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Taiwan Semiconductor Corporation SMAJ18H
- Part No.:
- SMAJ18H
- Manufacturer:
- Taiwan Semiconductor Corporation
- Category:
- TVS Diodes
- Package:
- DO-214AC, SMA
- Datasheet:
-
SMAJ18H.pdf
- Description:
- TVS DIODE 18VWM 32.2VC DO214AC
- Quantity:
- Payment:
- Shipping:
Inventory:3,427
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Product details
Overview
SMAJ18H from Taiwan Semiconductor is a unidirectional 400W surface-mount transient voltage suppressor (TVS) diode in DO-214AC (SMA) package, with 20.0–24.4 V breakdown voltage (VBR), 18 V working stand-off voltage (VWM), and 32.2 V clamping voltage (VC) at 12.4 A peak pulse current. It delivers fast <1.0 ps response time and <1 µA reverse leakage above 10 V, designed for automotive-grade DC/DC converter protection per ISO 7637-2 Pulse 1/2a/2b/3a/3b.
For engineers reviewing the SMAJ18H datasheet, SMAJ18H pinout, SMAJ18H application, or SMAJ18H equivalent, this page provides verified electrical parameters, AEC-Q101 qualification status, clamping performance under 10/1000 µs surge, moisture sensitivity level (MSL 1), and direct alternatives for overvoltage protection in SMPS, lighting, and on-board power systems.
Technical Context
The SMAJ18H operates as a unidirectional avalanche diode with glass-passivated junction, optimized for single-pulse transient suppression in automotive and industrial power rails. Its 150 °C maximum junction temperature and -55 to +150 °C operating range support under-hood and high-temperature PCB environments.
It meets ISO 7637-2 Pulse 1 (inductive load dump), Pulse 2a/2b (switching transients), and Pulse 3a/3b (capacitive coupling noise), with 400 W peak pulse power (10/1000 µs) derated linearly above 25 °C ambient per Fig.2. Bidirectional variants use CH/CAH suffixes; SMAJ18H is unidirectional only.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VWM | 18 V - Maximum continuous reverse operating voltage before significant leakage; sets upper limit for protected circuit's nominal rail. |
| VBR @ IT=1 mA | 20.0–24.4 V - Breakdown threshold at test current; ensures reliable triggering during transients without false clamping. |
| VC @ IPPM=12.4 A | 32.2 V - Clamped voltage during 10/1000 µs surge; defines worst-case overvoltage seen by downstream ICs. |
| PPPM | 400 W - Peak pulse power handling (10/1000 µs); supports robust protection against ISO 7637-2-compliant surges. |
| IR @ VWM | <1 µA - Reverse leakage at 18 V; minimizes standby power loss and avoids false triggering in low-power systems. |
| TJMAX | 150 °C - Maximum junction temperature; enables operation in engine control units and high-ambient industrial enclosures. |
| Package | DO-214AC (SMA) - Standardized surface-mount outline with cathode band marking; compatible with automated pick-and-place. |
Pinout & Package
DO-214AC (SMA) package: molded epoxy case with matte tin-plated leads, polarity indicated by cathode band. Weight ≈ 0.060 g. Meets UL 94V-0 flammability and JESD201 Class 2 whisker resistance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Low-side reference terminal | Connected to ground or low-voltage return path; forms current path during reverse-biased clamping event. |
| Cathode | High-side surge input terminal | Connected to protected line (e.g., 12 V rail); avalanche conduction occurs when voltage exceeds VBR. |
Key Features
| Feature | Design Value |
|---|---|
| AEC-Q101 qualified | Validated for automotive electronics per stress test requirements including HTOL, TC, UHAST, and ESD-HBM/MM. |
| Glass passivated junction | Enhances long-term reliability and stability of VBR under thermal cycling and humidity exposure. |
| <1.0 ps response time | Enables clamping before sensitive logic or analog circuits experience damaging overvoltage edge rates. |
| ISO 7637-2 compliance | Guarantees survivability against standardized automotive transients (Pulse 1/2a/2b/3a/3b) without failure. |
| MSL Level 1 (J-STD-020) | Allows unlimited floor life and reflow soldering without baking; simplifies SMT manufacturing flow. |
Applications
| Automotive On-Board DC/DC Converter | Industrial Switching Mode Power Supply (SMPS) |
|---|---|
|
