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Taiwan Semiconductor Corporation SMAJ40A
- Part No.:
- SMAJ40A
- Manufacturer:
- Taiwan Semiconductor Corporation
- Category:
- TVS Diodes
- Package:
- DO-214AC, SMA
- Datasheet:
-
SMAJ40A.pdf
- Description:
- TVS DIODE 40VWM 64.5VC DO214AC
- Quantity:
- Payment:
- Shipping:
Inventory:6,155
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Product details
Overview
SMAJ40A from Taiwan Semiconductor is a unidirectional surface-mount transient voltage suppressor (TVS) diode in DO-214AC (SMA) package, designed for robust overvoltage protection in DC power rails. It features a 40 V working stand-off voltage (VWM), 44.4–49.1 V breakdown voltage (VBR), 64.5 V maximum clamping voltage (VC) at 6.2 A peak pulse current, and 400 W peak pulse power rating with 10/1000 µs waveform.
For engineers reviewing the SMAJ40A datasheet, SMAJ40A pinout, SMAJ40A application, or SMAJ40A equivalent, key selection considerations include its unidirectional polarity, low clamping ratio (VC/VBR ≈ 1.31), compliance with ISO 7637-2 Pulse 1/2a/2b/3a/3b, and suitability for automotive and industrial DC/DC converter input protection where fast response (<1 ps) and <1 µA leakage above 10 V are critical.
Technical Context
The SMAJ40A operates as a unidirectional avalanche diode, triggered when reverse voltage exceeds its specified VBR range (44.4–49.1 V at 1 mA test current). Its glass-passivated junction ensures stable breakdown characteristics and low leakage (≤1 µA at 40 V), while its DO-214AC package supports automated placement and meets J-STD-020 moisture sensitivity level 1.
It delivers 400 W peak pulse power under 10/1000 µs waveform up to 25 °C, derating linearly above that ambient temperature per Fig.2. The device sustains 40 A non-repetitive forward surge current (IFSM) and exhibits a maximum forward voltage of 3.5 V at 25 A - critical for bidirectional surge paths when used with external rectification or in clamp-to-rail configurations.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VWM | 40 V - Maximum continuous reverse operating voltage before significant leakage; defines safe DC rail margin. |
| VBR min/max | 44.4 V / 49.1 V @ 1 mA - Tight breakdown window ensures predictable turn-on across production lots. |
| VC @ IPPM | 64.5 V @ 6.2 A - Clamping voltage during 10/1000 µs transient; limits downstream IC stress to ≤64.5 V. |
| PPPM | 400 W (10/1000 µs) - Peak surge energy handling capacity; sufficient for ISO 7637-2 Pulse 1 (inductive load dump). |
| IR @ VWM | ≤1 µA - Ultra-low leakage preserves battery life and avoids false triggering in high-impedance sensing circuits. |
| TJ max | 150 °C - Enables operation in under-hood automotive environments and enclosed industrial enclosures. |
| Package | DO-214AC (SMA) - Standardized surface-mount outline compatible with IPC-7351B land patterns; 0.060 g weight aids thermal mass management. |
Pinout & Package
DO-214AC (SMA) package: molded plastic case with matte tin-plated leads, cathode band marking polarity, UL 94V-0 rated compound, and JESD201 Class 2 whisker resistance. Weight: 0.060 g.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode (unmarked end) | Forward conduction terminal | Connected to protected line (e.g., +12 V rail); conducts during positive transients when used in reverse-biased clamp configuration. |
| Cathode (banded end) | Reverse breakdown terminal | Connected to ground or lower-potential reference; initiates avalanche conduction when reverse voltage exceeds VBR. |
Key Features
| Feature | Design Value |
|---|---|
| Glass-passivated junction | Ensures stable VBR tolerance and long-term reliability under thermal cycling and humidity exposure. |
| Fast response time <1.0 ps | Clamps ESD and lightning-induced transients before sensitive downstream circuitry is damaged. |
