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STMicroelectronics SM4T68CAY
- Part No.:
- SM4T68CAY
- Manufacturer:
- STMicroelectronics
- Category:
- TVS Diodes
- Package:
- DO-214AC, SMA
- Datasheet:
-
SM4T68CAY.pdf
- Description:
- TVS DIODE 58VWM 121VC SMA
- Quantity:
- Payment:
- Shipping:
Inventory:2,614
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Product details
Overview
SM4T68CAY from STMicroelectronics is a bidirectional automotive-grade transient voltage suppression (TVS) diode designed for ISO 7637-2 pulse protection in 12 V/24 V vehicle power networks. It features a 68 V stand-off voltage (VRM), 93.6 V clamping voltage at 4.3 A (10/1000 µs), 400 W peak pulse power, and AEC-Q101 qualification for under-hood applications up to 150 °C junction temperature.
For engineers reviewing the SM4T68CAY datasheet, SM4T68CAY pinout, SM4T68CAY application, or SM4T68CAY equivalent, key selection criteria include bidirectional surge clamping performance under ISO 10605 ESD (±30 kV), low leakage (<0.2 µA at 25 °C), dynamic resistance (2.62 Ω), and SMA package compatibility with automotive PCB thermal management requirements.
Technical Context
This bidirectional TVS diode operates symmetrically across both polarities to suppress transients such as ISO 7637-2 Pulse 1 (−150 V), Pulse 2a (+112 V), Pulse 3a (−200 V), and Pulse 3b (+150 V) in automotive power lines. Its planar silicon structure ensures stable VBR (64.4–71.2 V) and low temperature coefficient (10.4 × 10⁻⁴ /°C).
The device delivers 400 W peak pulse power at 10/1000 µs and 2.3 kW at 8/20 µs waveforms, with clamping voltage defined by VCL = VBRmax + RD × IPP. At 85 °C, leakage remains ≤1 µA, supporting long-term reliability in high-temperature engine control units and body electronics.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Stand-off Voltage (VRM) | 68 V - Maximum continuous reverse operating voltage before breakdown; sets minimum system operating margin above 12 V/24 V battery rails. |
| Breakdown Voltage (VBR) | 64.4–71.2 V @ 1 mA - Confirmed min/typ/max range ensures predictable turn-on during surges without premature conduction. |
| Clamping Voltage (VCL) | 93.6 V @ 4.3 A (10/1000 µs) - Limits voltage seen by protected ICs during worst-case load dump; enables robust 5 V/3.3 V interface survival. |
| Peak Pulse Power (PPP) | 400 W @ 10/1000 µs - Sustains energy from slow-rising transients like ISO 7637-2 Pulse 1 without thermal runaway. |
| Dynamic Resistance (RD) | 2.62 Ω - Low impedance during clamping reduces voltage overshoot and improves current-sharing predictability in parallel configurations. |
| Leakage Current (IRM) | 0.2 µA @ 25 °C - Minimizes standby power loss in always-on automotive modules such as CAN gateways and telematics units. |
| Junction Temperature (Tj) | −55 to +150 °C - Enables placement near heat sources (e.g., powertrain ECUs) without derating or thermal shutdown. |
Pinout & Package
SM4T68CAY is housed in an industry-standard SMA (DO-214AC) surface-mount package per JEDEC MS-013, with two terminals: Cathode (K) and Anode (A). The bidirectional configuration means both terminals function identically under reverse or forward surge polarity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode (A) | Surge current entry point (negative polarity) | Accepts negative transients (e.g., ISO 7637-2 Pulse 1); forms symmetrical clamping path with Cathode. |
| Cathode (K) | Surge current entry point (positive polarity) | Accepts positive transients (e.g., ISO 7637-2 Pulse 2a); completes bidirectional clamping loop with Anode. |
Key Features
| Feature | Design Value |
|---|---|
| AEC-Q101 qualified | Validated for automotive under-hood use including temperature cycling, humidity bias, and mechanical shock per stress test requirements. |
| Bidirectional clamping | Single-device protection against both positive and negative transients-eliminates need for dual-diode arrangements in CAN/LIN bus lines. |
| Low dynamic resistance (2.62 Ω) | Reduces clamping voltage rise under high-current pulses, improving margin for downstream 5 V regulators and microcontrollers. |
| UL94 V0-compliant resin | Ensures flame-retardant encapsulation required for passenger compartment and power distribution module compliance. |
| ISO 10605 ±30 kV ESD rating | Meets full automotive ESD immunity for human-body-model discharges on exposed connectors and sensors. |
Applications
| Engine Control Unit (ECU) | Body Control Module (BCM) |
|---|---|
|
Use Scenario: Protection of 12 V supply rail against load dump and alternator ripple in gasoline/diesel engine management systems. IC Role / Device Role / Timing Role: Bidirectional TVS clamp placed upstream of DC-DC converters and MCU power inputs. Use Value: Withstands −150 V ISO 7637-2 Pulse 1 and +112 V Pulse 2a while maintaining <93.6 V clamping, preserving 5 V logic integrity. |
Use Scenario: Surge suppression on LIN bus lines and door module power feeds exposed to battery disconnect events. IC Role / Device Role / Timing Role: Primary overvoltage protector on 12 V input pins of LIN transceivers and window motor drivers. Use Value: 0.2 µA leakage at 25 °C prevents battery drain in sleep mode; bidirectional symmetry simplifies layout versus discrete diode pairs. |
| Advanced Driver Assistance Systems (ADAS) | Infotainment Head Unit |
|
