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Taiwan Semiconductor Corporation SMAJ18AH
- Part No.:
- SMAJ18AH
- Manufacturer:
- Taiwan Semiconductor Corporation
- Category:
- TVS Diodes
- Package:
- DO-214AC, SMA
- Datasheet:
-
SMAJ18AH.pdf
- Description:
- TVS DIODE 18VWM 29.2VC DO214AC
- Quantity:
- Payment:
- Shipping:
Inventory:3,173
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Product details
Overview
SMAJ18AH 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 18 V working stand-off voltage (VWM), 20.0–22.1 V breakdown voltage (VBR), 29.2 V clamping voltage (VC) at 13.7 A peak pulse current, and 400 W peak pulse power (10/1000 µs). It is AEC-Q101 qualified and used in automotive on-board DC/DC converters.
For engineers reviewing the SMAJ18AH datasheet, SMAJ18AH pinout, SMAJ18AH application, or SMAJ18AH equivalent, key selection criteria include clamping performance under ISO 7637-2 Pulse 1/2a/2b/3a/3b, unidirectional polarity marking, moisture sensitivity level 1 compliance, and compatibility with automated SMT placement in high-reliability power supply designs.
Technical Context
The SMAJ18AH operates as a unidirectional avalanche diode, leveraging glass-passivated junction technology for stable breakdown behavior and low leakage (<1 µA at 18 V). Its fast response time (<1.0 ps) ensures suppression of ESD and load-dump transients before sensitive downstream circuitry is affected.
It meets ISO 7637-2 test requirements for automotive electronics-including Pulse 1 (inductive load disconnect), Pulse 2a (sudden load removal), Pulse 2b (supply line inductance), and Pulses 3a/3b (switching noise)-and is rated for TJ = –55 °C to +150 °C operation with 1 W steady-state power dissipation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VWM | 18 V - Maximum continuous reverse operating voltage before conduction begins |
| VBR min/max | 20.0 / 22.1 V @ 1 mA - Confirmed breakdown range ensuring reliable turn-on margin above VWM |
| VC @ IPPM | 29.2 V @ 13.7 A - Clamping voltage during 10/1000 µs surge, limiting stress on protected ICs |
| PPPM | 400 W (10/1000 µs) - Peak surge energy handling capacity for automotive load-dump events |
| IR @ VWM | <1 µA - Negligible leakage current preserving efficiency in always-on 12 V systems |
| Package | DO-214AC (SMA) - Standardized surface-mount outline compatible with IPC-7351B land patterns |
| AEC-Q101 | Qualified - Validated for automotive-grade reliability including temperature cycling, HTRB, and ESD |
Pinout & Package
DO-214AC (SMA) package: molded plastic case with matte tin-plated leads, cathode band marking polarity, 0.060 g weight, UL 94V-0 rated compound, JESD201 Class 2 whisker resistance, and J-STD-020 Level 1 moisture sensitivity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Low-side reference terminal | Connected to ground or low-impedance return path; defines conduction direction in unidirectional mode |
| Cathode | High-side surge input terminal | Connected to protected line (e.g., 12 V rail); clamps transients toward anode when voltage exceeds VBR |
Key Features
| Feature | Design Value |
|---|---|
| AEC-Q101 qualification | Validated for automotive under-hood environments including thermal cycling, humidity bias, and mechanical shock |
| Glass-passivated junction | Enhances long-term stability of VBR and reduces parameter drift across temperature and life cycles |
| Clamping ratio VC/VBR | 1.32 (29.2 V / 22.1 V max) - Tight ratio enables predictable voltage limiting without excessive headroom |
| ISO 7637-2 compliance | Passes Pulse 1 (–150 V/2 Ω), Pulse 2a (+100 V), Pulse 2b (+50 V), and Pulses 3a/3b (±200 V) waveforms |
| Fast response time | <1.0 ps - Enables suppression of sub-nanosecond ESD events before propagation into system ICs |
Applications
| Automotive On-Board DC/DC Converter | Industrial SMPS Input Stage |
|---|---|
Use Scenario: Protects primary-side controller ICs and gate drivers in 12 V-to-5 V/3.3 V buck converters subjected to battery load-dump transients. IC Role / Device Role: Unidirectional TVS placed between input rail and ground, clamping surges to ≤29.2 V during ISO 7637-2 Pulse 5a events. Use Value: Prevents latch-up or permanent damage to PWM controllers (e.g., MP2451, LM5007) by limiting transient overvoltage below their absolute maximum ratings. | Use Scenario: Shields AC-DC adapter output rails against coupling-induced spikes and switching noise in factory automation equipment. IC Role / Device Role: Standoff-rated TVS on secondary-side 24 V output, absorbing repetitive 10/1000 µs surges up to 400 W without degradation. Use Value: Maintains regulated output integrity during line disturbances, eliminating need for oversized output capacitors or redundant regulation stages. |
| LED Driver Power Input | Automotive Body Control Module (BCM) |
Use Scenario: Safeguards constant-current LED driver ICs (e.g., AL8860, LT3474) from ignition-switching transients in vehicle lighting systems. IC Role / Device Role: Unidirectional clamp on 12 V input rail upstream of buck converter stage; cathode tied to rail, anode to chassis ground. Use Value: Ensures uninterrupted illumination during cold-cranking (–4 V) and load-dump (+35 V) per ISO 16750-2, avoiding visible flicker or dropout. | Use Scenario: Protects microcontroller I/O and CAN transceiver power pins in BCMs exposed to alternator ripple and relay coil flyback. IC Role / Device Role: Localized TVS on 5 V/3.3 V internal supply rails, placed adjacent to MCU power entry points. Use Value: Reduces susceptibility to single-event functional interruptions caused by coupled transients, supporting ASIL-B system integrity. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMAJ18A | Same VWM (18 V), but lower VBR min (18.9 V) and higher VC (30.5 V); non-AEC-Q101 rated | Lacks automotive qualification; suitable only for commercial-grade industrial adapters or lighting | Select SMAJ18A only if AEC-Q101 is not required and clamping margin allows 30.5 V peak |
| SMBJ18AH | Same electrical specs but DO-214AA (SMB) package - 2.5 mm wider body, higher thermal mass, 600 W PPPM rating | Requires PCB footprint change; preferred where higher surge endurance or thermal derating margin is needed | Choose SMBJ18AH when system-level testing shows repeated 400 W surges cause thermal stress in SMA package |
Compared with SMAJ18A and SMBJ18AH, the SMAJ18AH uniquely balances AEC-Q101 compliance, DO-214AC footprint compatibility, and verified ISO 7637-2 Pulse 5a performance-making it optimal for space-constrained automotive modules where qualification and standardization are mandatory.
