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Taiwan Semiconductor Corporation SMAJ18A
- Part No.:
- SMAJ18A
- Manufacturer:
- Taiwan Semiconductor Corporation
- Category:
- TVS Diodes
- Package:
- DO-214AC, SMA
- Datasheet:
-
SMAJ18A.pdf
- Description:
- TVS DIODE 18VWM 29.2VC DO214AC
- Quantity:
- Payment:
- Shipping:
Inventory:5,676
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Product details
Overview
SMAJ18A from Taiwan Semiconductor is a unidirectional surface-mount transient voltage suppressor (TVS) diode in DO-214AC (SMA) package, designed for clamping fast transients in DC power lines and signal paths. It features a 18 V working stand-off voltage (VWM), 20.0–22.1 V breakdown voltage (VBR) at 1 mA test current, 29.2 V maximum clamping voltage (VC) at 13.7 A peak pulse current, and 400 W peak pulse power rating with 10/1000 µs waveform.
For engineers reviewing the SMAJ18A datasheet, SMAJ18A pinout, SMAJ18A application, or SMAJ18A equivalent, key selection criteria include clamping performance under ISO 7637-2 Pulse 1/2a/2b/3a/3b, low leakage (<1 µA @ 18 V), fast response (<1.0 ps), and compatibility with automated SMT placement in industrial power supplies and DC/DC converters.
Technical Context
The SMAJ18A operates as a unidirectional avalanche diode, leveraging glass-passivated junction technology to achieve stable breakdown and low capacitance. Its clamping behavior is defined by a sharp knee in the I-V curve above VBR, with guaranteed VC ≤ 29.2 V at IPPM = 13.7 A under standardized 10/1000 µs surge conditions.
Thermal derating begins above TA = 25°C per Fig.2, and it supports continuous operation from –55°C to +150°C junction temperature. The device meets JESD201 Class 2 whisker resistance and UL 94V-0 flammability requirements, with matte tin-plated leads compliant to J-STD-002 solderability standards.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VWM | 18 V - Maximum continuous reverse operating voltage before significant leakage; defines safe DC bias margin in protected circuits. |
| VBR min/max | 20.0 / 22.1 V @ 1 mA - Confirmed avalanche onset range; ensures predictable turn-on during overvoltage events. |
| VC @ IPPM | 29.2 V @ 13.7 A - Clamped voltage seen by downstream circuitry during 10/1000 µs surge; limits stress on ICs and MOSFETs. |
| PPPM | 400 W - Peak surge energy handling capability; sufficient for automotive load-dump and inductive switching transients. |
| IR @ VWM | <1 µA - Negligible standby leakage at rated stand-off; avoids power loss in battery-backed or low-quiescent systems. |
| Response time | <1.0 ps - Sub-nanosecond junction response enables protection of high-speed interfaces and sensitive analog inputs. |
| Package | DO-214AC (SMA) - Industry-standard surface-mount outline; compatible with standard reflow profiles and pick-and-place equipment. |
Pinout & Package
DO-214AC (SMA) package: molded epoxy case with cathode band marking; single-anode/cathode configuration; polarity indicated by molded band on cathode end; weight ≈ 0.060 g.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Current entry terminal during forward conduction | Connected to lower-potential side (e.g., GND or return path); defines directionality in unidirectional TVS operation. |
| Cathode | Current exit terminal during forward conduction; clamping node during reverse surge | Connected to protected line (e.g., 12 V rail); conducts avalanche current to ground when VLINE exceeds VBR. |
Key Features
| Feature | Design Value |
|---|---|
| Glass-passivated junction | Ensures stable, repeatable breakdown voltage and long-term reliability under thermal cycling and humidity exposure. |
| ISO 7637-2 compliance (Pulse 1/2a/2b/3a/3b) | Validated for automotive ECU-level transient immunity without external filtering; reduces need for additional protection stages. |
| Moisture sensitivity level 1 (J-STD-020) | Eliminates bake-out requirement prior to reflow; supports standard SMT assembly flow without special handling. |
| Halogen-free & RoHS-compliant | Meets IEC 61249-2-21 and EU RoHS Directive; suitable for environmentally regulated industrial and automotive programs. |
| Fast response & low clamping | Sub-1 ps turn-on and 29.2 V clamping at 13.7 A enable protection of 3.3 V/5 V logic rails and gate drivers without overvoltage damage. |
Applications
| Automotive Body Control Module (BCM) | Industrial SMPS Input Stage |
|---|---|
Use Scenario: Protects microcontroller I/O and CAN transceiver power rails against load dump and jump-start transients per ISO 7637-2. IC Role / Device Role / Timing Role: Unidirectional clamping diode placed between 12 V supply and local ground plane. Use Value: Limits voltage excursion to ≤29.2 V during 400 W surges, preventing latch-up or oxide breakdown in 3.3 V domain ICs. |
Use Scenario: Shields primary-side controller ICs and gate drivers in offline AC/DC adapters against line-induced surges. IC Role / Device Role / Timing Role: Standoff-clamp element across bulk capacitor input, triggered only during >20 V excursions. Use Value: Maintains <1 µA leakage at 18 V nominal, avoiding efficiency loss while delivering sub-ns response to 10/1000 µs spikes. |
| LED Driver DC Bus Protection | On-board DC/DC Converter Input |
Use Scenario: Safeguards constant-current LED driver ICs from inductive kickback when driving high-power arrays. IC Role / Device Role / Timing Role: Parallel-connected transient clamp on 24 V or 48 V DC bus feeding buck/boost controllers. Use Value: Withstands 13.7 A peak impulse without degradation, enabling robust operation in outdoor lighting with frequent switching cycles. |
Use Scenario: Guards point-of-load (POL) DC/DC converters in telecom and computing systems against board-level ESD and coupling noise. IC Role / Device Role / Timing Role: Localized TVS at converter input capacitor, minimizing trace inductance in clamping path. Use Value: DO-214AC footprint allows compact layout; 29.2 V clamping ensures secondary-side LDOs and FPGAs remain within absolute max ratings. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMBJ18A (Bourns) | Same VWM (18 V), but higher VC = 28.8 V @ 14.3 A; SMB package (DO-214AA) has larger footprint and 10% higher thermal mass. | Preferred where board space permits larger package and slightly tighter clamping is required. | Select SMBJ18A if PCB layout allows DO-214AA and lower clamping voltage is critical; verify pad layout compatibility. |
| P6SMB18A (Littelfuse) | Identical VWM (18 V), VC = 29.2 V @ 13.7 A, same DO-214AC package; differs in moisture sensitivity (MSL 2 vs MSL 1) and RoHS/halogen status (halogen-free not explicitly stated). | Suitable for non-automotive industrial use where MSL 1 is not mandated and halogen-free is optional. | Choose P6SMB18A for cost-sensitive industrial designs where MSL 1 and halogen-free compliance are not required. |
Compared with SMBJ18A and P6SMB18A, the SMAJ18A offers MSL 1 handling, halogen-free construction, and identical clamping performance in the smallest DO-214AC footprint-making it optimal for space-constrained, automotive-qualified, and green-design applications.
