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STMicroelectronics SMA4F85A
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- Part No.:
- SMA4F85A
- Manufacturer:
- STMicroelectronics
- Category:
- TVS Diodes
- Package:
- DO-221AC, SMA Flat Leads
- Datasheet:
-
SMA4F85A.pdf
- Description:
- TVS DIODE 85VWM 137VC SMAFLAT
- Quantity:
- Payment:
- Shipping:
Inventory:9,798
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Product details
Overview
SMA4F85A 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 85 V stand-off voltage (VRM), 100 V typical breakdown voltage (VBR) at 1 mA, clamps to ≤137 V at 2.9 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 SMA4F85A datasheet, SMA4F85A pinout, SMA4F85A application, or SMA4F85A equivalent, key selection criteria include its low leakage (≤0.2 µA @ 25 °C), high-temperature reliability (Tj max = 175 °C), IEC 61000-4-2 Level 4 compliance (±25 kV contact / ±30 kV air), and SMA flat package compatibility with automated PCB assembly.
Technical Context
The SMA4F85A uses planar silicon avalanche technology to deliver precise, repeatable clamping under fast transients. Its unidirectional configuration supports DC-biased lines where reverse polarity protection is not required, and its dynamic resistance of 5.69 Ω (at 25 °C, 10/1000 µs) ensures predictable voltage rise under surge current.
Thermal performance is optimized for sustained operation: peak pulse power degrades only to 200 W at Tj = 175 °C (10/1000 µs), and thermal impedance is characterized for standard FR4 PCB footprints with 35 µm copper - supporting reliable derating in compact, thermally constrained designs.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Stand-off Voltage (VRM) | 85 V - maximum continuous reverse operating voltage before leakage exceeds 0.2 µA |
| Breakdown Voltage (VBR) | 95–105 V at 1 mA - defines onset of avalanche conduction; tight 10% tolerance enables accurate system-level margining |
| Clamping Voltage (VCL) | 137 V at 2.9 A (10/1000 µs) - limits downstream voltage stress during surge events per IEC 61000-4-2 |
| Peak Pulse Power (PPP) | 400 W (10/1000 µs) - sustains 2.9 A surge for 1 ms without failure; derates to 200 W at 175 °C junction |
| Leakage Current (IRM) | 0.2 µA at 25 °C, 1 µA at 85 °C - ensures minimal standby power loss in battery-backed or low-power sensor circuits |
| Junction Temperature Range | −55 °C to +175 °C - validated for under-hood automotive, motor drive control, and industrial power converter environments |
| ESD Robustness | ±25 kV contact / ±30 kV air (IEC 61000-4-2 Level 4) - exceeds automotive and industrial immunity requirements |
Pinout & Package
The SMA4F85A is housed in an industry-standard SMA (DO-214AC) flat package with two terminals: cathode (marked band) and anode. The matte tin-plated leads comply with J-STD-002 and support lead-free reflow per JEDEC J-STD-020 MSL level 1.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Cathode (banded end) | Surge current sink | Connected to protected line; conducts avalanche current to ground during overvoltage events |
| Anode | Reference node | Typically tied to circuit ground or lowest potential reference; completes conduction path during transient |
Key Features
| Feature | Design Value |
|---|---|
| High-temperature surge capability | Maintains 200 W (10/1000 µs) clamping performance at 175 °C junction - eliminates thermal derating concerns in sealed enclosures |
| Low-leakage planar construction | 0.2 µA IRM at 25 °C enables use in ultra-low-power IoT sensors and always-on monitoring circuits without battery drain |
| IEC 61000-4-2 Level 4 compliance | Validated for ±25 kV contact / ±30 kV air discharge - meets stringent automotive EMC requirements (e.g., ISO 10605) without external filtering |
| SMA footprint compatibility | JEDEC registered DO-214AC outline with IPC-7351 compliant land pattern - supports drop-in replacement and high-yield SMT assembly |
| Whisker-resistant plating | JESD-201 Class 2 tin finish - prevents tin whisker growth in long-life industrial and medical applications |
Applications
| Automotive Body Control Module | Industrial PLC Digital Input |
|---|---|
Use Scenario: Protecting 12 V CAN/LIN bus power rails and microcontroller I/O against load dump and ESD. IC Role / Device Role / Timing Role: Primary TVS clamp on VCC rail and signal lines; absorbs 100 ms load dump surges and sub-ns ESD pulses. Use Value: Prevents MCU reset or latch-up by limiting rail voltage to ≤137 V during 12 V system transients - eliminating need for secondary crowbar circuits. |
Use Scenario: Safeguarding 24 V digital input channels in programmable logic controllers exposed to field wiring surges. IC Role / Device Role / Timing Role: Front-end transient suppressor on optocoupler input side; clamps induced lightning surges (IEC 61000-4-5) and relay coil flyback. Use Value: Enables direct connection to unshielded field wiring while maintaining >100,000-cycle surge endurance per IEC 61000-4-2 testing. |
| DC-DC Converter Input Stage | Smart Meter Power Supply |
Use Scenario: Input-side protection for isolated 48 V–12 V buck converters in telecom infrastructure equipment. IC Role / Device Role / Timing Role: First-line defense against conducted surges entering via AC/DC front-end; placed before input filter capacitors. Use Value: Withstands repeated 400 W (10/1000 µs) surges without parameter shift - ensuring stable operation across 10+ years of field deployment. |
