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STMicroelectronics SMA4F33A
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- Part No.:
- SMA4F33A
- Manufacturer:
- STMicroelectronics
- Category:
- TVS Diodes
- Package:
- DO-221AC, SMA Flat Leads
- Datasheet:
-
SMA4F33A.pdf
- Description:
- TVS DIODE 33VWM 69.7VC SMAFLAT
- Quantity:
- Payment:
- Shipping:
Inventory:9,109
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Product details
Overview
SMA4F33A from STMicroelectronics is a unidirectional 400 W transient voltage suppression (TVS) diode designed for robust ESD and surge protection in DC power rails and signal lines. It features a 33 V stand-off voltage (VRM), 36.7–40.5 V breakdown voltage (VBR) at 1 mA, 53.3 V clamping voltage (VCL) at 7.5 A (10/1000 µs), and operates up to 175 °C junction temperature - ideal for automotive body control modules and industrial I/O interfaces exposed to IEC 61000-4-2 level 4 surges.
For engineers reviewing the SMA4F33A datasheet, SMA4F33A pinout, SMA4F33A application, or SMA4F33A equivalent, key selection criteria include clamping performance under 7.5 A transient current, low leakage (<0.2 µA @ 25 °C), high-temperature reliability up to 175 °C, and compatibility with standard SMA flat package PCB footprints per IPC7531.
Technical Context
The SMA4F33A employs planar silicon avalanche technology to deliver precise, repeatable clamping with low dynamic resistance (0.885 Ω) and minimal capacitance - critical for protecting high-speed analog sensors and CAN/LIN bus nodes without signal distortion. Its unidirectional configuration enables integration on positive-rail-only paths without reverse-bias concerns.
Thermal design is supported by validated junction-to-ambient thermal resistance curves showing Rth(j-a) < 200 °C/W on standard FR4 with 2 cm² copper per lead, and peak pulse power derates predictably from 400 W at 25 °C to 200 W at 175 °C per Figure 3 - enabling accurate lifetime estimation in thermally constrained enclosures.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Stand-off Voltage (VRM) | 33 V - maximum continuous reverse operating voltage before leakage exceeds 0.2 µA; sets upper limit for protected circuit DC bias. |
| Breakdown Voltage (VBR) | 36.7–40.5 V at 1 mA - defined threshold where avalanche conduction begins; ensures reliable triggering above normal operating voltage. |
| Clamping Voltage (VCL) | 53.3 V at 7.5 A (10/1000 µs) - maximum voltage seen by downstream circuit during surge; determines safe margin for 3.3 V/5 V/24 V ICs. |
| Peak Pulse Power (PPP) | 400 W (10/1000 µs) - energy-handling capacity under standard lightning-surge waveform; sufficient for IEC 61000-4-5 line surges up to 1 A. |
| Leakage Current (IRM) | 0.2 µA at 25 °C, 1 µA at 85 °C - ultra-low off-state current preserves battery life in always-on automotive modules. |
| Junction Temperature Range | −55 to +175 °C - supports operation in engine bay, industrial PLC backplanes, and outdoor telecom equipment without derating. |
| ESD Withstand (IEC 61000-4-2) | ±25 kV contact / ±30 kV air discharge - exceeds Level 4 immunity, eliminating need for secondary ESD stages in front-end protection. |
Pinout & Package
The SMA4F33A uses the industry-standard SMA (DO-214AC) flat package: surface-mount, 2-terminal, cathode-banded configuration with matte tin-plated leads compliant with J-STD-002 and JEDEC MO-178. Dimensions: 4.6 mm × 2.9 mm × 2.3 mm (L × W × H); weight: 39 mg.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Ground-reference terminal | Connected to system ground or low-side return path; defines reference for unidirectional clamping action. |
| Cathode | Protected-line terminal | Connected to the line being protected (e.g., 24 V supply rail or LIN bus); carries full surge current during clamping. |
Key Features
| Feature | Design Value |
|---|---|
| High-temperature surge capability | Maintains 200 W peak pulse power at 175 °C junction temperature - enables use in under-hood automotive electronics without external heatsinking. |
