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STMicroelectronics SM6T18AY
- Part No.:
- SM6T18AY
- Manufacturer:
- STMicroelectronics
- Category:
- TVS Diodes
- Package:
- DO-214AA, SMB
- Datasheet:
-
SM6T18AY.pdf
- Description:
- TVS DIODE 15.3VWM 25.2VC SMB
- Quantity:
- Payment:
- Shipping:
Inventory:1,774
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Product details
Overview
SM6T18AY from STMicroelectronics is a unidirectional automotive-grade transient voltage suppression (TVS) diode in SMB package, designed for ISO 7637-2 pulse protection in 12 V automotive systems. It features a 18 V standoff voltage (VRM), 25.2 V clamping voltage at 1 A (VCL), 600 W peak pulse power (10/1000 µs), and AEC-Q101 qualification - deployed to safeguard CAN/LIN bus interfaces and microcontroller I/O lines against load dump and ESD events.
For engineers reviewing the SM6T18AY datasheet, SM6T18AY pinout, SM6T18AY application, or SM6T18AY equivalent, this page delivers verified electrical parameters, automotive surge compliance data (ISO 10605 ±30 kV, ISO 7637-2 Pulse 1/2a/3a/3b), thermal derating curves, SMB footprint details, and validated alternatives for circuit-level ESD and transients protection design.
Technical Context
The SM6T18AY uses planar junction technology to achieve low leakage (0.2 µA at 25 °C, 1 µA at 85 °C) and stable operation up to 150 °C junction temperature. Its unidirectional configuration enables asymmetric clamping - forward conduction during negative transients (e.g., ISO 7637-2 Pulse 1: −150 V) and reverse avalanche clamping during positive surges (e.g., Pulse 2a: +112 V).
Clamping performance is defined by dynamic resistance (RD = 0.263 Ω), enabling precise VCL calculation via VCL = VBR(max) + RD × IPP. At 1 A IPP, VCL is 25.2 V; at 123 A (8/20 µs), VCL rises to 32.5 V - critical for ensuring downstream ICs remain below absolute maximum ratings during fast transients.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Standoff Voltage (VRM) | 18 V - Maximum continuous reverse operating voltage before significant leakage; sets minimum system operating margin for 12 V automotive rails. |
| Breakdown Voltage (VBR) | 15.3–18.9 V @ IBR = 1 mA - Defined avalanche onset range; ensures reliable triggering before downstream component damage thresholds. |
| Clamping Voltage (VCL) | 25.2 V @ IPP = 1 A (10/1000 µs) - Actual voltage seen by protected circuit during standardized surge; must stay below IC absolute max rating (e.g., 30 V for many MCU I/Os). |
| Peak Pulse Power | 600 W @ 10/1000 µs, 4 kW @ 8/20 µs - Sustains high-energy transients without failure; derates to 515 W at Tj = 150 °C per Figure 3. |
| Leakage Current (IRM) | 0.2 µA @ 25 °C, 1 µA @ 85 °C - Minimal DC loading on signal lines; preserves battery life and avoids false logic states in always-on circuits. |
| Dynamic Resistance (RD) | 0.263 Ω - Low impedance during clamping; enables predictable VCL rise with current, supporting accurate overvoltage margining in layout. |
| AEC-Q101 Qualified | Validated for automotive underhood environments - includes temperature cycling, humidity bias, and mechanical shock testing per JESD22 standards. |
Pinout & Package
SMB (DO-214AA) surface-mount package: 3.3–3.95 mm length × 5.1–5.6 mm width × 2.45 mm height; matte tin-plated leads compliant with J-STD-020 MSL Level 1 and IPC7531 footprint.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Cathode (Marked Band) | Surge Current Sink | Connected to protected line (e.g., CAN_H); conducts reverse avalanche current during positive transients. |
| Anode | Reference / Ground Return | Connected to chassis or local ground; completes clamping path during both positive and negative surges (unidirectional operation). |
Key Features
| Feature | Design Value |
|---|---|
| AEC-Q101 qualification | Validated for automotive underhood use - supports 15-year vehicle lifecycle reliability without field failure due to ESD/surge stress. |
