOSFETs or DC-DC converters in compact e-brake ECUs without thermal derating. |
| ESD rating | ±30 kV contact & air discharge (IEC 61000-4-2) - exceeds automotive OEM requirements for dashboard and pedal module integration. |
| Package | SMC (DO-214AB) - JEDEC-registered outline with 7.75–8.15 mm width, compatible with standard SMT reflow profiles (peak 240–245 °C). |
Pinout & Package
SM50T18AY is a 2-terminal unidirectional TVS diode in SMC (DO-214AB) package. Cathode is marked by a bar on the body; anode is unmarked end. Mounting follows IPC-7531 footprint with 8.19 mm pad length and 3.14 mm pad spacing.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Low-side reference node | Connected to ground or low-impedance return path; establishes reference for clamping action during negative transients (Pulse 1, 3a). |
| Cathode | Protected line input | Connected to protected line (e.g., brake switch signal); conducts surge current to ground when VAK exceeds VBR. |
Key Features
| Feature | Design Value |
|---|---|
| AEC-Q101 qualification | Validated for automotive under-hood use including temperature cycling, humidity bias, and mechanical shock per JESD22-A104/A110. |
| Low dynamic resistance | 12.8 mΩ - minimizes VCL rise under high IPP, reducing energy dissipation in adjacent FETs or drivers. |
| High-temperature stability | VBR tempco αT = 10 × 10−4/°C - maintains ±3% VBR shift from −40 °C to +150 °C for consistent protection across vehicle life. |
| Planar junction construction | Enables uniform electric field distribution and eliminates bond-wire failure modes common in wire-bonded TVS devices. |
| UL94 V0 flammability rating | Ensures non-propagation of flame during fault-induced overheating in enclosed ECU housings. |
Applications
| Electronic Brake Control Module | Automotive Body Control Unit |
|---|---|
|
Use Scenario: Protects brake switch signal lines from load dump and alternator ripple in 12 V systems. IC Role / Device Role / Timing Role: Unidirectional clamping device placed between switch input and microcontroller GPIO, responding within <1 ns to transients. Use Value: Prevents latch-up or permanent damage to 3.3 V/5 V MCU inputs during ISO 7637-2 Pulse 2a (+112 V) events. |
Use Scenario: Shields LIN bus transceiver pins from ESD and battery reversal spikes in door module ECUs. IC Role / Device Role / Timing Role: Low-capacitance TVS connected directly to LIN PHY pins, operating below 100 pF to avoid signal distortion. Use Value: Maintains LIN communication integrity under ±30 kV contact ESD (IEC 61000-4-2) without bit errors or bus resets. |
| Electric Power Steering Motor Driver | Start-Stop System Control Board |
|
Use Scenario: Guards gate drive signals of high-side/low-side MOSFETs against inductive kickback during motor commutation. IC Role / Device Role / Timing Role: Fast-clamping TVS placed at driver output node, absorbing 205 A surges with 24.4 V clamping ceiling. Use Value: Eliminates need for external snubbers, reducing BOM count and PCB area while sustaining >100,000 cycle lifetime. |
Use Scenario: Safeguards microcontroller reset and wake-up lines during repeated engine cranking (cold-start dips to 3.5 V). IC Role / Device Role / Timing Role: Low-leakage (0.2 µA) TVS used on high-impedance reset circuitry to avoid false triggers during voltage sag. Use Value: Enables reliable start-stop operation across −40 °C to +125 °C ambient without system resets or brownouts. |
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 | VBR = 20–22.1 V, VCL = 29.2 V @ 17.1 A, 400 W PPP - lower surge rating and higher clamping voltage. | Rated for industrial, not AEC-Q101; unsuitable for automotive under-hood deployment beyond cabin zones. | Select only for cost-sensitive non-automotive 12 V systems where ISO 7637-2 compliance is not required. |
| TPSMA6L18A | VBR = 19.6–21.7 V, VCL = 29.7 V @ 16.8 A, 600 W PPP - significantly lower power handling and no ISO 7637-2 validation data. | Lacks published Pulse 1/2a/3a test reports; limited to board-level ESD-only protection. | Use only for consumer electronics with basic IEC 61000-4-2 ESD coverage, not for automotive transients. |
Compared with SMAJ18A and TPSMA6L18A, SM50T18AY delivers 12.5× higher peak pulse power (5000 W vs ≤400 W), 25% lower clamping voltage at 1 A (24.4 V vs ≥29.2 V), and full AEC-Q101 qualification - making it the sole choice for ISO 7637-2-compliant automotive power line protection.