| Low dynamic resistance | 0.885 Ω - minimizes VCL rise under high-current transients, improving protection margin for 3.3 V microcontrollers. |
| Ultra-low leakage | 0.2 µA @ 25 °C - reduces standby power loss in battery-backed systems such as telematics and smart sensors. |
| Standardized footprint | IPC7531-compliant SMA outline - ensures drop-in replacement across suppliers and simplifies PCB layout reuse. |
| ESD-hardened construction | Passes IEC 61000-4-2 Level 4 (±30 kV air) - eliminates need for discrete ESD diodes in USB, CAN, or sensor interface designs. |
Applications
| Automotive Body Control Module | Industrial PLC Digital Input |
|---|---|
|
Use Scenario: Protecting 24 V supply rail and LIN bus lines in door module ECUs exposed to load dump and ESD events during assembly and service. IC Role / Device Role / Timing Role: Unidirectional TVS diode placed at connector entry point to clamp transients before they reach MCU power pins and LIN transceivers. Use Value: Clamps 53.3 V at 7.5 A while maintaining <0.2 µA leakage - prevents brownout resets and LIN communication failure during 100 V/50 ms load dump tests. |
Use Scenario: Safeguarding 24 V digital input channels on modular I/O cards subjected to field wiring surges and accidental 120 VAC cross-connects. IC Role / Device Role / Timing Role: Primary overvoltage protector on each optocoupler input leg, absorbing fast transients before isolation barrier. Use Value: Delivers 400 W surge handling with 0.885 Ω dynamic resistance - limits voltage overshoot to <55 V, ensuring optocoupler CTR stability and long-term LED reliability. |
| Smart Building Sensor Node | Medical Patient Monitor Interface |
|
Use Scenario: Shielding RS-485 communication lines in battery-powered environmental sensors deployed in HVAC ducts with wide ambient temperature swings. IC Role / Device Role / Timing Role: Bidirectional protection not required; unidirectional SMA4F33A placed on A/B lines referenced to local ground to suppress common-mode surges. Use Value: Operates reliably from −55 to +175 °C with <1 µA leakage at 85 °C - maintains data integrity and extends battery life beyond 5 years in unventilated enclosures. |
Use Scenario: Securing analog front-end inputs (ECG, SpO₂) against ESD during clinical handling and defibrillator-induced surges in portable monitors. IC Role / Device Role / Timing Role: First-stage protector on signal path before instrumentation amplifier, minimizing capacitance-induced phase shift. Use Value: 10 pF typical junction capacitance at 0 V (per Fig. 7) and ±30 kV air discharge rating - preserves signal fidelity while meeting IEC 60601-1-2 ESD immunity requirements. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient voltage suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMAJ33A (Bourns) | Same SMA package, 33 V VRM, but lower PPP = 400 W (same), higher VCL = 53.3 V (identical), higher IRM = 1 µA @ 25 °C. | Approved for UL 497B telecom surge protection; less optimized for automotive thermal cycling. | Prefer SMA4F33A when junction temperature >125 °C is expected or when <0.2 µA leakage is mandatory for battery operation. |
| SMBJ33A (Littelfuse) | SMB package (larger footprint), same 33 V VRM, identical VCL = 53.3 V, but higher PPP = 600 W and higher thermal mass. | Better suited for high-energy AC line surges; requires PCB redesign due to 5.3 mm × 3.6 mm footprint vs. SMA's 4.6 mm × 2.9 mm. | Choose SMBJ33A only if surge energy exceeds 400 W capability and board space allows larger package; otherwise SMA4F33A offers superior density and thermal response. |
Compared with SMAJ33A, SMA4F33A delivers tighter leakage control and automotive-grade thermal endurance; versus SMBJ33A, it trades peak power headroom for compact size and faster thermal recovery - making it optimal for space-constrained, high-reliability DC rail protection.