Availability
SMAJ18AH is available at Aetrix Electronics and suitable for automotive body control modules, industrial SMPS designs, and LED driver power inputs requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for SMAJ18AH 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 was developed specifically for automotive and industrial transient suppression, emphasizing AEC-Q101 reliability, standardized DO-214AC packaging, and full ISO 7637-2 waveform compliance across the 5 V–188 V range.
FAQ
What is the clamping voltage of SMAJ18AH under a 10/1000 µs surge?
The SMAJ18AH has a maximum clamping voltage (VC) of 29.2 V when subjected to its rated peak pulse current of 13.7 A using the standard 10/1000 µs waveform. This value is measured per Figure 5 in the official Taiwan Semiconductor datasheet (Version A2102) and ensures protected circuits remain below critical overvoltage thresholds during automotive load-dump events.
Is SMAJ18AH bidirectional or unidirectional?
SMAJ18AH is a unidirectional TVS diode, indicated by the absence of "C" or "CA" suffix and confirmed by its single cathode band marking and specification table listing only one polarity. It conducts only when the cathode is positive relative to the anode, making it appropriate for DC rail protection where reverse voltage is not expected.
Does SMAJ18AH meet AEC-Q101 reliability standards?
Yes, SMAJ18AH is explicitly AEC-Q101 qualified per the Taiwan Semiconductor datasheet (Version A2102, Page 1). This includes stress testing for temperature cycling, high-temperature reverse bias (HTRB), highly accelerated stress test (HAST), and ESD (HBM ≥8 kV, CDM ≥1 kV), validating its suitability for automotive under-hood and chassis applications.
What is the maximum operating junction temperature for SMAJ18AH?
The SMAJ18AH has a maximum operating junction temperature (TJ MAX) of +150 °C, as specified in the Absolute Maximum Ratings table. This rating supports use in engine compartment environments and high-power-density industrial converters where ambient temperatures exceed 105 °C, provided PCB thermal design maintains junction-to-ambient thermal resistance within limits.
How does SMAJ18AH differ from SMAJ18H?
SMAJ18AH offers tighter parameter tolerances than SMAJ18H: its VBR range is 20.0–22.1 V (vs. 20.0–24.4 V), and its clamping voltage is lower at 29.2 V (vs. 32.2 V) for the same 13.7 A surge. These improvements reduce voltage overshoot during transients and improve compatibility with low-voltage logic interfaces downstream of the protected rail.
SMAJ18AH 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:
- -
- Capacitance @ Frequency:
- -
- Operating Temperature:
- -55°C ~ 150°C (TJ)
- Grade:
- Automotive
- Qualification:
- AEC-Q101
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- DO-214AC (SMA)
SMAJ18AH FAQ
1.How can I place an order for SMAJ18AH through Aetrix?
Please submit a Request for Quotation (RFQ) for SMAJ18AH 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 SMAJ18AH reliable?
The price and inventory of SMAJ18AH are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMAJ18AH is usually 5 days.
3.What payment methods are accepted for SMAJ18AH?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMAJ18AH transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMAJ18AH?
SMAJ18AH orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMAJ18AH 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 SMAJ18AH?
For technical support, including SMAJ18AH datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMAJ18AH requirements.
6.How does Aetrix verify that SMAJ18AH is sourced from the original manufacturer or authorized distributors?
All SMAJ18AH 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 SMAJ18AH meets industry standards.
7.What is the process for return or replacement of SMAJ18AH?
All SMAJ18AH units undergo pre-shipment inspection (PSI). If there is an issue with SMAJ18AH, 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 SMAJ18AH part is unused and in its original packaging.
Return procedure for SMAJ18AH:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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