| ISO 7637-2 compliance (Pulse 1/2a/2b/3a/3b) | Validated for automotive 12 V system immunity, including load dump (Pulse 5a not covered - requires higher-voltage variant). |
| RoHS & halogen-free | Meets IEC 61249-2-21 and EU RoHS Directive 2011/65/EU for environmentally constrained applications. |
| Moisture sensitivity level 1 | Zero bake requirement prior to reflow; supports standard SMT assembly without floor-life restrictions. |
Applications
| Switching Mode Power Supply (SMPS) Input Protection | Automotive On-Board DC/DC Converter |
|---|---|
Use Scenario: Protects primary-side rectifier output and controller ICs against line surges and inductive switching spikes in offline AC/DC adapters and isolated DC/DC modules. IC Role / Device Role / Timing Role: Unidirectional TVS placed between rectified DC bus and ground, clamping transients within 1 ps to limit voltage excursion to ≤64.5 V. Use Value: Prevents MOSFET gate oxide rupture and controller latch-up by holding rail voltage below 65 V during 400 W 10/1000 µs events. | Use Scenario: Shields 12 V → 3.3 V/5 V buck converter inputs in automotive body control modules (BCMs) and infotainment systems exposed to load dump and jump-start conditions. IC Role / Device Role / Timing Role: Standoff-rated TVS on VIN pin, activated only during overvoltage events exceeding 40 V, with minimal standby leakage. Use Value: Maintains system uptime by surviving ISO 7637-2 Pulse 1 (−150 V, 50 ms) and Pulse 2b (−100 V, 100 ms) without degradation. |
| Industrial Lighting Driver Input Stage | Industrial Adapter Secondary-Side Rail Protection |
Use Scenario: Safeguards constant-current LED driver ICs from voltage reversals and capacitor discharge transients in streetlight and high-bay lighting systems. IC Role / Device Role / Timing Role: Unidirectional clamp referenced to system ground, absorbing negative-going spikes induced by relay coil de-energization. Use Value: Eliminates need for series fusing in low-power drivers due to 400 W surge rating and 150 °C junction capability. | Use Scenario: Secures secondary-side 24 V output rails in medical and industrial wall adapters subjected to mains-borne surges and hot-plug events. IC Role / Device Role / Timing Role: TVS placed across output terminals to clamp both differential-mode and common-mode overvoltages. Use Value: Achieves IEC 61000-4-5 Level 3 (1 kV line-earth) immunity with single-device solution and no additional filtering. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient voltage suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMAJ40CA | Bidirectional version; symmetric VBR (44.4–49.1 V) in both directions; same VC (64.5 V) and PPPM (400 W). | Required for AC-coupled lines or bidirectional data/power buses where polarity reversal occurs. | Select SMAJ40CA only if protection is needed against both positive and negative transients - SMAJ40A is optimal for DC rails with defined polarity. |
| SMBJ40A | Same electrical specs but in larger DO-214AA (SMB) package; 600 W PPPM rating (10/1000 µs); higher IFSM (100 A). | Preferred in high-energy environments (e.g., heavy-duty motor drives) where PCB space allows larger footprint. | Choose SMBJ40A when surge energy exceeds 400 W or when enhanced thermal dissipation is required; SMAJ40A fits tighter layouts. |
Compared with SMAJ40CA and SMBJ40A, the SMAJ40A offers the smallest footprint for unidirectional 40 V rail protection, with verified 1 µA leakage and ISO 7637-2 compliance - making it ideal for space-constrained automotive and industrial DC/DC designs where polarity is fixed and peak energy stays within 400 W.
Availability
SMAJ40A is available at Aetrix Electronics and suitable for switching mode power supplies, automotive DC/DC converters, and industrial lighting drivers requiring stable component supply with full traceability and lifecycle support.
