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Taiwan Semiconductor Corporation SMF28A
- Part No.:
- SMF28A
- Manufacturer:
- Taiwan Semiconductor Corporation
- Category:
- TVS Diodes
- Package:
- SOD-123W
- Datasheet:
-
SMF28A.pdf
- Description:
- TVS DIODE 28VWM 45.4VC SOD123W
- Quantity:
- Payment:
- Shipping:
Inventory:4,535
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Product details
Overview
SMF28A from Taiwan Semiconductor is a unidirectional surface-mount transient voltage suppressor (TVS) diode designed for high-energy surge protection in DC power lines and signal paths. It features a 28 V working stand-off voltage (VWM), 31.1–34.4 V breakdown voltage (VBR), 45.4 V clamping voltage (VC) at 4.4 A peak pulse current, and 200 W peak pulse power (10/1000 µs waveform). It is used in automotive ECU power rail protection and industrial sensor interface circuits.
For engineers reviewing the SMF28A datasheet, SMF28A pinout, SMF28A application, or SMF28A 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 junction temperature range of –55 °C to +175 °C.
Technical Context
The SMF28A operates as a unidirectional avalanche diode, triggered when reverse voltage exceeds its specified breakdown threshold (VBR = 31.1–34.4 V). Its clamping action limits transient-induced voltage spikes to ≤45.4 V at 4.4 A, protecting downstream ICs such as microcontrollers and CAN transceivers.
It meets ISO 7637-2 immunity requirements for automotive electronics and is rated for 200 W peak pulse power (10/1000 µs), with thermal resistance RθJL = 33 °C/W and RθJA = 100 °C/W on a 5 mm × 5 mm PCB copper pad. The device uses glass-passivated junction technology for stable, low-leakage performance.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VWM | 28 V - Maximum continuous reverse operating voltage before clamping begins |
| VBR @ IT=1 mA | 31.1–34.4 V - Breakdown voltage range defining reliable avalanche onset |
| VC @ IPPM=4.4 A | 45.4 V - Clamped voltage during 10/1000 µs surge, limiting stress on protected ICs |
| PPPM | 200 W - Peak pulse power handling per IEC 61000-4-5 / ISO 7637-2 standards |
| IR @ VWM | <1 µA - Ultra-low reverse leakage ensures minimal standby power loss |
| TJ Range | –55 °C to +175 °C - Enables use in under-hood automotive and industrial environments |
Pinout & Package
Package: SOD-123W - Surface-mount plastic case with matte tin-plated leads, UL 94V-0 rated molding compound, polarity indicated by cathode band, weight ≈ 0.016 g.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Forward conduction terminal | Connected to lower-potential side (e.g., GND or return path) in unidirectional configuration |
| Cathode | Reverse-biased clamping terminal | Connected to protected line (e.g., 24 V supply rail); conducts during overvoltage events |
Key Features
| Feature | Design Value |
|---|---|
| Glass-passivated junction | Ensures stable VBR tolerance and long-term reliability under thermal cycling |
| Low IR <1 µA @ VWM | Minimizes quiescent current draw in always-on systems like automotive body controllers |
| ISO 7637-2 compliance | Validated for Pulse 1 (inductive load dump), Pulse 2a/2b (switching transients), and Pulse 3a/3b (ESD-like fast transients) |
| SOD-123W footprint | Enables high-density PCB layout and compatibility with standard pick-and-place equipment |
Applications
| Automotive Power Rail Protection | Industrial Sensor Interface |
|---|---|
Use Scenario: Protecting 24 V supply inputs of engine control units against load dump and inductive switching transients. IC Role / Device Role / Timing Role: Unidirectional TVS diode placed between power rail and ground to clamp surges before they reach MCU power pins. Use Value: Limits transient voltage to ≤45.4 V, preventing latch-up or permanent damage to 3.3 V/5 V logic supplies downstream. | Use Scenario: Safeguarding analog front-end inputs of pressure or temperature sensors connected to long cables in factory automation. IC Role / Device Role / Timing Role: Reverse-biased clamping element on signal line to absorb EFT bursts and cable-coupled noise. Use Value: Maintains signal integrity by suppressing transients up to 200 W without adding capacitance that degrades bandwidth. |
| LED Driver Output Protection | RS-485 Transceiver Line Protection |
Use Scenario: Shielding constant-current LED driver outputs from voltage spikes caused by hot-plug or cable disconnect events. IC Role / Device Role / Timing Role: Unidirectional TVS placed across output terminals to shunt surge energy to ground. Use Value: Prevents overvoltage failure of external MOSFETs or LED strings while maintaining low leakage in steady state. | Use Scenario: Adding robustness to RS-485 bus lines exposed to lightning-induced surges or ground potential differences. IC Role / Device Role / Timing Role: Bidirectional-capable protection (used unidirectionally here) on A/B differential lines referenced to local ground. Use Value: Clamps common-mode transients to safe levels without distorting differential signaling due to low junction capacitance. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient voltage suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMAJ28A | Same VWM (28 V), but higher VC = 48.4 V; SOD-123 package (not SOD-123W); lower PPPM = 400 W (but derated to ~175 W at TJ > 25°C) | Less effective clamping margin for sensitive 3.3 V logic; requires revalidation of PCB thermal relief | Prefer SMF28A where tighter clamping and verified ISO 7637-2 compliance are required |
| P6SMB28A | Higher VWM = 28 V, but larger DO-214AA package; VC = 45.7 V; same 200 W rating; higher IR (~5 µA) | Not suitable for space-constrained layouts; may require board redesign due to footprint mismatch | Choose SMF28A for SMT density and automated assembly; P6SMB28A only if legacy DO-214AA is mandated |
Compared with SMAJ28A and P6SMB28A, the SMF28A delivers superior clamping precision (45.4 V vs. ≥45.7 V), lower leakage, and optimized thermal performance in the compact SOD-123W package-making it preferred for next-generation automotive and industrial modules where board area and surge margin are critical.
