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Taiwan Semiconductor Corporation SMF40A
- Part No.:
- SMF40A
- Manufacturer:
- Taiwan Semiconductor Corporation
- Category:
- TVS Diodes
- Package:
- SOD-123W
- Datasheet:
-
SMF40A.pdf
- Description:
- TVS DIODE 40VWM 64.5VC SOD123W
- Quantity:
- Payment:
- Shipping:
Inventory:8,179
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Product details
Overview
SMF40A from Taiwan Semiconductor is a unidirectional surface-mount transient voltage suppressor (TVS) diode designed for high-energy ESD and surge protection in DC power rails and signal lines. It features a 40 V working stand-off voltage (VWM), 44.4–49.1 V breakdown voltage (VBR), 64.5 V clamping voltage (VC) at 3.1 A peak pulse current, and 200 W peak pulse power (10/1000 µs waveform), making it suitable for automotive load-dump and industrial I/O interface protection.
For engineers reviewing the SMF40A datasheet, SMF40A pinout, SMF40A application, or SMF40A equivalent, key selection criteria include clamping performance under ISO 7637-2 Pulse 1/2a/2b/3a/3b, low leakage (<1 µA above 10 V), SOD-123W package compatibility with automated placement, and thermal resistance (RθJL = 33 °C/W) for PCB-level thermal management.
Technical Context
The SMF40A operates as a unidirectional avalanche diode, triggered when reverse voltage exceeds its specified breakdown range (44.4–49.1 V at 1 mA test current). Its clamping action limits transient voltages to ≤64.5 V at 3.1 A (10/1000 µs), delivering robust protection against fast electrical transients without forward conduction during normal operation.
It meets ISO 7637-2 immunity requirements for automotive electronics and supports reliable operation across –55 °C to +175 °C junction temperature range. The device uses a glass-passivated junction for stable leakage performance and moisture sensitivity level 1 (per J-STD-020), enabling standard reflow assembly without dry-pack handling.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VWM | 40 V - Maximum continuous reverse operating voltage before clamping begins |
| VBR min/max | 44.4 V / 49.1 V - Breakdown occurs within this range at 1 mA, defining turn-on threshold tolerance |
| VC @ IPPM | 64.5 V - Clamped voltage seen by protected circuit during 3.1 A 10/1000 µs surge |
| PPPM | 200 W - Peak transient energy absorption capability under standardized surge waveform |
| IR @ VWM | <1 µA - Negligible leakage current at rated stand-off voltage, minimizing standby power loss |
| RθJL | 33 °C/W - Junction-to-lead thermal resistance enables efficient heat transfer to PCB copper pad |
| Package | SOD-123W - Surface-mount outline with matte tin-plated leads, UL 94V-0 molding compound |
Pinout & Package
SOD-123W is a compact, single-diode surface-mount package with cathode-indicating band marking. Leads are matte tin-plated and solderable per J-STD-002; polarity is unambiguous via visible cathode band.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Forward current entry / Reverse surge return path | Connected to lower-potential side (e.g., GND or return rail) in unidirectional TVS configuration |
| Cathode | Reverse-biased terminal / Surge shunt node | Connected to protected line (e.g., 40 V supply rail); conducts avalanche current during overvoltage events |
Key Features
| Feature | Design Value |
|---|---|
| Glass-passivated junction | Ensures stable VBR tolerance and low IR drift over temperature and lifetime |
| ISO 7637-2 compliance | Validated for Pulse 1 (inductive load dump), Pulse 2a/2b (battery disconnect), and Pulse 3a/3b (switching transients) |
| Moisture sensitivity level 1 | Eliminates bake requirements prior to reflow; compatible with standard SMT assembly lines |
| UL 94V-0 molding compound | Provides flame-retardant encapsulation required for automotive and industrial safety certifications |
Applications
| Automotive Power Rail Protection | Industrial Sensor Interface Protection |
|---|---|
Use Scenario: Protecting 12 V/24 V battery-fed ECUs from load-dump spikes and alternator transients. IC Role / Device Role / Timing Role: Unidirectional TVS placed between power rail and ground to clamp surges before they reach downstream regulators and microcontrollers. Use Value: Limits transient voltage to ≤64.5 V while absorbing 200 W pulses, preserving system uptime and component reliability per ISO 16750-2. | Use Scenario: Shielding analog sensor inputs (e.g., pressure, temperature) from EFT and ESD coupling on long cables. IC Role / Device Role / Timing Role: Low-capacitance TVS mounted at connector entry point to divert fast transients away from precision ADC front-ends. Use Value: Sub-1 µA leakage at 40 V ensures minimal signal offset error; SOD-123W footprint allows placement adjacent to I/O connectors without board area penalty. |
| LED Driver Output Protection | RS-485 Transceiver Bus Line Protection |
Use Scenario: Safeguarding constant-current LED driver outputs against inductive kickback from disconnected loads. IC Role / Device Role / Timing Role: TVS connected across output terminals to clamp reverse-recovery spikes generated by inductive ballast elements. Use Value: 64.5 V clamping prevents gate oxide damage to MOSFET drivers; 33 °C/W RθJL supports sustained surge duty in enclosed luminaires. | Use Scenario: Hardening RS-485 differential bus lines (A/B) against lightning-induced surges and hot-plug transients. IC Role / Device Role / Timing Role: One SMF40A per line (A-to-GND, B-to-GND) providing symmetric unidirectional clamping referenced to local ground. Use Value: Matches common-mode surge immunity requirements of IEC 61000-4-5 Level 3; SOD-123W allows dual-device placement within tight 8 mm spacing constraints. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient voltage suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMAJ40A (onsemi) | Same VWM (40 V), slightly higher VC (69.4 V @ 2.9 A), identical SOD-123 package | Higher clamping voltage reduces margin for 48 V systems near absolute maximum ratings | Select SMAJ40A only if legacy design validation exists; verify clamping headroom with actual surge profile |
| P6SMB40A (Littelfuse) | Same VWM (40 V), same VC (64.5 V), but larger DO-214AA (SMB) package and 600 W PPPM rating | Requires PCB layout change; suited for higher-energy transients where 200 W is insufficient | Choose P6SMB40A when surge energy exceeds 200 W or thermal mass demands larger package |
Compared with SMAJ40A and P6SMB40A, the SMF40A offers optimal balance of compact SOD-123W footprint, precise 64.5 V clamping, and ISO 7637-2 qualification-making it preferred for space-constrained automotive and industrial modules where layout reuse and standardized test compliance are critical.
