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STMicroelectronics SM50T21AY
- Part No.:
- SM50T21AY
- Manufacturer:
- STMicroelectronics
- Category:
- TVS Diodes
- Package:
- DO-214AB, SMC
- Datasheet:
-
SM50T21AY.pdf
- Description:
- AUTOMOTIVE 5000 W, 18 V TVS IN S
- Quantity:
- Payment:
- Shipping:
Inventory:2,450
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Product details
Overview
SM50T21AY from STMicroelectronics is an AEC-Q101-qualified unidirectional automotive TVS diode in SMC package, designed to clamp transient surges up to 5000 W (10/1000 µs) and 48 kW (8/20 µs), with a standoff voltage of 21 V (VRWM = 21 V), clamping voltage of 29.2 V at 171 A, and leakage current ≤0.2 µA at 25 °C. It protects CAN, LIN, and power supply lines in engine control units and body electronics against ISO 7637-2 pulses and ISO 10605 ESD.
For engineers reviewing the SM50T21AY datasheet, SM50T21AY pinout, SM50T21AY application, or SM50T21AY equivalent, key selection criteria include clamping performance under 8/20 µs surge, junction temperature capability up to +175 °C, low dynamic resistance (18.0 mΩ), compliance with ISO 16750 load dump test B, and SMC package thermal robustness on FR4 PCBs.
Technical Context
This unidirectional TVS diode uses planar silicon technology to achieve stable breakdown behavior across -55 °C to +175 °C operating junction temperature, with temperature coefficient αT = 10 × 10−4/°C for both VBR and VCL. Its low leakage (<0.2 µA at 25 °C) and high surge immunity support long-term reliability in harsh automotive environments.
The device meets IEC 61000-4-2 level 4 (±30 kV contact/air), ISO 10605 (±30 kV), and ISO 7637-2 pulse 1 (−150 V), 2a (+112 V), 3a (−220 V), and 3b (+150 V), enabling direct placement on 12 V battery-fed circuits without additional filtering.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VRWM | 21 V - Maximum continuous reverse working voltage before conduction begins; sets minimum system operating margin. |
| VBR min / typ / max | 20 / 21.1 / 22.2 V at IR = 1 mA - Precise breakdown threshold ensures predictable clamping onset in 12 V automotive networks. |
| VCL @ 10/1000 µs | 29.2 V at IPP = 171 A - Clamping voltage limits downstream IC stress during slow transients like load dump. |
| VCL @ 8/20 µs | 40.9 V at IPP = 39.3 A - Higher clamping under fast surges reflects dynamic resistance (18.0 mΩ) limiting peak voltage overshoot. |
| IR max | 0.2 µA at VRWM = 21 V and Tj = 25 °C - Ultra-low leakage preserves signal integrity and reduces standby power loss in always-on modules. |
| PPP | 5000 W (10/1000 µs), up to 48 kW (8/20 µs) - Peak power rating defines maximum energy absorption capacity per transient event. |
| Tj max | +175 °C - Enables operation in under-hood ECUs where ambient temperatures exceed 125 °C and thermal derating is critical. |
Pinout & Package
SM50T21AY is housed in a JEDEC-registered SMC (DO-214AB) surface-mount package with matte tin-plated leads, compatible with standard reflow profiles (peak 240–245 °C). The package features two terminals: cathode (marked with bar) and anode.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Cathode (bar-marked) | Transient voltage reference node | Connected to protected line (e.g., CAN_H); conducts during positive transients to clamp voltage to VCL. |
| Anode | Return path to ground or lower-potential rail | Provides low-inductance discharge path; must be routed with minimal loop area to preserve clamping speed and effectiveness. |
Key Features
| Feature | Design Value |
|---|---|
| AEC-Q101 qualification | Validated for automotive-grade reliability including temperature cycling, humidity bias, and mechanical shock per AEC standard. |
| Low dynamic resistance | 18.0 mΩ - Minimizes VCL rise under high-current surges, improving protection margin for 5 V or 3.3 V downstream logic. |
| High junction temperature rating | +175 °C operating limit - Supports placement near heat sources (e.g., power MOSFETs) without derating or thermal shutdown. |
| ISO 7637-2 pulse compliance | Passes Pulse 1 (−150 V), Pulse 2a (+112 V), Pulse 3a (−220 V), Pulse 3b (+150 V) - Enables single-device protection for full vehicle-level EMC testing. |
| ESD robustness | ±30 kV contact/air per IEC 61000-4-2 and ISO 10605 - Eliminates need for secondary ESD suppressors on exposed connectors and sensors. |
Applications
| Engine Control Unit (ECU) | Body Control Module (BCM) |
|---|---|
|
Use Scenario: Protects 12 V power input and CAN bus lines from alternator load dump and ignition coil switching noise. IC Role / Device Role / Timing Role: Unidirectional TVS placed between battery rail and LDO input, clamping transients within 1 ns response time. Use Value: Prevents latch-up or permanent damage to microcontroller power domains during ISO 7637-2 Pulse 5b events (87 V, 150 ms). |
Use Scenario: Shields LIN bus transceivers and door module switches from ESD and battery reversal-induced surges. IC Role / Device Role / Timing Role: Standoff-rated TVS on LIN data line, absorbing ±30 kV contact discharge while maintaining <0.2 µA leakage at 12 V. Use Value: Ensures uninterrupted communication during factory handling and service operations without signal distortion or false wake-ups. |
| Advanced Driver Assistance Systems (ADAS) Camera Power Supply | Electric Power Steering (EPS) Motor Driver Interface |
|