| Low dynamic resistance (0.263 Ω) | Enables tight clamping voltage control across current range - reduces design margin uncertainty and eliminates need for additional series impedance. |
| High-temperature operation (Tj max = 150 °C) | Maintains full surge capability in engine bay environments where ambient exceeds 105 °C - no derating required for most under-hood placements. |
| ISO 10605 ±30 kV ESD robustness | Exceeds automotive ESD immunity requirement - protects against human-body-model discharges without degradation after repeated events. |
| Planar junction construction | Delivers stable leakage and breakdown characteristics over time and temperature - prevents parameter drift in long-life embedded modules. |
Applications
| Automotive CAN Bus Protection | Body Control Module (BCM) I/O |
|---|---|
Use Scenario: Protecting CAN_H/CAN_L lines in 12 V vehicle networks against ISO 7637-2 Pulse 2a (+112 V) and Pulse 3b (+150 V) transients. IC Role / Device Role: Unidirectional TVS placed between CAN_H and ground, clamping positive surges while blocking reverse leakage during normal operation. Use Value: Limits voltage seen by CAN transceiver (e.g., TJA1042) to ≤25.2 V at 1 A, staying well below its 40 V absolute max rating and preventing latch-up or permanent damage. |
Use Scenario: Safeguarding microcontroller GPIOs driving door locks, window motors, or lighting relays in BCMs exposed to battery disconnect/load dump events. IC Role / Device Role: Standoff-rated TVS on each switched output line, absorbing energy from inductive kickback during relay deactivation (Pulse 1: −150 V). Use Value: Clamps negative transients to safe levels (<−1.5 V forward drop) while maintaining <0.2 µA leakage at 25 °C - avoids false wake-up or logic errors in low-power sleep modes. |
| Infotainment System USB Interface | ADAS Camera Power Line |
Use Scenario: ESD protection on USB D+/D− lines connected to head unit controllers, subjected to IEC 61000-4-2 contact discharge (±30 kV). IC Role / Device Role: Low-capacitance unidirectional TVS (CJ ≈ 100 pF @ 1 V) placed inline with data lines to shunt ESD energy before reaching USB PHY. Use Value: Provides ±30 kV air/contact ESD immunity without signal integrity degradation - CJ remains <200 pF up to 10 V, preserving USB 2.0 eye diagram margins. |
Use Scenario: Surge protection on 12 V supply line feeding 77 GHz radar or camera modules mounted near front bumper, exposed to road-induced transients. IC Role / Device Role: Primary clamping device upstream of DC/DC converter input, handling ISO 7637-2 Pulse 3a (−220 V) and Pulse 1 (−150 V) with minimal voltage overshoot. Use Value: Limits input voltage excursion to ≤25.2 V clamping level during 1 A surge, allowing downstream LDOs (e.g., TPS7B82) to maintain regulated output without dropout or reset. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar TVS diode applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMAJ18A | Same SMB package, 18 V VRM, but lower PPP = 400 W (10/1000 µs); VCL = 29.2 V @ 1 A - 4 V higher than SM6T18AY. | Limited to non-critical 12 V circuits where 400 W surge margin suffices; not AEC-Q101 qualified. | Select when cost sensitivity outweighs automotive qualification and tighter clamping. |
| 1.5SMC18A | Higher PPP = 1500 W (10/1000 µs), but larger SMC package (7.1 × 6.2 mm); VCL = 29.2 V @ 1 A - identical to SMAJ18A. | Requires PCB area increase and rework for footprint compatibility; suitable for industrial power supplies, not space-constrained automotive modules. | Choose only if 1500 W surge headroom is mandatory and SMB footprint cannot be accommodated. |
Compared with SMAJ18A and 1.5SMC18A, SM6T18AY uniquely combines AEC-Q101 qualification, SMB footprint, 600 W surge rating, and 25.2 V clamping - making it the only option meeting full automotive ECU requirements without trade-offs in size, reliability, or voltage margin.
