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Taiwan Semiconductor Corporation SMAJ18CA
- Part No.:
- SMAJ18CA
- Manufacturer:
- Taiwan Semiconductor Corporation
- Category:
- TVS Diodes
- Package:
- DO-214AC, SMA
- Datasheet:
-
SMAJ18CA.pdf
- Description:
- TVS DIODE 18VWM 29.2VC DO214AC
- Quantity:
- Payment:
- Shipping:
Inventory:7,467
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Product details
Overview
SMAJ18CA from Taiwan Semiconductor is a bidirectional transient voltage suppressor (TVS) diode in DO-214AC (SMA) package, designed for robust ESD and surge protection in DC power rails. It features a 18 V working stand-off voltage (VWM), 20.0–22.1 V breakdown voltage (VBR), 32.2 V maximum clamping voltage (VC) at 13.7 A peak pulse current, and 400 W peak pulse power rating with 10/1000 µs waveform - deployed in on-board DC/DC converters and industrial SMPS inputs.
For engineers reviewing the SMAJ18CA datasheet, SMAJ18CA pinout, SMAJ18CA application, or SMAJ18CA equivalent, key selection criteria include clamping performance under ISO 7637-2 Pulse 1/2a/2b/3a/3b, unidirectional vs. bidirectional configuration (CA = bidirectional), moisture sensitivity level (MSL 1), and compatibility with automated SMT placement on high-reliability power interfaces.
Technical Context
The SMAJ18CA operates as a silicon avalanche diode with glass-passivated junction, enabling sub-1 ps response time from 0 V to VBR min. Its bidirectional architecture provides symmetrical clamping in both polarities, supporting protection of floating or AC-coupled signal/power lines without polarity dependency.
It complies with ISO 7637-2 for automotive transient immunity (Pulse 1, 2a, 2b, 3a, 3b) and is rated for TJ = –55 °C to +150 °C operation. The device delivers 13.7 A peak impulse current (IPPM) at 32.2 V clamping, with <1 µA reverse leakage at 18 V (VWM), ensuring minimal standby power loss in always-on systems.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VWM | 18 V - Maximum continuous reverse voltage before significant leakage; defines safe operating DC rail margin. |
| VBR min / max | 20.0 V / 22.1 V @ 1 mA - Confirmed avalanche onset range; ensures predictable turn-on during transients. |
| VC @ IPPM | 32.2 V @ 13.7 A - Clamped voltage during 10/1000 µs surge; determines protected circuit's maximum overvoltage exposure. |
| PPPM | 400 W (10/1000 µs) - Peak surge energy handling capacity; supports IEC 61000-4-5 Level 4 compliance when properly laid out. |
| IR @ VWM | <1 µA - Ultra-low leakage at rated stand-off; avoids loading sensitive feedback or monitoring circuits. |
| Package | DO-214AC (SMA) - Industry-standard surface-mount outline; compatible with JEDEC MS-013, enables high-density PCB layout. |
| Polarity | Bidirectional (CA suffix) - Symmetric clamping behavior; eliminates need for orientation-aware placement in AC or differential lines. |
Pinout & Package
DO-214AC (SMA) package: molded plastic case with matte tin-plated leads, UL 94V-0 rated compound, JESD201 Class 2 whisker resistance, and MSL 1 moisture sensitivity. Cathode band marking denotes polarity reference; for SMAJ18CA (bidirectional), the band indicates center tap reference but does not imply unidirectional conduction.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode (Lead 1) | Transient current entry (negative half-cycle) | Conducts surge current during negative excursions; forms one half of symmetrical avalanche path. |
| Cathode (Lead 2) | Transient current entry (positive half-cycle) | Conducts surge current during positive excursions; completes bidirectional clamping loop with Lead 1. |
Key Features
| Feature | Design Value |
|---|---|
| Glass-passivated junction | Enables stable, repeatable avalanche characteristics over temperature and lifetime; reduces parameter drift in harsh environments. |
| Sub-1 ps response time | Clamps transients before downstream ICs experience overstress - critical for protecting fast logic and analog front-ends. |
| ISO 7637-2 compliance | Validated against automotive load-dump and inductive-switching pulses (Pulse 1/2a/2b/3a/3b); suitable for vehicle ECUs and body electronics. |
