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STMicroelectronics SMA4F12A
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- Part No.:
- SMA4F12A
- Manufacturer:
- STMicroelectronics
- Category:
- TVS Diodes
- Package:
- DO-221AC, SMA Flat Leads
- Datasheet:
-
SMA4F12A.pdf
- Description:
- TVS DIODE 12VWM 25.3VC SMAFLAT
- Quantity:
- Payment:
- Shipping:
Inventory:2,602
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Product details
Overview
SMA4F12A from STMicroelectronics is a unidirectional 400 W transient voltage suppression (TVS) diode designed for primary-level surge protection in DC power rails and signal lines. It features a 12 V stand-off voltage (VRM), 13.3–14.7 V breakdown voltage (VBR) at 1 mA, clamps to ≤19.9 V at 20.1 A (10/1000 µs), and operates up to 175 °C junction temperature - enabling robust protection in automotive body electronics and industrial power supplies.
For engineers reviewing the SMA4F12A datasheet, SMA4F12A pinout, SMA4F12A application, or SMA4F12A equivalent, key selection criteria include clamping voltage under 20 A surge, low leakage (<1 µA at 85 °C), high-temperature reliability, and compatibility with standard SMA flat package PCB footprints per IPC7531.
Technical Context
The SMA4F12A employs planar silicon avalanche technology to deliver precise, repeatable clamping behavior during fast transients. Its unidirectional configuration supports DC-biased lines where reverse polarity is not expected, and its low dynamic resistance (0.259 Ω) ensures minimal voltage overshoot during 10/1000 µs surges.
Thermal performance is validated across -55 °C to +175 °C operating range, with peak pulse power derating to 200 W at Tj = 175 °C. The device meets IEC 61000-4-2 Level 4 ESD immunity (±25 kV contact / ±30 kV air) and complies with J-STD-020 MSL Level 1, supporting lead-free reflow without preconditioning.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Stand-off Voltage (VRM) | 12 V - maximum continuous reverse working voltage before leakage exceeds 0.2 µA at 25 °C |
| Breakdown Voltage (VBR) | 13.3–14.7 V at 1 mA - defines onset of avalanche conduction; tight tolerance enables predictable trigger point |
| Clamping Voltage (VCL) | ≤19.9 V at 20.1 A (10/1000 µs) - limits downstream voltage stress during surge events |
| Peak Pulse Power (PPP) | 400 W (10/1000 µs), 2.5 kW (8/20 µs) - sustains high-energy transients without failure |
| Leakage Current (IRM) | 0.2 µA max at VRM and 25 °C; 1 µA max at 85 °C - ensures minimal standby power loss in battery-critical systems |
| Junction Temperature Range | -55 °C to +175 °C - supports under-hood automotive and industrial environments without derating |
| Dynamic Resistance (RD) | 0.259 Ω - determines VCL rise slope (ΔV = RD × IPP); critical for low-voltage rail protection |
Pinout & Package
The SMA4F12A uses the industry-standard SMA Flat (DO-214AC) surface-mount package: 2.25–2.90 mm length, 5.00–5.35 mm width, 0.90–1.10 mm height, matte tin-plated leads, and IPC7531-compliant footprint.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Cathode (Marked Band) | Surge current sink terminal | Connected to protected line; conducts avalanche current to ground during overvoltage |
| Anode | Reference/return path | Typically tied to system ground or low-impedance return plane; completes transient current loop |
Key Features
| Feature | Design Value |
|---|---|
| High-temperature operation | Rated for continuous use up to 175 °C junction temperature - eliminates thermal derating in compact enclosures |
| Low-leakage planar junction | 0.2 µA IRM at 25 °C enables use in always-on sensor nodes and low-power IoT endpoints |
| IEC 61000-4-2 Level 4 compliance | Withstands ±25 kV contact and ±30 kV air discharge - exceeds automotive EMC requirements (ISO 10605) |
| MSL Level 1 moisture sensitivity | Zero floor life limitation - can be mounted directly from reel without baking or dry pack handling |
| JEDEC-registered SMA outline | Guarantees mechanical compatibility with automated placement equipment and standard reflow profiles |
Applications
| Automotive Body Control Module (BCM) | Industrial PLC Digital Input |
|---|---|
Use Scenario: Protecting 12 V supply inputs against load dump and ISO 7637-2 pulses in door module ECUs. IC Role / Device Role / Timing Role: Primary TVS clamp on main power rail, placed upstream of LDOs and microcontrollers. Use Value: Clamps to ≤19.9 V within nanoseconds, preventing latch-up or damage to 24 V-tolerant interface ICs. |
Use Scenario: Safeguarding 24 V digital input channels from field-wiring induced surges in factory automation cabinets. IC Role / Device Role / Timing Role: Front-end transient suppressor before optocoupler or Schmitt-trigger input stage. Use Value: Low dynamic resistance ensures fast response and minimal voltage overshoot during 1 kV/µs transients. |
| Telecom Power Supply OVP | Smart Meter AC/DC Auxiliary Rail |
Use Scenario: Overvoltage protection on +48 V telecom rectifier outputs exposed to lightning-induced surges. IC Role / Device Role / Timing Role: Secondary surge clamp after MOV-based primary protection, absorbing residual energy. Use Value: 400 W peak power rating handles residual 10/1000 µs tail energy that bypasses upstream protection. |