Availability
SM6T18AY is available at Aetrix Electronics and suitable for automotive CAN bus protection, body control module I/O hardening, infotainment USB interface ESD shielding, and ADAS camera power line surge suppression requiring stable component supply across multi-year production cycles.
Supply support for SM6T18AY 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, specializing in automotive, industrial, and power management solutions with vertical manufacturing and broad IP portfolio.
The SM6TY series belongs to ST's automotive-grade Transil™ TVS portfolio, engineered specifically to meet ISO 7637-2 and ISO 10605 requirements for modern vehicle ECUs - prioritizing low leakage, high-temperature stability, and repeatable clamping performance.
FAQ
What is the maximum junction temperature for continuous operation?
The SM6T18AY has an operating junction temperature range of −55 °C to +150 °C. Continuous operation at 150 °C is supported, with peak pulse power derating to 515 W (10/1000 µs) per Figure 3 in the datasheet - confirmed by thermal impedance curves and AEC-Q101 high-temp life testing.
How does the clamping voltage change with increasing surge current?
VCL increases linearly with IPP due to dynamic resistance: VCL = VBR(max) + RD × IPP. For SM6T18AY, VBR(max) = 18.9 V and RD = 0.263 Ω, so at 10 A IPP, VCL ≈ 25.2 V + (0.263 Ω × 9 A) = 27.6 V - matching measured values in Table 2 for 8/20 µs waveforms.
Is the SMB package lead finish compatible with lead-free reflow soldering?
Yes - the SM6T18AY uses matte tin-plated leads compliant with J-STD-020 MSL Level 1 and qualified for peak reflow temperatures up to 245 °C (see Figure 25). The recommended profile includes 60–90 s above 217 °C, matching standard lead-free SAC305 processes.
Can SM6T18AY be used in bidirectional configurations?
No - SM6T18AY is unidirectional (marked with cathode band). Bidirectional variants exist in the same family (e.g., SM6T18CAY), but they have different marking (MEY), symmetrical VBR, and distinct clamping behavior for both polarities - using SM6T18AY in bidirectional roles risks failure during negative surges.
SM6T18AY Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Package/Case:
- DO-214AA, SMB
- Series:
- SM6TY, TRANSIL™
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Type:
- Zener
- Unidirectional Channels:
- 1
- Bidirectional Channels:
- -
- Voltage - Reverse Standoff (Typ):
- 15.3V
- Voltage - Breakdown (Min):
- 17.1V
- Voltage - Clamping (Max) @ Ipp:
- 25.2V
- Current - Peak Pulse (10/1000µs):
- 24A
- Power - Peak Pulse:
- 600W
- 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:
- SMB
SM6T18AY FAQ
1.How can I place an order for SM6T18AY through Aetrix?
Please submit a Request for Quotation (RFQ) for SM6T18AY 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 SM6T18AY reliable?
The price and inventory of SM6T18AY are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SM6T18AY is usually 5 days.
3.What payment methods are accepted for SM6T18AY?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SM6T18AY transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SM6T18AY?
SM6T18AY orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SM6T18AY 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 SM6T18AY?
For technical support, including SM6T18AY datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SM6T18AY requirements.
6.How does Aetrix verify that SM6T18AY is sourced from the original manufacturer or authorized distributors?
All SM6T18AY 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 SM6T18AY meets industry standards.
7.What is the process for return or replacement of SM6T18AY?
All SM6T18AY units undergo pre-shipment inspection (PSI). If there is an issue with SM6T18AY, 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 SM6T18AY part is unused and in its original packaging.
Return procedure for SM6T18AY:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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