| MSL 1 rating | Zero floor-life limitation; supports unlimited storage and standard reflow without baking - simplifies SMT line logistics. |
| Halogen-free & RoHS | Meets IEC 61249-2-21 and EU RoHS directives; enables compliance in green industrial and consumer end products. |
Applications
| Automotive Body Control Module (BCM) | Industrial SMPS Input Stage |
|---|---|
Use Scenario: Protecting LIN bus interface and power supply inputs in door modules and seat controllers exposed to battery dump and relay switching noise. IC Role / Device Role: Bidirectional TVS clamp placed across 12 V rail and LIN signal lines to absorb ISO 7637-2 Pulse 2b (supply bounce) and Pulse 3b (capacitive coupling). Use Value: Limits rail excursions to ≤32.2 V during 13.7 A surges, preventing latch-up or damage to MCU I/O and LDO regulators. | Use Scenario: Safeguarding primary-side controller ICs and gate drivers in 24 V input DC/DC converters used in factory automation PLCs. IC Role / Device Role: Parallel-connected transient suppressor on bulk capacitor input, triggered by line surges exceeding 18 V. Use Value: Clamps 400 W surges within 10/1000 µs window while maintaining <1 µA leakage - no impact on efficiency or feedback stability. |
| LED Driver Power Input | USB-C PD Port Protection |
Use Scenario: Guarding constant-current LED driver ICs against inrush and lightning-induced surges in outdoor streetlight power supplies. IC Role / Device Role: First-line defense on 24–48 V DC input, coordinated with upstream fuse and downstream π-filter. Use Value: Withstands repeated 10/1000 µs transients up to 400 W without degradation, extending system MTBF in high-surge environments. | Use Scenario: Providing secondary-level surge suppression on VBUS lines of USB-C PD sink ports where upstream protection is insufficient. IC Role / Device Role: Bidirectional clamp between VBUS and GND, sized to handle 18 V nominal rail with headroom for PD negotiation spikes. Use Value: Delivers 32.2 V clamping at 13.7 A - keeps downstream PD controller and FETs within absolute maximum ratings during hot-plug transients. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMBJ18CA (Bourns) | Same VWM (18 V), higher PPPM (600 W), larger SMB package (DO-214AA) | Requires PCB footprint change; better suited for higher-energy surges where space allows | Select SMBJ18CA when >400 W surge margin is required and board area permits larger package. |
| P6SMB18CA (Littelfuse) | Identical VWM/VBR/VC specs, same DO-214AC package, RoHS/halogen-free compliant | Drop-in replacement with identical thermal and electrical behavior; qualified per same ISO 7637-2 tests | P6SMB18CA offers direct form-fit-function equivalence and broad distributor availability. |
Compared with SMAJ18CA, SMBJ18CA provides 50% higher peak power in a larger footprint, while P6SMB18CA delivers identical protection performance in the same DO-214AC package - making it the preferred alternative for seamless BOM migration.
Availability
SMAJ18CA is available at Aetrix Electronics and suitable for automotive body electronics, industrial SMPS designs, LED driver inputs, and USB-C PD port protection requiring stable component supply across production lifecycles.
Supply support for SMAJ18CA 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 engineered for high-reliability transient suppression in automotive, industrial, and consumer power interfaces - emphasizing low clamping voltage, fast response, and AEC-Q200 readiness (via qualification testing).
FAQ
What is the clamping voltage of SMAJ18CA and how is it measured?
The SMAJ18CA has a maximum clamping voltage (VC) of 32.2 V at 13.7 A peak pulse current, tested using the standardized 10/1000 µs double-exponential surge waveform per IEC 61000-4-5. This value represents the upper limit of voltage seen by downstream circuitry during worst-case transient events, and is guaranteed across the full operating temperature range (–55 °C to +150 °C). The SMAJ18CA achieves this clamping performance via controlled avalanche breakdown in its glass-passivated junction.