Availability
SMAJ18A is available at Aetrix Electronics and suitable for automotive body electronics, industrial switch-mode power supplies, LED driver systems, and on-board DC/DC converter designs requiring stable component supply and full ISO 7637-2 compliance.
Supply support for SMAJ18A 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 industrial, automotive, and consumer markets.
The SMAJ series was developed specifically for high-reliability, surface-mount transient suppression in harsh environments-emphasizing low clamping, fast response, and automotive-grade qualification including ISO 7637-2 and JESD201 whisker resistance.
FAQ
What is the maximum clamping voltage of the SMAJ18A under standard surge conditions?
The SMAJ18A exhibits a maximum clamping voltage (VC) of 29.2 V when subjected to a 10/1000 µs waveform with a peak pulse current (IPPM) of 13.7 A. This value is measured per JEDEC standards and guarantees that downstream components experience no more than 29.2 V during such transients. The SMAJ18A maintains this clamping performance consistently across its qualified operating temperature range of –55°C to +150°C.
Is the SMAJ18A suitable for bidirectional transient protection?
No, the SMAJ18A is a unidirectional TVS diode, intended for protection of DC power rails with defined polarity. For bidirectional applications-such as AC lines or data buses requiring symmetrical clamping-Taiwan Semiconductor specifies the SMAJ18CA variant (with "CA" suffix). The SMAJ18A's cathode band marking and electrical characteristics apply only in the reverse direction; forward conduction follows standard diode behavior with VF ≈ 3.5 V at 25 A.
Does the SMAJ18A require special handling during PCB assembly?
No, the SMAJ18A is rated MSL 1 per J-STD-020, meaning it can be stored indefinitely at ambient conditions and placed directly into standard reflow profiles without baking or dry-pack requirements. Its matte tin-plated leads meet J-STD-002 solderability specifications, and the DO-214AC package is fully compatible with automated pick-and-place and reflow soldering processes used in high-volume manufacturing.
How does the SMAJ18A compare to the SMAJ18 (non-A) version?
The SMAJ18A offers tighter breakdown voltage tolerance (20.0–22.1 V) compared to the SMAJ18 (20.0–24.4 V), resulting in more consistent clamping onset and reduced variation in protected circuit margin. Both share identical VWM (18 V), VC (29.2 V), and PPPM (400 W), but the "A" suffix denotes enhanced VBR uniformity-critical for designs requiring precise overvoltage threshold control and minimal unit-to-unit dispersion.
Can the SMAJ18A be used in automotive applications requiring ISO 7637-2 compliance?
Yes, the SMAJ18A is explicitly validated to meet ISO 7637-2 Pulse 1, 2a, 2b, 3a, and 3b test requirements-covering common automotive transient threats including battery disconnection, relay switching, and capacitive coupling. Its glass-passivated junction, MSL 1 rating, and –55°C to +150°C operating range make it suitable for under-hood and cabin ECUs where environmental robustness is mandatory. The SMAJ18A datasheet confirms full compliance without derating or external circuit modifications.
SMAJ18A 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):
- 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)
SMAJ18A FAQ
1.How can I place an order for SMAJ18A through Aetrix?
Please submit a Request for Quotation (RFQ) for SMAJ18A 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 SMAJ18A reliable?
The price and inventory of SMAJ18A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMAJ18A is usually 5 days.
3.What payment methods are accepted for SMAJ18A?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMAJ18A transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMAJ18A?
SMAJ18A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMAJ18A 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 SMAJ18A?
For technical support, including SMAJ18A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMAJ18A requirements.
6.How does Aetrix verify that SMAJ18A is sourced from the original manufacturer or authorized distributors?
All SMAJ18A 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 SMAJ18A meets industry standards.
7.What is the process for return or replacement of SMAJ18A?
All SMAJ18A units undergo pre-shipment inspection (PSI). If there is an issue with SMAJ18A, 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 SMAJ18A part is unused and in its original packaging.
Return procedure for SMAJ18A:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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