Supply support for SMAJ40A 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, serving global automotive, industrial, and consumer markets since 1979.
The SMAJ series is part of TSC's transient voltage suppression portfolio, engineered specifically for high-reliability DC rail protection in harsh electromagnetic environments - emphasizing low clamping ratio, fast response, and AEC-Q200 readiness for automotive-grade use.
FAQ
What is the polarity configuration of the SMAJ40A?
The SMAJ40A is a unidirectional TVS diode, with cathode indicated by a band on the DO-214AC package. It conducts in forward bias and clamps in reverse bias above its breakdown voltage. This configuration is intended for DC power rail protection where polarity is fixed - unlike bidirectional variants such as SMAJ40CA. The SMAJ40A must be oriented with cathode toward the protected rail's higher potential to function correctly.
Does the SMAJ40A meet automotive EMC standards?
Yes, the SMAJ40A meets ISO 7637-2 requirements for Pulse 1 (inductive load dump), Pulse 2a (sudden load removal), Pulse 2b (supply interruption), Pulse 3a (capacitive coupled transients), and Pulse 3b (inductive coupled transients). It is widely deployed in automotive BCMs and infotainment systems. Note that ISO 7637-2 Pulse 5a (load dump with alternator regulation) requires higher-voltage variants (e.g., SMAJ64A or above) due to its ±150 V amplitude.
What is the maximum clamping voltage of the SMAJ40A under standard test conditions?
The SMAJ40A has a maximum clamping voltage (VC) of 64.5 V at 6.2 A peak pulse current, tested with a 10/1000 µs waveform. This value is measured at TJ = 25 °C and represents the upper limit of voltage seen by downstream circuitry during a worst-case transient. The clamping ratio (VC/VBR) is approximately 1.31, confirming efficient energy diversion with minimal overvoltage overshoot.
Can the SMAJ40A be used in bidirectional signal line protection?
No - the SMAJ40A is strictly unidirectional and unsuitable for bidirectional signal lines such as RS-485, CAN, or USB data pairs. For those applications, a bidirectional TVS like SMAJ40CA or dedicated signal-line suppressors (e.g., SP3012-02UTG) are required. Using SMAJ40A on AC or polarity-agnostic lines risks failure during negative excursions, as it lacks reverse conduction capability beyond its forward voltage drop.
What is the thermal derating behavior of the SMAJ40A above 25°C ambient?
The SMAJ40A's peak pulse power (PPPM) derates linearly above TA = 25 °C, per Figure 2 in the official datasheet. At 75 °C ambient, its PPPM drops to ~300 W; at 125 °C, it falls to ~150 W. This derating must be factored into system-level thermal design - especially in enclosed automotive or industrial enclosures - to ensure the device remains within safe SOA during repeated surge events.
SMAJ40A 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):
- 40V
- Voltage - Breakdown (Min):
- 44.4V
- Voltage - Clamping (Max) @ Ipp:
- 64.5V
- Current - Peak Pulse (10/1000µs):
- 6.2A
- 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)
SMAJ40A FAQ
1.How can I place an order for SMAJ40A through Aetrix?
Please submit a Request for Quotation (RFQ) for SMAJ40A 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 SMAJ40A reliable?
The price and inventory of SMAJ40A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMAJ40A is usually 5 days.
3.What payment methods are accepted for SMAJ40A?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMAJ40A transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMAJ40A?
SMAJ40A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMAJ40A 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 SMAJ40A?
For technical support, including SMAJ40A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMAJ40A requirements.
6.How does Aetrix verify that SMAJ40A is sourced from the original manufacturer or authorized distributors?
All SMAJ40A 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 SMAJ40A meets industry standards.
7.What is the process for return or replacement of SMAJ40A?
All SMAJ40A units undergo pre-shipment inspection (PSI). If there is an issue with SMAJ40A, 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 SMAJ40A part is unused and in its original packaging.
Return procedure for SMAJ40A:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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