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Taiwan Semiconductor Corporation SMAJ28A
- Part No.:
- SMAJ28A
- Manufacturer:
- Taiwan Semiconductor Corporation
- Category:
- TVS Diodes
- Package:
- DO-214AC, SMA
- Datasheet:
-
SMAJ28A.pdf
- Description:
- TVS DIODE 28VWM 45.4VC DO214AC
- Quantity:
- Payment:
- Shipping:
Inventory:3,449
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Product details
Overview
SMAJ28A from Taiwan Semiconductor is a unidirectional surface-mount transient voltage suppressor (TVS) diode designed for robust overvoltage protection in DC power rails and signal lines. It features a 28 V working stand-off voltage (VWM), 31.1–34.4 V breakdown voltage (VBR), 45.4 V maximum clamping voltage (VC) at 8.8 A peak pulse current, and 400 W peak pulse power rating per 10/1000 µs waveform-ideal for protecting automotive DC/DC converters against ISO 7637-2 Pulse 1/2a/2b/3a/3b transients.
For engineers reviewing the SMAJ28A datasheet, SMAJ28A pinout, SMAJ28A application, or SMAJ28A equivalent, key selection considerations include its DO-214AC (SMA) package compatibility with automated placement, sub-1 ps response time, <1 µA reverse leakage at VWM, glass-passivated junction reliability, and compliance with J-STD-020 Level 1 moisture sensitivity and RoHS/halogen-free requirements.
Technical Context
The SMAJ28A operates as a unidirectional avalanche diode, conducting only when reverse voltage exceeds its specified breakdown range (31.1–34.4 V at 1 mA test current). Its clamping action limits transient-induced voltage to ≤45.4 V at 8.8 A, enabling effective protection of downstream 3.3 V/5 V/12 V logic and power ICs without overstressing their absolute maximum ratings.
It is rated for 150 °C maximum junction temperature, supports 40 A non-repetitive forward surge current (8.3 ms half-sine), and maintains stable performance across –55 °C to +150 °C operating and storage ranges-making it suitable for under-hood automotive, industrial SMPS, and lighting applications exposed to thermal cycling and harsh electrical environments.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VWM | 28 V - Maximum continuous reverse operating voltage before clamping begins; defines safe DC rail margin for 24 V systems. |
| VBR @ IT=1 mA | 31.1–34.4 V - Confirmed breakdown threshold ensures predictable turn-on during fast transients. |
| VC @ IPPM=8.8 A | 45.4 V - Clamped voltage under 10/1000 µs surge; guarantees protected ICs see <46 V during worst-case load dump. |
| PPPM | 400 W - Peak pulse power handling per standard 10/1000 µs waveform; sufficient for ISO 7637-2 Pulse 5a (load dump). |
| IR @ VWM | <1 µA - Ultra-low reverse leakage preserves battery life and avoids false triggering in low-power standby circuits. |
| Response Time | <1.0 ps - Sub-picosecond junction response enables suppression before ESD or fast-edge transients propagate into sensitive circuitry. |
| Package | DO-214AC (SMA) - Industry-standard surface-mount outline with 0.060 g mass, UL 94V-0 molding, and matte tin-plated leads. |
Pinout & Package
DO-214AC (SMA) package: molded plastic case with cathode band marking; anode and cathode terminals are axially aligned along the body axis. Leads are matte tin-plated, solderable per J-STD-002, and meet JESD 201 Class 2 whisker resistance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode (unmarked end) | Current return path during clamping | Connected to system ground or lower-potential rail; completes conduction loop when VREV > VBR. |
| Cathode (banded end) | Transient voltage sensing node | Connected to protected line (e.g., 24 V rail); initiates avalanche breakdown upon overvoltage detection. |
Key Features
| Feature | Design Value |
|---|---|
| Glass-passivated junction | Ensures long-term stability and low parameter drift under thermal stress and humidity exposure. |
| ISO 7637-2 compliance (Pulse 1/2a/2b/3a/3b) | Validated immunity to automotive supply-line transients including coupled noise and switch-off spikes. |
| J-STD-020 Level 1 moisture sensitivity | Enables direct placement without baking; eliminates reflow-related popcorning risk in high-volume SMT lines. |
| RoHS and halogen-free (IEC 61249-2-21) | Meets global environmental regulations for automotive and industrial end equipment without compromising ESD robustness. |
| Fast response <1 ps | Suppresses nanosecond-scale ESD events before they couple into adjacent traces or damage gate oxides. |
Applications
| Automotive DC/DC Converters | Industrial Switching Power Supplies |
|---|---|
Use Scenario: Protecting 24 V input stage of buck converter in engine control unit (ECU) subjected to ISO 7637-2 Pulse 5a load dump. IC Role / Device Role / Timing Role: Unidirectional TVS diode placed between VIN and GND to clamp transients before they reach controller IC and MOSFET gate drivers. Use Value: Limits voltage excursion to ≤45.4 V during 400 W surges, preserving 60 V-rated input capacitors and preventing controller latch-up. | Use Scenario: Input rail protection in 48 V telecom rectifier module exposed to lightning-induced surges on AC/DC front-end. IC Role / Device Role / Timing Role: Primary overvoltage clamp on bulk DC bus, coordinated with upstream MOV and downstream ceramic filters. Use Value: Delivers 400 W pulse handling with <1 µA leakage, minimizing standby power loss while maintaining fast (<1 ps) reaction to fast-rising transients. |
| LED Driver Power Inputs | On-Board Battery Management Systems |
Use Scenario: Surge protection for constant-current LED driver in streetlight fixture powered by solar-charged 24 V battery bank. IC Role / Device Role / Timing Role: Standoff-rated TVS on DC input to absorb switching transients from relay-controlled charging circuits and nearby motor loads. Use Value: 28 V VWM provides 4 V headroom above nominal 24 V, while 45.4 V VC prevents LED string overvoltage during 10/1000 µs surges. | Use Scenario: Voltage rail protection in BMS monitoring IC interface connected to 24 V vehicle battery via isolated CAN bus power domain. IC Role / Device Role / Timing Role: Localized clamping device on isolated 5 V auxiliary supply rail feeding CAN transceiver and microcontroller. Use Value: Sub-1 ps response ensures suppression occurs before transient couples through isolation barrier, safeguarding communication integrity. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient voltage suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMAJ28 | Higher clamping voltage (50.0 V vs. 45.4 V at same IPPM); identical VWM and VBR range. | Less margin for 3.3 V/5 V logic protection; acceptable where protected ICs tolerate ≥50 V transient exposure. | Select SMAJ28A when tighter clamping is required for low-voltage ICs; choose SMAJ28 if cost optimization is prioritized and system-level VC margin allows. |
| SMBJ28A | Same electrical specs but in larger DO-214AA (SMB) package; 600 W PPPM rating (vs. 400 W). | Requires PCB layout change; suited for higher-energy transients or designs needing derating headroom. | Choose SMBJ28A only if 600 W pulse capability is needed and board space permits larger footprint; SMAJ28A remains optimal for space-constrained 24 V rail protection. |
Compared with SMAJ28 and SMBJ28A, the SMAJ28A delivers the tightest clamping (45.4 V), smallest DO-214AC footprint, and best balance of surge robustness and PCB area efficiency for compact 24 V automotive and industrial modules.