Availability
SMF40A is available at Aetrix Electronics and suitable for automotive ECU protection, industrial sensor interface hardening, and LED driver output safeguarding requiring stable component supply and full traceability.
Supply support for SMF40A 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
Taiwan Semiconductor Corporation (TSC) is a vertically integrated semiconductor manufacturer specializing in discrete power devices, TVS diodes, rectifiers, and MOSFETs for automotive, industrial, and consumer markets.
The SMF series was developed specifically for high-reliability, surface-mount transient suppression in harsh environments-emphasizing ISO 7637-2 compliance, low leakage, and automated assembly readiness.
FAQ
What is the maximum clamping voltage of the SMF40A under standard surge conditions?
The SMF40A exhibits a maximum clamping voltage (VC) of 64.5 V when subjected to a 10/1000 µs surge waveform at its rated peak pulse current of 3.1 A. This value is measured per JEDEC standards and confirmed in the official Taiwan Semiconductor datasheet (Version D2103, Page 3). The clamping performance ensures protected circuits remain below critical voltage thresholds during real-world transients such as load dump or EFT events.
Is the SMF40A suitable for bidirectional transient protection?
No, the SMF40A is a unidirectional TVS diode and is not rated for bidirectional operation. Its electrical specifications-including breakdown voltage, clamping behavior, and test methodology-are defined only for reverse-bias (cathode-positive) conditions. For bidirectional protection, engineers must select a dedicated bidirectional variant such as SMF40CA or use back-to-back unidirectional devices; using SMF40A in AC or floating applications risks failure or inadequate clamping.
Does the SMF40A meet automotive qualification standards beyond ISO 7637-2?
Yes, the SMF40A meets ISO 7637-2 Pulse 1, 2a, 2b, 3a, and 3b requirements as explicitly stated in the Taiwan Semiconductor datasheet. While it is not AEC-Q200 qualified as a standalone component, its construction-including glass-passivated junction, MSL Level 1 rating, and –55 °C to +175 °C operating range-supports integration into AEC-Q200-compliant systems when validated at the module level per customer requirements.
What is the thermal resistance from junction to ambient for the SMF40A in standard mounting conditions?
The SMF40A has a junction-to-ambient thermal resistance (RθJA) of 100 °C/W when mounted on a 5 mm × 5 mm copper pad on FR-4 PCB, per the thermal performance table in the Taiwan Semiconductor datasheet (Version D2103, Page 2). This value assumes still air conditions and is used to estimate steady-state temperature rise under continuous power dissipation-though the device is intended for transient, not continuous, power handling.
Can the SMF40A be used in place of the SMAJ40A without layout changes?
Yes, the SMF40A and SMAJ40A share identical SOD-123 package dimensions and pinout, enabling direct PCB footprint compatibility. However, engineers must verify that the lower clamping voltage of SMF40A (64.5 V vs. SMAJ40A's 69.4 V) provides sufficient margin for their specific surge profile and downstream IC absolute maximum ratings before substitution.
SMF40A Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Taiwan Semiconductor Corporation
- Package/Case:
- SOD-123W
- Series:
- SMF
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Type:
- Zener
- Unidirectional Channels:
- 1
- Bidirectional Channels:
- -
- Voltage - Reverse Standoff (Typ):
- 40V
- Voltage - Breakdown (Min):
- 44.4V
- Voltage - Clamping (Max) @ Ipp:
- 64.5V
- Current - Peak Pulse (10/1000µs):
- 3.1A
- Power - Peak Pulse:
- 200W
- 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:
- SOD-123W
SMF40A FAQ
1.How can I place an order for SMF40A through Aetrix?
Please submit a Request for Quotation (RFQ) for SMF40A 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 SMF40A reliable?
The price and inventory of SMF40A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMF40A is usually 5 days.
3.What payment methods are accepted for SMF40A?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMF40A transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMF40A?
SMF40A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMF40A 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 SMF40A?
For technical support, including SMF40A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMF40A requirements.
6.How does Aetrix verify that SMF40A is sourced from the original manufacturer or authorized distributors?
All SMF40A 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 SMF40A meets industry standards.
7.What is the process for return or replacement of SMF40A?
All SMF40A units undergo pre-shipment inspection (PSI). If there is an issue with SMF40A, 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 SMF40A part is unused and in its original packaging.
Return procedure for SMF40A:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SMF40A Tags
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