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STMicroelectronics SM4T28CAY
- Part No.:
- SM4T28CAY
- Manufacturer:
- STMicroelectronics
- Category:
- TVS Diodes
- Package:
- DO-214AC, SMA
- Datasheet:
-
SM4T28CAY.pdf
- Description:
- TVS DIODE 24VWM 50VC SMA
- Quantity:
- Payment:
- Shipping:
Inventory:21,675
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Product details
Overview
SM4T28CAY from STMicroelectronics is a bidirectional 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 28 V stand-off voltage (VRM), 38.9 V clamping voltage at 10.3 A (10/1000 µs), and 400 W peak pulse power rating at 25 °C.
For engineers reviewing the SM4T28CAY datasheet, SM4T28CAY pinout, SM4T28CAY application, or SM4T28CAY equivalent, this device is selected for high-reliability 12 V automotive power line protection where low leakage (0.2 µA @ 25 °C), AEC-Q101 qualification, and junction temperature operation up to 150 °C are mandatory.
Technical Context
The SM4T28CAY employs planar silicon technology to achieve stable breakdown behavior across temperature and low dynamic resistance (0.446 Ω) under 8/20 µs surges. Its bidirectional configuration enables symmetrical clamping on both polarities without external polarity management.
It meets stringent automotive surge standards including ISO 7637-2 Pulse 1 (inductive load dump reversal), Pulse 2a (battery feed interruption), and Pulse 3a/3b (capacitive coupling transients), with validated clamping performance up to 50 A (8/20 µs) and 10.3 A (10/1000 µs).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Stand-off Voltage (VRM) | 28 V - Maximum continuous reverse operating voltage before conduction begins; matches 12 V automotive battery systems with margin against ripple and transients. |
| Breakdown Voltage (VBR) | 26.7–29.5 V @ 1 mA - Confirmed min/typ/max range ensures reliable triggering across production lot and temperature (−55 to +150 °C). |
| Clamping Voltage (VCL) | 38.9 V @ 10.3 A (10/1000 µs) - Limits downstream circuit voltage during surge; enables robust protection of 40 V-rated CAN/LIN transceivers and microcontrollers. |
| Peak Pulse Power (PPP) | 400 W @ 10/1000 µs - Sustains standardized long-duration load dump energy without thermal runaway; derates to 200 W at Tj = 125 °C per curve Fig.3. |
| Leakage Current (IRM) | 0.2 µA @ 25 °C, 1 µA @ 85 °C - Minimizes standby power loss and avoids false triggering in always-on vehicle modules (e.g., body control units). |
| ESD Withstand | ±30 kV (IEC 61000-4-2, 150 pF/330 Ω & 330 pF/330 Ω) - Fully qualifies for touch-sensitive infotainment and ADAS sensor interfaces without external ESD staging. |
| Junction Temp Range | −55 to +150 °C - Supports under-hood placement (e.g., engine control modules) with no derating required up to max rated ambient. |
Pinout & Package
SM4T28CAY is housed in an industry-standard SMA (DO-214AC) surface-mount package per JEDEC MS-013AA, with cathode band marking and UL94 V0-compliant resin. The two-terminal device has no polarity-specific pin numbering; terminals are symmetrically designated Anode and Cathode for bidirectional operation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Surge current entry (negative polarity) | Accepts reverse-polarity transients (e.g., ISO 7637-2 Pulse 1: −150 V); forms low-impedance path to ground when voltage exceeds VRM. |
| Cathode | Surge current entry (positive polarity) | Accepts positive transients (e.g., Pulse 2a: +112 V); clamps voltage to ≤38.9 V during 10.3 A surge, protecting downstream ICs. |
Key Features
| Feature | Design Value |
|---|---|
| AEC-Q101 qualified | Validated for automotive use per stress test requirements (HTOL, TC, HTRB, UHAST), enabling deployment in safety-critical ECUs without additional qualification. |
| Bidirectional clamping | Single-device protection against both positive and negative transients-eliminates need for dual-diode configurations or polarity-aware layout. |
| Low dynamic resistance (RD) | 0.446 Ω @ 8/20 µs - Reduces clamping voltage overshoot during fast-rising surges (e.g., ESD), improving margin for 3.3 V/5 V logic rails. |
| High junction temperature rating | 150 °C max operating Tj - Enables direct placement near heat sources (e.g., power MOSFETs in motor drivers) without thermal derating penalties. |
| UL94 V0 resin package | Flame-retardant encapsulation compliant with automotive cabin safety standards-required for interior and dashboard-mounted electronics. |
Applications
| Engine Control Unit (ECU) | Body Control Module (BCM) |
|---|---|
|
Use Scenario: Protects LIN bus interface and 5 V regulator input from load dump and alternator ripple in gasoline/diesel engine compartments. IC Role / Device Role / Timing Role: Bidirectional TVS placed directly at connector entry point to clamp transients before they reach MCU I/O and LDOs. Use Value: Maintains system uptime during repeated −150 V Pulse 1 events; eliminates need for redundant protection stages due to 400 W rating and 150 °C Tj capability. |
Use Scenario: Shields door module microcontrollers and window motor drivers from ESD and capacitive coupling noise in passenger cabin wiring harnesses. IC Role / Device Role / Timing Role: Standoff-clamp TVS on 12 V supply rail and LIN signal lines, leveraging ±30 kV ESD rating and low 0.2 µA leakage. Use Value: Prevents firmware lockup and reset faults caused by contact discharge near switches; supports always-on functionality with negligible quiescent current impact. |
| Advanced Driver Assistance Systems (ADAS) | Infotainment Head Unit |
|