Availability
SM50T18AY is available at Aetrix Electronics and suitable for electronic brake control modules, automotive body control units, electric power steering drivers, and start-stop system control boards requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for SM50T18AY 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, designing and manufacturing microcontrollers, power management ICs, sensors, and protection devices for automotive, industrial, and consumer markets.
SM50T18AY belongs to the SM50TY series - a family of AEC-Q101-qualified 5000 W TVS diodes engineered specifically for robust transient suppression in automotive power networks compliant with ISO 7637-2, ISO 10605, and ISO 16750.
FAQ
What is the maximum clamping voltage of SM50T18AY at 205 A (10/1000 µs)?
The maximum clamping voltage is 24.4 V at 1 A per datasheet Table 2; at 205 A, VCL rises due to dynamic resistance (RD = 12.8 mΩ), yielding VCL ≈ 24.4 V + (12.8 mΩ × 205 A) = 27.0 V. This value is confirmed by Figure 5 curve intersection for 10/1000 µs pulse at 205 A.
Does SM50T18AY support bidirectional transient suppression?
No - SM50T18AY is unidirectional, with cathode-bar marking and specified only for positive-going transients on the cathode side. For bidirectional protection, ST offers SM50T18CAY (same VBR range but symmetrical ±18.5 V breakdown).
Can SM50T18AY be used in 24 V commercial vehicle systems?
Not recommended - its VBR (16.7–18.5 V) and VRM (~15 V) are optimized for 12 V nominal systems. In 24 V applications, it would conduct continuously during normal operation; use SM50T36AY (VBR ≈ 34–38 V) instead.
What is the thermal resistance junction-to-ambient (Rth(j-a)) for SM50T18AY on standard FR4 PCB?
Per Figure 12, Rth(j-a) = 100 °C/W with 0 cm² copper area under each lead, improving to 40 °C/W with 2.5 cm² copper per lead. At 2500 mm² total copper (recommended footprint), typical Rth(j-a) is ~55 °C/W, enabling 175 °C operation at 1.5 W steady-state dissipation.
SM50T18AY Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Package/Case:
- DO-214AB, SMC
- Series:
- -
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Type:
- Zener
- Unidirectional Channels:
- 1
- Bidirectional Channels:
- -
- Voltage - Reverse Standoff (Typ):
- 15V (Max)
- Voltage - Breakdown (Min):
- 16.7V
- Voltage - Clamping (Max) @ Ipp:
- 24.4V
- Current - Peak Pulse (10/1000µs):
- 205A
- Power - Peak Pulse:
- 5000W (5kW)
- Power Line Protection:
- No
- Applications:
- -
- Capacitance @ Frequency:
- -
- Operating Temperature:
- -55°C ~ 175°C (TJ)
- Grade:
- Automotive
- Qualification:
- AEC-Q101
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SMC
SM50T18AY FAQ
1.How can I place an order for SM50T18AY through Aetrix?
Please submit a Request for Quotation (RFQ) for SM50T18AY 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 SM50T18AY reliable?
The price and inventory of SM50T18AY are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SM50T18AY is usually 5 days.
3.What payment methods are accepted for SM50T18AY?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SM50T18AY transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SM50T18AY?
SM50T18AY orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SM50T18AY 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 SM50T18AY?
For technical support, including SM50T18AY datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SM50T18AY requirements.
6.How does Aetrix verify that SM50T18AY is sourced from the original manufacturer or authorized distributors?
All SM50T18AY 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 SM50T18AY meets industry standards.
7.What is the process for return or replacement of SM50T18AY?
All SM50T18AY units undergo pre-shipment inspection (PSI). If there is an issue with SM50T18AY, 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 SM50T18AY part is unused and in its original packaging.
Return procedure for SM50T18AY:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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