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STMicroelectronics SMA4F8.5A
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- Part No.:
- SMA4F8.5A
- Manufacturer:
- STMicroelectronics
- Category:
- TVS Diodes
- Package:
- DO-221AC, SMA Flat Leads
- Datasheet:
-
SMA4F8.5A.pdf
- Description:
- TVS DIODE 8.5VWM 19.5VC SMAFLAT
- Quantity:
- Payment:
- Shipping:
Inventory:9,967
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Product details
Overview
SMA4F8.5A 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 8.5 V stand-off voltage (VRM), 9.4–10.4 V breakdown voltage (VBR) at 1 mA, 14.4 V clamping voltage (VCL) at 27.7 A (10/1000 µs), and operates up to 175 °C junction temperature-ideal for automotive body electronics and industrial I/O protection.
For engineers reviewing the SMA4F8.5A datasheet, SMA4F8.5A pinout, SMA4F8.5A application, or SMA4F8.5A equivalent, this page delivers verified electrical characteristics, thermal derating behavior, JEDEC-standard SMA package details, and direct alternatives with documented clamping and leakage differences.
Technical Context
The SMA4F8.5A uses planar silicon avalanche technology to deliver precise, repeatable clamping under fast transients (IEC 61000-4-2 ±25 kV contact / ±30 kV air). Its low dynamic resistance (0.144 Ω at 10/1000 µs) ensures minimal voltage overshoot during high-current surges up to 27.7 A.
Thermal performance is defined by a maximum junction temperature of 175 °C and a Tj-dependent VBR/VCL shift governed by αT = 7.3 × 10⁻⁴ /°C. At elevated temperatures, clamping voltage increases linearly-critical for under-hood automotive designs where ambient exceeds 105 °C.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Stand-off Voltage (VRM) | 8.5 V - Maximum continuous reverse operating voltage before leakage exceeds 20 µA at 25 °C |
| Breakdown Voltage (VBR) | 9.4–10.4 V at 1 mA - Confirmed avalanche onset range; defines minimum trigger threshold for transient suppression |
| Clamping Voltage (VCL) | 14.4 V at 27.7 A (10/1000 µs) - Peak voltage seen by protected circuit during rated surge; determines downstream IC survivability |
| Peak Pulse Power (PPP) | 400 W (10/1000 µs) - Sustained energy handling capability at 25 °C; derates to 200 W at 175 °C junction |
| Leakage Current (IRM) | 20 µA max at VRM and 25 °C - Low standby loss critical for battery-powered sensor nodes and always-on circuits |
| Junction Temperature Range | −55 °C to +175 °C - Enables deployment in engine control units, motor drives, and industrial PLCs without thermal derating penalties |
| ESD Robustness | ±25 kV contact / ±30 kV air (IEC 61000-4-2 Level 4) - Exceeds automotive and industrial immunity requirements without external shielding |
Pinout & Package
The SMA4F8.5A is housed in a standard JEDEC DO-214AC (SMA) flat package with matte tin-plated leads, IPC7531-compliant footprint, and MSL Level 1 moisture sensitivity rating. Dimensions: 4.6 mm × 2.9 mm × 2.3 mm (L × W × H).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Cathode (marked band) | Surge current sink | Connected to protected line; conducts avalanche current to ground during overvoltage events |
| Anode | Reference/return path | Typically tied to system ground or low-impedance return plane; completes transient current loop |
Key Features
| Feature | Design Value |
|---|---|
| Low clamping ratio (VCL/VBR ≈ 1.45) | Minimizes stress on downstream 12 V-rated components during ISO 7637-2 pulse 1/2a/5a events |
| High junction temperature rating (175 °C) | Eliminates need for thermal derating in under-hood applications up to 125 °C ambient |
| 0.144 Ω dynamic resistance (RD) | Reduces voltage overshoot by <1.5 V per 10 A surge rise rate-critical for fast-edge CAN/LIN bus protection |
| UL94 V0 flammability rating | Ensures compliance with automotive interior material safety standards and industrial enclosure requirements |
Applications
| Automotive Body Control Module (BCM) | Industrial PLC Digital Input Card |
|---|---|
Use Scenario: Protecting LIN bus transceivers and microcontroller GPIOs from load dump and alternator ripple-induced spikes. IC Role / Device Role / Timing Role: Primary unidirectional TVS clamp placed directly at connector entry point, upstream of ESD diodes and filtering RC networks. Use Value: Clamps 100 V/10 ms load dump transients to ≤14.4 V, preventing latch-up or permanent damage to 5 V/3.3 V logic interfaces. | Use Scenario: Safeguarding 24 V digital input channels against field-wiring induced surges and inductive kickback from solenoid valves. IC Role / Device Role / Timing Role: Standoff-rated TVS device mounted adjacent to terminal block, providing first-line defense before optocoupler isolation stage. Use Value: Withstands repeated 1 kV/500 A surge events (IEC 61000-4-5) while maintaining <20 µA leakage at 24 V nominal-preserving input threshold accuracy. |
| Smart Meter Power Supply Rail | Telecom Remote Terminal Unit (RTU) |