Use Scenario: Safeguards camera power inputs and CAN FD communication lines against battery disconnection spikes and electromagnetic coupling in front-end radar/camera modules. IC Role / Device Role / Timing Role: Primary surge suppressor on 12 V input and CAN_H/CAN_L differential pairs, operating within −40 to +105 °C ambient range. Use Value: Ensures uninterrupted video streaming and sensor fusion during ISO 7637-2 Pulse 3a/3b events (−200 V/+150 V), preserving functional safety integrity. |
Use Scenario: Guards USB-C power delivery and HDMI signal lines from user-handling ESD and hot-plug transients in center console displays. IC Role / Device Role / Timing Role: Secondary-level TVS on auxiliary power rails and high-speed data lines, complementing internal SoC ESD structures. Use Value: Achieves full IEC 61000-4-2 compliance without board space penalty-SMA footprint fits tight routing constraints near connectors. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bidirectional TVS diode applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMBJ28CA | Same VRM (28 V) and bidirectional configuration, but SMB package (larger footprint, higher thermal mass); 600 W PPP (10/1000 µs) vs. 400 W. | Preferred where PCB space allows larger package and higher surge margin is needed (e.g., commercial truck 24 V systems). | Select SMBJ28CA only if layout permits SMB footprint and system requires >400 W surge handling-SM4T28CAY offers superior density and AEC-Q101 traceability. |
| 1.5KE27CA | Through-hole DO-201 package; 27 V VRM (slightly lower), 400 W rating, but not AEC-Q101 qualified and lacks ISO 7637-2 validation. | Limited to non-automotive industrial controls; unsuitable for automotive production due to missing qualification and standard compliance. | Reject for automotive use-lacks AEC-Q101, ISO 7637-2 pulse validation, and surface-mount compatibility required for modern ECU assembly. |
Compared with SMBJ28CA and 1.5KE27CA, SM4T28CAY delivers optimal balance of automotive qualification, SMA footprint density, and verified ISO 7637-2/Pulse 3b performance-making it the default choice for space-constrained, safety-certified 12 V vehicle networks.
Availability
SM4T28CAY is available at Aetrix Electronics and suitable for engine control units, body control modules, ADAS camera power supplies, and infotainment head unit interfaces requiring stable component supply across automotive production lifecycles.
Supply support for SM4T28CAY 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 over 40 years of analog protection IP development.
The SM4Txx series belongs to ST's automotive-grade TVS portfolio, engineered specifically for robustness against load dump, ESD, and coupled transients in 12 V vehicle electrical architectures-prioritizing AEC-Q101 reliability and ISO standard compliance.
FAQ
Is SM4T28CAY unidirectional or bidirectional?
SM4T28CAY is a bidirectional TVS diode, indicated by the "CAY" suffix per ST's ordering nomenclature. It provides symmetrical clamping for both positive and negative transients, eliminating the need for polarity-aware placement or dual-diode arrangements in 12 V automotive power rails.
What is the maximum clamping voltage under 8/20 µs surge conditions?
Under 8/20 µs surge conditions, SM4T28CAY clamps to 50 V at 46 A (per Table 2, row SM4T28AY/CAY). This value is derived from VCL = VBR(max) + RD × IPP = 29.5 V + 0.446 Ω × 46 A ≈ 50 V, ensuring safe operation for 40 V-rated downstream components.
Does SM4T28CAY meet ISO 7637-2 Pulse 1 requirements?
Yes-SM4T28CAY is explicitly validated for ISO 7637-2 Pulse 1 (VS = −150 V, 12 V battery reference) per the datasheet's Characteristics section and Figure 13. Its 38.9 V clamping at 10.3 A (10/1000 µs) and 50 V at 46 A (8/20 µs) ensure compliance with the −150 V test waveform's energy profile.
Can SM4T28CAY replace SM4T28AY in a design?
No-SM4T28AY is unidirectional (anode-cathode asymmetry), while SM4T28CAY is bidirectional. Substituting them requires verifying circuit polarity: SM4T28AY must be oriented with cathode toward protected line, whereas SM4T28CAY has no orientation constraint but provides symmetrical protection on both polarities.
SM4T28CAY 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):
- 24V
- Voltage - Breakdown (Min):
- 26.7V
- Voltage - Clamping (Max) @ Ipp:
- 50V
- Current - Peak Pulse (10/1000µs):
- 46A (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)
SM4T28CAY FAQ
1.How can I place an order for SM4T28CAY through Aetrix?
Please submit a Request for Quotation (RFQ) for SM4T28CAY 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 SM4T28CAY reliable?
The price and inventory of SM4T28CAY are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SM4T28CAY is usually 5 days.
3.What payment methods are accepted for SM4T28CAY?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SM4T28CAY transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SM4T28CAY?
SM4T28CAY orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SM4T28CAY 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 SM4T28CAY?
For technical support, including SM4T28CAY datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SM4T28CAY requirements.
6.How does Aetrix verify that SM4T28CAY is sourced from the original manufacturer or authorized distributors?
All SM4T28CAY 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 SM4T28CAY meets industry standards.
7.What is the process for return or replacement of SM4T28CAY?
All SM4T28CAY units undergo pre-shipment inspection (PSI). If there is an issue with SM4T28CAY, 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 SM4T28CAY part is unused and in its original packaging.
Return procedure for SM4T28CAY:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SM4T28CAY Tags
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