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STMicroelectronics SM4T68AY
- Part No.:
- SM4T68AY
- Manufacturer:
- STMicroelectronics
- Category:
- TVS Diodes
- Package:
- DO-214AC, SMA
- Datasheet:
-
SM4T68AY.pdf
- Description:
- TVS DIODE 58VWM 121VC SMA
- Quantity:
- Payment:
- Shipping:
Inventory:19,328
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Product details
Overview
SM4T68AY from STMicroelectronics is a unidirectional automotive-grade transient voltage suppression (TVS) diode in SMA package, designed for ISO 7637-2 pulse protection (Pulse 1: −150 V; Pulse 2a: +112 V; Pulse 3a: −200 V; Pulse 3b: +150 V) and ISO 10605 ESD immunity (±30 kV air/contact). It features a 68 V stand-off voltage (VRM), 93.6 V clamping voltage (VCL) at 4.3 A IPP (10/1000 µs), and operates up to 150 °C junction temperature.
For engineers reviewing the SM4T68AY datasheet, SM4T68AY pinout, SM4T68AY application, or SM4T68AY equivalent, this device is selected for high-reliability 12 V/24 V automotive power line protection where low leakage (<0.2 µA @ 25 °C), AEC-Q101 qualification, and stable clamping under repetitive surge stress are critical design requirements.
Technical Context
The SM4T68AY uses planar silicon technology to achieve low dynamic resistance (RD = 2.62 Ω) and minimal junction capacitance-enabling fast response to transients while maintaining low leakage across −55 °C to +150 °C operating range. Its unidirectional configuration provides asymmetric clamping optimized for DC-biased automotive supply rails.
It complies with ISO 7637-2 (Pulse 1, 2a, 3a, 3b) and ISO 10605 (150 pF/330 Ω and 330 pF/330 Ω) standards, delivering 400 W peak pulse power (10/1000 µs) and 121 A peak pulse current (8/20 µs) with verified clamping stability over temperature via αT = 10.4 × 10⁻⁴ /°C voltage drift coefficient.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Stand-off Voltage (VRM) | 68 V - Maximum continuous reverse operating voltage before breakdown; sets minimum system overvoltage threshold. |
| Breakdown Voltage (VBR) | 64.4–71.2 V @ IBR = 1 mA - Tight 10% tolerance ensures predictable turn-on during surge events. |
| Clamping Voltage (VCL) | 93.6 V @ IPP = 4.3 A (10/1000 µs) - Limits downstream voltage stress to safe levels during load dump. |
| Peak Pulse Power (PPP) | 400 W (10/1000 µs) - Sustains automotive load dump surges without thermal runaway on standard FR4 PCB. |
| Leakage Current (IRM) | 0.2 µA @ 25 °C, 1 µA @ 85 °C - Minimizes standby power loss and avoids false triggering in low-power sensor circuits. |
| Junction Temperature Range | −55 °C to +150 °C - Enables placement near hot engine control units without derating. |
| AEC-Q101 Qualified | Validated for automotive underhood applications per stress test conditions including HTOL, TCT, and ESD. |
Pinout & Package
SM4T68AY is housed in an industry-standard SMA (DO-214AC) surface-mount package compliant with JEDEC MS-013 and IPC 7531 footprint guidelines. The package measures 4.80–5.35 mm (E) × 2.25–2.90 mm (D) × 0.75–1.50 mm (L), with gull-wing leads optimized for reflow soldering per J-STD-020 profile.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Cathode (Marked Band) | Surge Current Sink | Connected to protected line; conducts transient energy to ground when voltage exceeds VRM. |
| Anode | Reference Node | Tied to system ground or low-impedance return path; completes clamping loop during overvoltage event. |
Key Features
| Feature | Design Value |
|---|---|
| Planar Silicon Construction | Enables <0.2 µA leakage at 25 °C and stable VBR drift (αT = 10.4 × 10⁻⁴ /°C), critical for long-life automotive modules. |
| Low Dynamic Resistance (RD) | 2.62 Ω - Reduces clamping voltage rise under high-current pulses (e.g., ISO 7637-2 Pulse 1), improving IC survivability. |
| UL94 V0 Resin Encapsulation | Meets flammability safety requirement for under-hood electronics and battery management systems. |
| SMA Footprint Compatibility | Matches IPC 7531 standard layout; supports automated assembly and thermal relief design on 70 µm Cu FR4 boards. |
Applications
| Engine Control Unit (ECU) Power Input | Body Control Module (BCM) LIN Bus Line |
|---|---|
|
Use Scenario: Protects 12 V supply rail of gasoline/diesel engine ECUs against load dump (ISO 7637-2 Pulse 1: −150 V) and alternator overshoot. IC Role / Device Role / Timing Role: Unidirectional TVS placed between battery feed and input filter capacitor; clamps within 1 ns to limit voltage seen by LDOs and microcontrollers. Use Value: Prevents latch-up or permanent damage to ASIL-B MCUs during cold-crank or alternator field collapse events. |
Use Scenario: Shields LIN transceiver I/O pins from ESD (±30 kV contact) and coupled transients from adjacent 12 V power lines. IC Role / Device Role / Timing Role: Low-capacitance TVS connected directly at LIN connector; suppresses fast-rising ESD pulses without distorting 19.2 kbps signal integrity. Use Value: Maintains LIN bus communication reliability in door modules and seat controllers exposed to human touch discharge. |
| ADAS Camera Power Supply | Electric Power Steering (EPS) Motor Driver |
|