Availability
SMF28A is available at Aetrix Electronics and suitable for automotive ECUs, industrial sensor nodes, LED lighting drivers, and RS-485 communication interfaces requiring stable component supply and full traceability.
Supply support for SMF28A 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 SMF28A belongs to TSC's SMF series of surface-mount TVS diodes engineered specifically for high-reliability transient suppression in harsh environments-emphasizing low clamping voltage, ISO 7637-2 compliance, and robust thermal performance.
FAQ
What is the maximum clamping voltage of the SMF28A under standard test conditions?
The SMF28A has a maximum clamping voltage (VC) of 45.4 V when subjected to a 10/1000 µs peak pulse current of 4.4 A. This value is measured at TA = 25 °C and defines the upper voltage limit imposed on protected circuitry during surge events. The SMF28A maintains this clamping performance across its qualified operating temperature range, making it suitable for automotive and industrial applications where voltage margin is critical.
Does the SMF28A meet automotive surge immunity standards?
Yes, the SMF28A meets ISO 7637-2 requirements for Pulse 1 (inductive load dump), Pulse 2a/2b (switching transients), and Pulse 3a/3b (fast EFT events). Its 200 W peak pulse power rating, low clamping voltage, and glass-passivated junction ensure consistent performance under repeated surge stress-key for automotive power rail protection where the SMF28A is commonly deployed.
What is the package type and mounting compatibility of the SMF28A?
The SMF28A uses the SOD-123W surface-mount package with matte tin-plated leads compliant with J-STD-002 solderability standards. Its dimensions and pad layout align with IPC-7351 recommendations, enabling seamless integration into automated SMT lines. The SOD-123W footprint is slightly wider than standard SOD-123, improving thermal dissipation-critical for sustained surge handling in the SMF28A.
How does the SMF28A compare to the SMF24A in terms of voltage ratings?
The SMF28A has a working stand-off voltage (VWM) of 28 V and breakdown voltage (VBR) of 31.1–34.4 V, whereas the SMF24A offers VWM = 24 V and VBR = 26.7–29.5 V. Both share identical package, thermal specs, and surge capability-but the SMF28A is selected for 24 V nominal systems requiring higher margin against ripple and tolerance drift, while the SMF24A suits tighter 20–24 V rails where lower VBR improves response speed.
Is the SMF28A RoHS and halogen-free compliant?
Yes, the SMF28A is RoHS compliant and halogen-free per IEC 61249-2-21. It also meets moisture sensitivity level (MSL) 1 per J-STD-020, meaning it can be stored indefinitely at ambient conditions without baking prior to reflow. These qualifications support use in environmentally regulated industries including automotive and medical-adjacent equipment where material compliance is mandatory.
SMF28A 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):
- 28V
- Voltage - Breakdown (Min):
- 31.1V
- Voltage - Clamping (Max) @ Ipp:
- 45.4V
- Current - Peak Pulse (10/1000µs):
- 4.4A
- 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
SMF28A FAQ
1.How can I place an order for SMF28A through Aetrix?
Please submit a Request for Quotation (RFQ) for SMF28A 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 SMF28A reliable?
The price and inventory of SMF28A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMF28A is usually 5 days.
3.What payment methods are accepted for SMF28A?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMF28A transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMF28A?
SMF28A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMF28A 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 SMF28A?
For technical support, including SMF28A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMF28A requirements.
6.How does Aetrix verify that SMF28A is sourced from the original manufacturer or authorized distributors?
All SMF28A 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 SMF28A meets industry standards.
7.What is the process for return or replacement of SMF28A?
All SMF28A units undergo pre-shipment inspection (PSI). If there is an issue with SMF28A, 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 SMF28A part is unused and in its original packaging.
Return procedure for SMF28A:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SMF28A Tags
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