Use Scenario: Guards 5 V camera sensor power rail against coupled transients from nearby DC-DC converters and motor drivers. IC Role / Device Role / Timing Role: Secondary TVS after primary filter, clamping residual spikes to ≤29.2 V to protect image sensor analog front-end. Use Value: Maintains clean power delivery under combined ISO 7637-2 Pulse 3a/b and ESD stress, preventing pixel corruption or frame dropouts. |
Use Scenario: Protects H-bridge gate driver inputs from inductive kickback when steering motor commutates. IC Role / Device Role / Timing Role: Fast-response TVS on logic-level enable lines, limiting voltage to 40.9 V during 8/20 µs motor-switching surges. Use Value: Avoids false triggering or destruction of isolated gate drivers, ensuring torque command fidelity and functional safety compliance. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient voltage suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMAJ22A | Lower peak power (400 W), higher VCL (35.5 V @ 10/1000 µs), non-AEC-Q101 rated | Limited to non-automotive industrial use; insufficient for ISO 7637-2 Pulse 1 or load dump | Select only for cost-sensitive consumer applications where AEC-Q101 and 5000 W surge rating are not required. |
| TPSMD22A | Same SMC package, AEC-Q101 qualified, but VRWM = 22 V, VCL = 32.4 V @ 155 A (10/1000 µs), lower PPP (4000 W) | Marginally lower clamping and power handling; may require derating in high-energy pulse environments | Acceptable for BCM or lighting modules with moderate surge exposure, but not recommended for engine bay ECUs. |
Compared with SMAJ22A and TPSMD22A, SM50T21AY delivers superior automotive-grade surge resilience-5000 W peak power, 29.2 V clamping at 171 A, and full ISO 7637-2 compliance-making it the only choice for mission-critical power and data line protection in under-hood and safety-critical systems.
Availability
SM50T21AY is available at Aetrix Electronics and suitable for engine control units, body control modules, ADAS camera power supplies, and electric power steering interfaces requiring stable component supply across automotive production lifecycles.
Supply support for SM50T21AY 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 intelligent power, sensing, and control solutions for automotive, industrial, and consumer markets.
The SM50TxxAY series belongs to ST's automotive-grade transient voltage suppression portfolio, engineered specifically for robust, high-temperature, high-energy surge protection in 12 V and 24 V vehicle electrical architectures.
FAQ
What is the maximum clamping voltage of SM50T21AY under a 10/1000 µs surge?
The maximum clamping voltage is 29.2 V at 171 A for a 10/1000 µs waveform, measured at Tj = 25 °C. This value increases with junction temperature at a rate defined by αT = 10 × 10−4/°C, reaching approximately 31.5 V at Tj = 125 °C per the VCL vs. Tj formula in DS13895.
Is SM50T21AY suitable for bidirectional signal lines like CAN or LIN?
No-SM50T21AY is unidirectional and intended for DC power rails or single-ended signal lines referenced to ground. For bidirectional data buses such as CAN, the SM50T21CAY variant (with "C" suffix) must be used, as it provides symmetrical clamping for both polarities without polarity-dependent conduction.
How does the SMC package affect thermal performance in high-power surge events?
The SMC package enables effective heat dissipation via copper pour under both leads: Rth(j-a) drops from ~120 °C/W (no copper) to ~40 °C/W with 3 cm² copper area per lead. This allows sustained operation at +175 °C junction temperature during repetitive surges, provided PCB layout follows ST's footprint recommendation (5.11 mm × 8.19 mm pad size).
Does SM50T21AY meet ISO 16750-2 test requirements?
Yes-SM50T21AY is explicitly validated for ISO 16750-2 Test B (load dump), supporting Us = 87 V with pulse durations of 150 ms and 400 ms. Its 5000 W peak power rating and low dynamic resistance ensure reliable clamping without thermal runaway during extended overvoltage conditions typical in modern vehicle electrical systems.
SM50T21AY 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):
- 18V (Max)
- Voltage - Breakdown (Min):
- 20V
- Voltage - Clamping (Max) @ Ipp:
- 29.2V
- Current - Peak Pulse (10/1000µs):
- 171A
- 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
SM50T21AY FAQ
1.How can I place an order for SM50T21AY through Aetrix?
Please submit a Request for Quotation (RFQ) for SM50T21AY 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 SM50T21AY reliable?
The price and inventory of SM50T21AY are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SM50T21AY is usually 5 days.
3.What payment methods are accepted for SM50T21AY?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SM50T21AY transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SM50T21AY?
SM50T21AY orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SM50T21AY 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 SM50T21AY?
For technical support, including SM50T21AY datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SM50T21AY requirements.
6.How does Aetrix verify that SM50T21AY is sourced from the original manufacturer or authorized distributors?
All SM50T21AY 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 SM50T21AY meets industry standards.
7.What is the process for return or replacement of SM50T21AY?
All SM50T21AY units undergo pre-shipment inspection (PSI). If there is an issue with SM50T21AY, 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 SM50T21AY part is unused and in its original packaging.
Return procedure for SM50T21AY:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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