Use Scenario: Surge protection on 230 VAC-derived 12 V auxiliary supply in residential smart electricity meters. IC Role / Device Role / Timing Role: Secondary clamp after MOV-based primary protection; handles residual fast transients missed by bulk suppressors. Use Value: Low 5.69 Ω dynamic resistance ensures precise clamping below meter IC absolute maximum ratings - preventing firmware corruption during grid switching events. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar unidirectional TVS diode applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMAJ85A (Littelfuse) | Same VRM (85 V), but higher VBR (94–104 V) and lower PPP (400 W at 25 °C only; no 175 °C rating published) | Lacks documented 175 °C surge performance - unsuitable for under-hood or high-ambient industrial use | Select when ambient temperature stays below 125 °C and cost is prioritized over thermal margin |
| SMBJ85A (ON Semiconductor) | Same VRM, but SMB package (larger footprint); VCL = 139 V @ 2.9 A, Tj max = 150 °C (not 175 °C) | Requires PCB redesign due to SMB vs. SMA footprint; lower junction temperature limit restricts use in sealed enclosures | Choose only if existing design uses SMB layout and thermal environment is ≤150 °C |
Compared with SMAJ85A and SMBJ85A, the SMA4F85A uniquely combines 175 °C junction-rated surge capability, SMA footprint, and 5.69 Ω dynamic resistance - making it the only option qualified for high-reliability automotive and industrial applications demanding both thermal resilience and space-constrained layouts.
Availability
SMA4F85A is available at Aetrix Electronics and suitable for automotive body electronics, industrial PLC inputs, DC-DC converter input stages, and smart meter auxiliary power supplies requiring stable component supply across extended product lifecycles.
Supply support for SMA4F85A 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 and broad IP portfolio.
The SMA4F series belongs to ST's Transil™ TVS portfolio, engineered specifically for high-reliability transient suppression in harsh-environment applications where long-term stability, low leakage, and extreme temperature operation are mandatory.
FAQ
What is the maximum clamping voltage of the SMA4F85A under a 10/1000 µs surge?
The SMA4F85A clamps to a maximum of 137 V at 2.9 A under a 10/1000 µs waveform at 25 °C, as specified in Table 2 of DS12542. This value increases with junction temperature at a coefficient of 10.6 × 10⁻⁴/°C, reaching ~145 V at 175 °C.
Can the SMA4F85A be used in bidirectional signal line protection?
No - the SMA4F85A is a unidirectional TVS diode, intended only for DC-biased lines such as power rails or single-ended signals referenced to ground. For bidirectional protection (e.g., USB, RS-485), ST offers the SMA4F85AY variant or discrete back-to-back configurations.
Does the SMA4F85A meet automotive qualification standards like AEC-Q101?
While the SMA4F85A is widely used in automotive applications and rated for 175 °C operation, it is not individually AEC-Q101 qualified. ST provides AEC-Q101-qualified equivalents in the SMA6F series; consult ST's automotive-grade TVS roadmap for certified alternatives.
What is the recommended PCB footprint for optimal thermal performance?
ST specifies a JEDEC-compliant SMA footprint with minimum 1 cm² copper area per lead on FR4 (35 µm Cu), as shown in Figure 13 of DS12542. This achieves Rth(j-a) ≈ 2.5 °C/W, enabling full 400 W surge handling at 25 °C ambient and safe derating at elevated temperatures.
SMA4F85A 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):
- 85V (Max)
- Voltage - Breakdown (Min):
- 95V
- Voltage - Clamping (Max) @ Ipp:
- 137V
- Current - Peak Pulse (10/1000µs):
- 2.9A
- 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
SMA4F85A FAQ
1.How can I place an order for SMA4F85A through Aetrix?
Please submit a Request for Quotation (RFQ) for SMA4F85A 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 SMA4F85A reliable?
The price and inventory of SMA4F85A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMA4F85A is usually 5 days.
3.What payment methods are accepted for SMA4F85A?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMA4F85A transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMA4F85A?
SMA4F85A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMA4F85A 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 SMA4F85A?
For technical support, including SMA4F85A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMA4F85A requirements.
6.How does Aetrix verify that SMA4F85A is sourced from the original manufacturer or authorized distributors?
All SMA4F85A 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 SMA4F85A meets industry standards.
7.What is the process for return or replacement of SMA4F85A?
All SMA4F85A units undergo pre-shipment inspection (PSI). If there is an issue with SMA4F85A, 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 SMA4F85A part is unused and in its original packaging.
Return procedure for SMA4F85A:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SMA4F85A Tags
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