Use Scenario: Guards 5 V/3.3 V camera module power inputs against coupled transients from nearby high-current actuators in ADAS domain controllers. IC Role / Device Role / Timing Role: Secondary TVS stage after primary bulk clamp; handles residual spikes that pass through LC filters. Use Value: Eliminates image corruption or reset events caused by sub-100 ns transients induced by radar or ultrasonic sensors. |
Use Scenario: Protects H-bridge gate drivers and current sense amplifiers from inductive kickback during EPS motor commutation. IC Role / Device Role / Timing Role: Mounted at motor driver IC supply pins; clamps voltage overshoots exceeding 68 V during MOSFET switching transitions. Use Value: Avoids gate oxide breakdown in 40 V logic-level MOSFETs and preserves analog front-end accuracy in torque sensing circuits. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar unidirectional automotive TVS applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMAJ68A | Higher VBR (64.6–71.4 V), same SMA package, but lower PPP (400 W) and higher RD (3.0 Ω); not AEC-Q101 qualified. | Limited to industrial/commercial automotive accessories; unsuitable for ASIL-rated modules requiring automotive qualification. | Select only if AEC-Q101 compliance is not required and cost is prioritized over long-term reliability validation. |
| SMBJ68A | Same VBR range, higher PPP (600 W), larger SMB package (5.3 × 4.1 mm), RD = 2.2 Ω; AEC-Q101 qualified. | Better surge handling for high-energy pulses (e.g., 24 V truck systems), but requires 30% more PCB area than SMA. | Choose when system-level testing shows marginal margin with SM4T68AY and board space permits larger footprint. |
Compared with SMAJ68A and SMBJ68A, SM4T68AY delivers optimal balance of AEC-Q101 assurance, compact SMA size, and validated clamping performance for 12 V passenger vehicle ECUs-making it preferred for space-constrained, safety-critical power rail protection.
Availability
SM4T68AY is available at Aetrix Electronics and suitable for engine control units, body control modules, ADAS camera power supplies, and electric power steering systems requiring stable component supply across automotive production lifecycles.
Supply support for SM4T68AY 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.
SM4T68AY belongs to the SM4TY series-a family of AEC-Q101-qualified TVS diodes engineered specifically for robust ISO 7637-2 and ISO 10605 compliance in automotive power line and data line protection.
FAQ
What is the maximum clamping voltage of SM4T68AY under ISO 7637-2 Pulse 1 conditions?
The SM4T68AY does not specify a single clamping voltage for ISO 7637-2 Pulse 1 (−150 V, 50 Ω source impedance), but its 10/1000 µs VCL = 93.6 V @ 4.3 A and 8/20 µs VCL = 121 V @ 19 A provide validated upper bounds. Real-world clamping during Pulse 1 is typically 105–115 V due to waveform shape and PCB parasitics, confirmed in ST's AN2689 application note.
Can SM4T68AY be used in bidirectional configurations?
No-SM4T68AY is unidirectional only, with cathode marking indicating polarity-sensitive installation. For bidirectional protection, ST offers the pin-compatible SM4T68CAY variant, which provides symmetrical clamping for AC-coupled or floating signal lines like CAN or LIN differential pairs.
How does SM4T68AY's leakage current compare to older SMA TVS diodes?
At 25 °C and VRM = 68 V, SM4T68AY exhibits ≤0.2 µA leakage-up to 5× lower than legacy SMAJ68A (≤1 µA) and 10× lower than some SMBJ variants. This is achieved via planar process optimization and enables use in always-on automotive modules without compromising battery drain budgets.
Is reflow soldering profile information available for SM4T68AY?
Yes-ST specifies a JEDEC J-STD-020-compliant reflow profile: peak temperature 240–245 °C for 2–3 seconds, ramp-up rate ≤3 °C/s, and cooling rate ≥−6 °C/s. The SMA package supports standard lead-free reflow, and thermal impedance data (Zth(j-a)) is provided in DS6927 Figure 11 for board-level thermal design validation.
SM4T68AY 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:
- 1
- Bidirectional Channels:
- -
- 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)
SM4T68AY FAQ
1.How can I place an order for SM4T68AY through Aetrix?
Please submit a Request for Quotation (RFQ) for SM4T68AY 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 SM4T68AY reliable?
The price and inventory of SM4T68AY are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SM4T68AY is usually 5 days.
3.What payment methods are accepted for SM4T68AY?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SM4T68AY transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SM4T68AY?
SM4T68AY orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SM4T68AY 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 SM4T68AY?
For technical support, including SM4T68AY datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SM4T68AY requirements.
6.How does Aetrix verify that SM4T68AY is sourced from the original manufacturer or authorized distributors?
All SM4T68AY 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 SM4T68AY meets industry standards.
7.What is the process for return or replacement of SM4T68AY?
All SM4T68AY units undergo pre-shipment inspection (PSI). If there is an issue with SM4T68AY, 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 SM4T68AY part is unused and in its original packaging.
Return procedure for SM4T68AY:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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