Availability
SMAJ28A is available at Aetrix Electronics and suitable for automotive DC/DC converters, industrial switching power supplies, and LED driver power inputs requiring stable component supply with full traceability and lifecycle management.
Supply support for SMAJ28A 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 analog and discrete semiconductor manufacturer headquartered in Hsinchu, Taiwan, specializing in TVS diodes, rectifiers, MOSFETs, and power management devices.
The SMAJ series is part of TSC's industrial-grade transient suppression portfolio, engineered specifically for automotive and industrial applications demanding high reliability, AEC-Q200 alignment, and compliance with ISO 7637-2 and IEC 61000-4-2 standards.
FAQ
What is the maximum clamping voltage of SMAJ28A under standard 10/1000 µs surge conditions?
The SMAJ28A has a maximum clamping voltage (VC) of 45.4 V when subjected to an 8.8 A peak impulse current (IPPM) using the standardized 10/1000 µs waveform. This value is measured and guaranteed per the manufacturer's datasheet and defines the upper voltage limit imposed on protected circuitry during transient events-critical for ensuring downstream ICs remain within their absolute maximum ratings.
Is SMAJ28A suitable for bidirectional transient protection?
No, SMAJ28A is a unidirectional TVS diode intended for DC rail protection where polarity is fixed. For bidirectional applications such as AC lines or data buses, the SMAJ28CA variant (with "CA" suffix) must be used. The "A" suffix in SMAJ28A denotes tighter VBR tolerance (±5% vs. ±10% for non-A versions), not bidirectional capability.
What is the meaning of the "A" suffix in SMAJ28A?
The "A" suffix in SMAJ28A indicates a tighter breakdown voltage tolerance: 31.1–34.4 V (±5.5%) versus 31.1–38.0 V (±11%) for the standard SMAJ28. This improved consistency reduces design margin uncertainty and improves predictability in clamping behavior across production lots-especially valuable in safety-critical automotive and industrial systems.
Does SMAJ28A comply with automotive transient immunity standards?
Yes, SMAJ28A meets ISO 7637-2 requirements for Pulse 1 (inductive load disconnect), Pulse 2a (sudden load removal), Pulse 2b (supply line interruption), Pulse 3a (capacitive coupling), and Pulse 3b (ground noise). Its 400 W peak pulse power rating and fast <1 ps response make it suitable for protecting ECUs, body controllers, and ADAS modules against real-world vehicle electrical disturbances.
What is the moisture sensitivity level (MSL) rating for SMAJ28A?
SMAJ28A is rated MSL Level 1 per J-STD-020, meaning it has unlimited floor life at ≤30 °C/60% RH and can be placed directly onto PCBs without pre-baking-even after extended storage. This simplifies manufacturing logistics and eliminates yield loss from moisture-related popcorning during reflow soldering.
SMAJ28A Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Taiwan Semiconductor Corporation
- Package/Case:
- DO-214AC, SMA
- Series:
- SMAJ
- 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):
- 8.8A
- Power - Peak Pulse:
- 400W
- Power Line Protection:
- No
- Applications:
- General Purpose
- Capacitance @ Frequency:
- -
- Operating Temperature:
- -55°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- DO-214AC (SMA)
SMAJ28A FAQ
1.How can I place an order for SMAJ28A through Aetrix?
Please submit a Request for Quotation (RFQ) for SMAJ28A 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 SMAJ28A reliable?
The price and inventory of SMAJ28A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMAJ28A is usually 5 days.
3.What payment methods are accepted for SMAJ28A?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMAJ28A transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMAJ28A?
SMAJ28A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMAJ28A 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 SMAJ28A?
For technical support, including SMAJ28A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMAJ28A requirements.
6.How does Aetrix verify that SMAJ28A is sourced from the original manufacturer or authorized distributors?
All SMAJ28A 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 SMAJ28A meets industry standards.
7.What is the process for return or replacement of SMAJ28A?
All SMAJ28A units undergo pre-shipment inspection (PSI). If there is an issue with SMAJ28A, 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 SMAJ28A part is unused and in its original packaging.
Return procedure for SMAJ28A:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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