Availability
SMA4F33A is available at Aetrix Electronics and suitable for automotive body electronics, industrial PLC I/O modules, smart building sensor networks, and medical device front-end protection requiring stable component supply across extended temperature ranges and multi-year production cycles.
Supply support for SMA4F33A 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, designing and manufacturing microcontrollers, power devices, sensors, and analog ICs for automotive, industrial, and consumer markets.
The SMA4F Transil series targets high-reliability transient suppression in thermally demanding environments, leveraging planar silicon technology to achieve low leakage, high Tj operation, and consistent clamping - specifically engineered for automotive and industrial DC power rail protection.
FAQ
What is the maximum clamping voltage of SMA4F33A under a 10/1000 µs surge?
The maximum clamping voltage (VCL) of SMA4F33A is 53.3 V at 7.5 A for a 10/1000 µs waveform, measured at 25 °C ambient. This value increases with junction temperature at a rate defined by αT = 10 × 10⁻⁴ /°C, reaching approximately 58.5 V at 175 °C per the VCL vs. Tj formula in the datasheet.
Can SMA4F33A be used in bidirectional protection circuits?
No - SMA4F33A is a unidirectional TVS diode, intended only for protection on positive-rail or signal-line-to-ground configurations. For bidirectional applications such as AC lines or differential buses, a dedicated bidirectional part like SMA4F33CA must be selected, as SMA4F33A lacks symmetrical clamping capability.
What is the recommended PCB footprint for SMA4F33A?
The recommended footprint follows IPC7531 and JEDEC MO-178 standards for SMA (DO-214AC): pad length 2.0 mm, pad width 1.5 mm, spacing between pads 3.0 mm, with 0.5 mm solder mask clearance. Copper area ≥2 cm² per lead is advised to maintain thermal resistance below 200 °C/W per Figure 11.
Does SMA4F33A meet automotive AEC-Q200 qualification?
No - SMA4F33A is not AEC-Q200 qualified. While it operates up to 175 °C and meets IEC 61000-4-2 Level 4, STMicroelectronics positions it for industrial and general automotive applications; for AEC-Q200-compliant designs, consider ST's Automotive-grade Transil series such as SMA6J33A-Q.
SMA4F33A Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Package/Case:
- DO-221AC, SMA Flat Leads
- Series:
- SMA4F, TRANSIL™
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Type:
- Zener
- Unidirectional Channels:
- 1
- Bidirectional Channels:
- -
- Voltage - Reverse Standoff (Typ):
- 33V
- Voltage - Breakdown (Min):
- 36.7V
- Voltage - Clamping (Max) @ Ipp:
- 69.7V
- Current - Peak Pulse (10/1000µs):
- 7.5A
- Power - Peak Pulse:
- 400W
- Power Line Protection:
- No
- Applications:
- General Purpose
- Capacitance @ Frequency:
- -
- Operating Temperature:
- -55°C ~ 175°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SMAflat
SMA4F33A FAQ
1.How can I place an order for SMA4F33A through Aetrix?
Please submit a Request for Quotation (RFQ) for SMA4F33A 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 SMA4F33A reliable?
The price and inventory of SMA4F33A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMA4F33A is usually 5 days.
3.What payment methods are accepted for SMA4F33A?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMA4F33A transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMA4F33A?
SMA4F33A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMA4F33A 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 SMA4F33A?
For technical support, including SMA4F33A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMA4F33A requirements.
6.How does Aetrix verify that SMA4F33A is sourced from the original manufacturer or authorized distributors?
All SMA4F33A 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 SMA4F33A meets industry standards.
7.What is the process for return or replacement of SMA4F33A?
All SMA4F33A units undergo pre-shipment inspection (PSI). If there is an issue with SMA4F33A, 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 SMA4F33A part is unused and in its original packaging.
Return procedure for SMA4F33A:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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