Use Scenario: Securing AC/DC converter output rails against lightning-induced surges entering via mains or neutral lines. IC Role / Device Role / Timing Role: Secondary surge suppressor located after MOV and fuse, delivering precise low-voltage clamping for downstream LDOs and metering ICs. Use Value: Limits rail excursion to 14.4 V during 400 W transients, avoiding brownout resets and flash memory corruption in metrology SoCs. | Use Scenario: Shielding RS-485 communication ports in outdoor RTUs exposed to induced surges from nearby lightning strikes. IC Role / Device Role / Timing Role: Unidirectional TVS placed on A/B differential lines, referenced to local ground, with matched layout to preserve common-mode rejection. Use Value: Maintains signal integrity by clamping differential surges to <15 V while adding <0.5 pF capacitance-no data rate degradation at 10 Mbps. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar unidirectional TVS diode applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMAJ8.5A (Littelfuse) | VBR = 9.4–10.4 V (same), but VCL = 15.0 V @ 26.7 A (10/1000 µs); higher RD = 0.16 Ω | Marginally higher clamping degrades protection margin for 12 V systems with tight voltage tolerances | Prefer SMA4F8.5A when protecting 12 V logic or automotive sensors requiring lowest possible VCL |
| P6SMB8.5A (ON Semiconductor) | VBR = 9.0–10.0 V; VCL = 14.4 V @ 27.8 A (10/1000 µs); same clamping but 600 W rating (10/1000 µs) | Higher peak power allows single-device coverage across wider surge severity classes (e.g., IEC 61000-4-5 Level 4) | Select P6SMB8.5A only if system-level testing requires >400 W surge margin; otherwise SMA4F8.5A offers superior thermal stability at 175 °C |
Compared with SMAJ8.5A and P6SMB8.5A, the SMA4F8.5A delivers identical clamping performance to the latter but with guaranteed 175 °C operation and lower leakage-making it optimal for thermally constrained, long-lifetime automotive and industrial deployments where reliability trumps raw power headroom.
Availability
SMA4F8.5A is available at Aetrix Electronics and suitable for automotive body electronics, industrial PLC I/O modules, smart meter power supplies, and telecom RTU interface protection requiring stable component supply and full traceability.
Supply support for SMA4F8.5A 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 analog/mixed-signal IP.
The SMA4F series belongs to ST's Transil™ TVS portfolio, engineered specifically for high-reliability transient suppression in harsh environments-emphasizing low leakage, high-temperature stability, and precise clamping for next-generation automotive and industrial control systems.
FAQ
What is the maximum allowable surge current for SMA4F8.5A under IEC 61000-4-2 conditions?
The SMA4F8.5A withstands ±25 kV contact and ±30 kV air discharge per IEC 61000-4-2 Level 4. Its peak pulse current is 27.7 A (10/1000 µs) and 124 A (8/20 µs), validated at 25 °C ambient. Derating applies above 25 °C junction temperature per Figure 3 in DS12542.
Does SMA4F8.5A require heatsinking in typical PCB layouts?
No dedicated heatsink is required. The SMA package achieves Rth(j-a) ≈ 120 °C/W on a standard FR4 board with 1 cm² copper per lead (Figure 11). At 400 W surge, junction temperature rise is transient (<10 ms) and self-limiting-thermal design focuses on layout copper area, not external heatsinks.
How does leakage current change with temperature for SMA4F8.5A?
At VRM = 8.5 V, leakage is ≤20 µA at 25 °C and ≤50 µA at 85 °C (Table 2). Figure 8 shows IR rises exponentially with Tj-reaching ~1000 nA (~1 µA) at 125 °C and ~10,000 nA (~10 µA) at 175 °C. This remains well below 100 µA even at max Tj.
Can SMA4F8.5A be used in bidirectional configurations?
No. SMA4F8.5A is unidirectional (Type A), with cathode marking indicating polarity-sensitive placement. For bidirectional protection, ST offers the SMA4F8.5CA variant (center-tapped, symmetrical clamping), which is a distinct part number-not a pin-compatible substitute.
SMA4F8.5A 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):
- 8.5V
- Voltage - Breakdown (Min):
- 9.4V
- Voltage - Clamping (Max) @ Ipp:
- 19.5V
- Current - Peak Pulse (10/1000µs):
- 27.7A
- 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
SMA4F8.5A FAQ
1.How can I place an order for SMA4F8.5A through Aetrix?
Please submit a Request for Quotation (RFQ) for SMA4F8.5A 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 SMA4F8.5A reliable?
The price and inventory of SMA4F8.5A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMA4F8.5A is usually 5 days.
3.What payment methods are accepted for SMA4F8.5A?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMA4F8.5A transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMA4F8.5A?
SMA4F8.5A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMA4F8.5A 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 SMA4F8.5A?
For technical support, including SMA4F8.5A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMA4F8.5A requirements.
6.How does Aetrix verify that SMA4F8.5A is sourced from the original manufacturer or authorized distributors?
All SMA4F8.5A 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 SMA4F8.5A meets industry standards.
7.What is the process for return or replacement of SMA4F8.5A?
All SMA4F8.5A units undergo pre-shipment inspection (PSI). If there is an issue with SMA4F8.5A, 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 SMA4F8.5A part is unused and in its original packaging.
Return procedure for SMA4F8.5A:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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