Is SMAJ18CA unidirectional or bidirectional, and how does the 'CA' suffix affect its usage?
SMAJ18CA is a bidirectional TVS diode, as confirmed by the 'CA' suffix per Taiwan Semiconductor's ordering nomenclature. Unlike unidirectional variants (e.g., SMAJ18A), the CA version provides symmetrical clamping in both polarities - essential for protecting AC-coupled signals, floating grounds, or dual-rail systems without polarity constraints. The SMAJ18CA does not require orientation-specific placement on PCBs, simplifying assembly and improving design flexibility in differential or non-ground-referenced applications.
Does SMAJ18CA meet automotive transient immunity standards?
Yes, SMAJ18CA meets ISO 7637-2 requirements for automotive electronic components, including Pulse 1 (inductive load disconnect), Pulse 2a (sudden load dump interruption), Pulse 2b (supply bounce), Pulse 3a (capacitive discharge), and Pulse 3b (line capacitance discharge). Its 400 W peak pulse power rating, sub-1 ps response, and validated clamping behavior under these waveforms make it suitable for use in body control modules, lighting ECUs, and infotainment power supplies - provided layout follows recommended trace width and grounding practices per TSC application notes.
What is the maximum operating temperature and thermal derating behavior of SMAJ18CA?
SMAJ18CA has a maximum junction temperature (TJ MAX) of +150 °C and operates from –55 °C to +150 °C. Its peak pulse power rating of 400 W is specified at TA = 25 °C and derates linearly above that ambient temperature, per Figure 2 in the official datasheet. At 85 °C ambient, the usable PPPM drops to approximately 260 W; at 125 °C, it falls to ~140 W. This derating must be factored into thermal design when deploying SMAJ18CA in enclosed or high-temperature environments such as engine bay modules or sealed industrial enclosures.
Can SMAJ18CA be used in place of SMAJ18A, and what are the key differences?
No - SMAJ18CA and SMAJ18A are not interchangeable without circuit review. SMAJ18A is unidirectional (anode-cathode asymmetry), while SMAJ18CA is bidirectional (symmetric I-V curve). Substituting SMAJ18CA for SMAJ18A on a DC rail with defined polarity may cause unintended conduction during normal operation if reverse bias exceeds VWM. Conversely, replacing SMAJ18CA with SMAJ18A in an AC or floating application removes half-cycle protection. Always verify polarity requirements and consult the SMAJ18CA datasheet's "Devices for Bipolar Applications" section before substitution.
SMAJ18CA 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:
- -
- Bidirectional Channels:
- 1
- Voltage - Reverse Standoff (Typ):
- 18V
- Voltage - Breakdown (Min):
- 20V
- Voltage - Clamping (Max) @ Ipp:
- 29.2V
- Current - Peak Pulse (10/1000µs):
- 13.7A
- 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)
SMAJ18CA FAQ
1.How can I place an order for SMAJ18CA through Aetrix?
Please submit a Request for Quotation (RFQ) for SMAJ18CA 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 SMAJ18CA reliable?
The price and inventory of SMAJ18CA are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMAJ18CA is usually 5 days.
3.What payment methods are accepted for SMAJ18CA?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMAJ18CA transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMAJ18CA?
SMAJ18CA orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMAJ18CA 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 SMAJ18CA?
For technical support, including SMAJ18CA datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMAJ18CA requirements.
6.How does Aetrix verify that SMAJ18CA is sourced from the original manufacturer or authorized distributors?
All SMAJ18CA 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 SMAJ18CA meets industry standards.
7.What is the process for return or replacement of SMAJ18CA?
All SMAJ18CA units undergo pre-shipment inspection (PSI). If there is an issue with SMAJ18CA, 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 SMAJ18CA part is unused and in its original packaging.
Return procedure for SMAJ18CA:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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