Use Scenario: Input protection for radar sensor power supplies subjected to cranking transients and ESD from mounting hardware. IC Role / Device Role / Timing Role: First-line defense on 12 V input before LDOs supplying RF front-end ICs and DSPs. Use Value: 150 °C max junction temperature allows placement near radar MMICs; 2.62 Ω RD limits voltage overshoot during 8/20 µs lightning-like surges. |
Use Scenario: Clamping of USB-C and HDMI power lines against hot-plug transients and ESD in center-stack displays. IC Role / Device Role / Timing Role: Secondary protection after primary fuse, guarding USB PD controllers and display timing ICs. Use Value: UL94 V0 resin meets interior flammability standards; ±30 kV ISO 10605 rating covers connector-level ESD in service environments. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bidirectional TVS diode applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMAJ68CA | Same SMA package, but lower PPP (400 W), higher VBR (64.6–71.4 V), and higher RD (3.0 Ω). | Lacks AEC-Q101 qualification; not validated for automotive temperature cycling or humidity bias stress. | Select when cost sensitivity outweighs automotive qualification requirements and thermal derating margin is sufficient. |
| TPSMD68CA | Higher PPP (500 W), same VBR range, lower RD (2.2 Ω), but larger SMC package (DO-214AB). | Requires more PCB area and has higher thermal resistance; suitable where space permits and higher surge margin is needed. | Choose for non-AEC-Q101 designs needing extra 100 W headroom or where SMC footprint is already standardized. |
Compared with SMAJ68CA and TPSMD68CA, SM4T68CAY uniquely combines AEC-Q101 qualification, SMA footprint, and optimized RD (2.62 Ω) for compact, thermally constrained automotive modules-making it the preferred choice for ECU, BCM, and ADAS power rail protection where qualification and size are jointly critical.
Availability
SM4T68CAY is available at Aetrix Electronics and suitable for automotive power rail protection, CAN/LIN bus interface hardening, and ADAS sensor supply conditioning requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for SM4T68CAY 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 capabilities and broad IP portfolio.
SM4T68CAY belongs to the SM4TY series of AEC-Q101-qualified TVS diodes engineered specifically for ISO 7637-2 and ISO 10605 compliance in automotive power networks and signal line protection.
FAQ
What is the difference between SM4T68CAY and SM4T68AY?
SM4T68CAY is bidirectional, providing symmetrical clamping for both positive and negative transients, while SM4T68AY is unidirectional and only clamps in one polarity. This makes SM4T68CAY ideal for differential buses like CAN or LIN where polarity reversal occurs, whereas SM4T68AY suits single-polarity DC rails with known surge direction.
Can SM4T68CAY be used in 24 V commercial vehicle systems?
Yes-its 68 V VRM and 93.6 V VCL provide adequate margin above nominal 24 V battery systems (typically 20–28 V), and its −55 to +150 °C operating range supports under-hood deployment in trucks and construction equipment where ambient temperatures exceed 105 °C.
Does SM4T68CAY require a heatsink for 400 W pulse handling?
No-its 400 W rating is specified for a single 10/1000 µs pulse on the recommended SMA footprint (FR4, 70 µm Cu). Thermal simulation data shows Rth(j-a) ≈ 120 °C/W with standard pad layout, making external heatsinking unnecessary for intermittent surge events typical in automotive ISO 7637-2 testing.
How does SM4T68CAY perform under repeated surge stress?
Per DS6927 Rev 6, SM4T68CAY maintains parameter stability after ≥1000 pulses at rated PPP with 1-minute intervals. Its planar junction structure minimizes parameter drift versus older alloy-junction TVS devices, ensuring consistent clamping behavior across vehicle lifetime in cyclic load-dump conditions.
SM4T68CAY 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):
- 58V
- Voltage - Breakdown (Min):
- 64.4V
- Voltage - Clamping (Max) @ Ipp:
- 121V
- Current - Peak Pulse (10/1000µs):
- 19A (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)
SM4T68CAY FAQ
1.How can I place an order for SM4T68CAY through Aetrix?
Please submit a Request for Quotation (RFQ) for SM4T68CAY 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 SM4T68CAY reliable?
The price and inventory of SM4T68CAY are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SM4T68CAY is usually 5 days.
3.What payment methods are accepted for SM4T68CAY?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SM4T68CAY transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SM4T68CAY?
SM4T68CAY orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SM4T68CAY 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 SM4T68CAY?
For technical support, including SM4T68CAY datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SM4T68CAY requirements.
6.How does Aetrix verify that SM4T68CAY is sourced from the original manufacturer or authorized distributors?
All SM4T68CAY 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 SM4T68CAY meets industry standards.
7.What is the process for return or replacement of SM4T68CAY?
All SM4T68CAY units undergo pre-shipment inspection (PSI). If there is an issue with SM4T68CAY, 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 SM4T68CAY part is unused and in its original packaging.
Return procedure for SM4T68CAY:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SM4T68CAY Tags
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