Use Scenario: Protecting isolated 5 V auxiliary supply derived from mains in revenue-grade electricity meters. IC Role / Device Role / Timing Role: Standoff-rated TVS on secondary-side DC output, guarding metering SoC and RTC circuitry. Use Value: 12 V VRM matches typical LDO dropout margin; 0.2 µA leakage preserves battery backup runtime. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar unidirectional TVS diode applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMAJ12A (Bourns) | Same SMA package, 400 W rating, but higher VBR (13.3–14.7 V → 13.3–15.8 V) and higher VCL (20.1 V → 21.2 V at 20.1 A) | Marginally higher clamping may risk overstress on 16 V-tolerant ICs; suitable where layout allows tighter layout control | Select when sourcing diversification is required and 1.1 V higher clamping is acceptable in system margin analysis |
| SMBJ12A (Littelfuse) | SMB package (larger footprint), same 12 V VRM, but lower PPP (600 W vs 400 W) and higher RD (0.35 Ω vs 0.259 Ω) | Requires more PCB area; higher dynamic resistance yields ~1.5 V higher clamping at same IPP | Choose only if SMB footprint is already standardized in design and thermal mass requirements exceed SMA capability |
Compared with SMAJ12A and SMBJ12A, the SMA4F12A offers the lowest clamping voltage (19.9 V) and dynamic resistance (0.259 Ω) in SMA form factor, making it optimal for space-constrained, low-voltage-rail protection where precise voltage limiting is critical.
Availability
SMA4F12A is available at Aetrix Electronics and suitable for automotive body electronics, industrial PLC input protection, telecom power supply OVP, and smart meter auxiliary rail designs requiring stable component supply and long-term lifecycle support.
Supply support for SMA4F12A 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 discrete technologies with vertical manufacturing capabilities.
The SMA4F series belongs to ST's Transil™ TVS portfolio, engineered specifically for high-reliability transient suppression in harsh-environment applications demanding extended temperature operation and low leakage.
FAQ
What is the maximum clamping voltage of SMA4F12A under a 10/1000 µs surge?
The SMA4F12A clamps to a maximum of 19.9 V when subjected to a 20.1 A peak pulse with 10/1000 µs waveform, as specified in Table 2 of DS12542 Rev 1. This value is measured at Tamb = 25 °C and represents the upper limit of voltage seen by downstream circuitry during such an event.
Does SMA4F12A require moisture sensitivity level (MSL) baking before reflow?
No - SMA4F12A is rated MSL Level 1 per J-STD-020, meaning it has unlimited floor life and may be placed directly from tape-and-reel without dry-pack storage or pre-reflow baking, simplifying SMT assembly logistics.
Can SMA4F12A be used in bidirectional signal line protection?
No - SMA4F12A is unidirectional (Type A), intended for DC-biased lines like power rails. For bidirectional signal lines (e.g., RS-485, USB), ST recommends the SMA4F12CA variant or other symmetric TVS devices with equal positive/negative clamping.
How does junction temperature affect the clamping voltage of SMA4F12A?
VCL increases with junction temperature at a rate defined by αT = 8.3 × 10−4/°C. At 175 °C, VCL rises approximately 12.5% above its 25 °C value - e.g., 19.9 V becomes ~22.4 V at full-rated temperature, which must be accounted for in worst-case margin analysis.
SMA4F12A 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):
- 12V
- Voltage - Breakdown (Min):
- 13.3V
- Voltage - Clamping (Max) @ Ipp:
- 25.3V
- Current - Peak Pulse (10/1000µs):
- 20.1A
- 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
SMA4F12A FAQ
1.How can I place an order for SMA4F12A through Aetrix?
Please submit a Request for Quotation (RFQ) for SMA4F12A 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 SMA4F12A reliable?
The price and inventory of SMA4F12A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMA4F12A is usually 5 days.
3.What payment methods are accepted for SMA4F12A?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMA4F12A transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMA4F12A?
SMA4F12A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMA4F12A 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 SMA4F12A?
For technical support, including SMA4F12A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMA4F12A requirements.
6.How does Aetrix verify that SMA4F12A is sourced from the original manufacturer or authorized distributors?
All SMA4F12A 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 SMA4F12A meets industry standards.
7.What is the process for return or replacement of SMA4F12A?
All SMA4F12A units undergo pre-shipment inspection (PSI). If there is an issue with SMA4F12A, 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 SMA4F12A part is unused and in its original packaging.
Return procedure for SMA4F12A:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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