Use Scenario: Protects 12 V input stage of buck converter supplying microcontrollers in ADAS ECUs exposed to load-dump transients. IC Role / Device Role / Timing Role: Unidirectional TVS placed between input rail and ground to clamp ISO 7637-2 Pulse 1 (−120 V, 50 ms) to ≤32.2 V. Use Value: Prevents latch-up or gate oxide damage in synchronous MOSFET drivers by limiting overvoltage to safe margin below their absolute max rating. |
Use Scenario: Shields primary-side controller ICs in 48 V telecom SMPS during turn-on surge and line transients. IC Role / Device Role / Timing Role: Standoff-rated TVS across bulk capacitor input to absorb 400 W 10/1000 µs pulses without degradation. Use Value: Maintains system uptime by avoiding controller reset or MOSFET avalanche failure during repetitive switching-induced spikes. |
| LED Driver Lighting Module | Automotive Body Control Module (BCM) Power Input |
|
Use Scenario: Safeguards constant-current LED driver ICs in exterior lighting against ESD and cable discharge events. IC Role / Device Role / Timing Role: Fast-response TVS on 24 V supply rail to suppress sub-nanosecond ESD transients per IEC 61000-4-2. Use Value: Eliminates need for secondary filtering stages by clamping transients within 1.0 ps, preserving driver signal integrity. |
Use Scenario: Secures 12 V power entry point of BCM against battery reversal, jump-start surges, and alternator ripple. IC Role / Device Role / Timing Role: Primary overvoltage protector rated for ISO 7637-2 Pulse 2b (inductive switch-off) and Pulse 3b (capacitive coupling). Use Value: Enables single-device protection architecture instead of multi-stage TVS+varistor, reducing BOM count and board area. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient voltage suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMAJ18AH | Lower VBR range (20.0–22.1 V) and lower VC (29.2 V at 13.7 A); same package and power rating. | Better suited for tighter clamping margin where protected ICs have lower absolute max voltage rating. | Select SMAJ18AH if downstream ICs require clamping below 30 V; otherwise SMAJ18H offers higher VBR tolerance for noisy rails. |
| SMBJ18H | Same VWM/VBR/VC specs but in larger DO-214AA (SMB) package; 600 W PPPM (10/1000 µs). | Higher surge capacity suits applications with infrequent but extreme transients (e.g., heavy-duty vehicle alternators). | Choose SMBJ18H only if 600 W rating is required and PCB layout allows larger footprint; SMAJ18H is optimal for space-constrained automotive modules. |
Compared with SMAJ18AH and SMBJ18H, the SMAJ18H balances clamping precision, compact DO-214AC footprint, and AEC-Q101 qualification-making it the preferred choice for volume automotive DC/DC converters where board space and qualification compliance are critical.
Availability
SMAJ18H is available at Aetrix Electronics and suitable for automotive on-board DC/DC converters, industrial switching mode power supplies, and LED driver lighting modules requiring stable component supply with full AEC-Q101 traceability and MSL Level 1 handling.
Supply support for SMAJ18H 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 Taiwanese semiconductor manufacturer specializing in discrete power devices, TVS diodes, rectifiers, and MOSFETs for automotive, industrial, and consumer markets.
The SMAJ series was developed specifically for AEC-Q101-compliant transient protection in automotive power electronics, emphasizing fast response, stable clamping, and high-reliability packaging for under-hood deployment.
FAQ
What is the clamping voltage of SMAJ18H at its rated peak pulse current?
The SMAJ18H has a maximum clamping voltage (VC) of 32.2 V when subjected to its rated peak pulse current of 12.4 A under the standard 10/1000 µs waveform. This value is measured per JEDEC test conditions and guarantees that downstream components see no more than 32.2 V during surge events, provided layout minimizes parasitic inductance. The SMAJ18H maintains this clamping performance across its full operating temperature range.
Is SMAJ18H suitable for bidirectional transient protection?
No, SMAJ18H is a unidirectional TVS diode intended for protection of positive-polarity DC lines only. For bidirectional applications such as AC lines or differential data buses, TSC offers SMAJ18CH (with CH suffix) - a bidirectional variant with symmetrical breakdown in both directions. Using SMAJ18H in reverse-biased configuration beyond its specified VWM risks permanent damage due to lack of reverse avalanche capability.
Does SMAJ18H meet automotive qualification standards?
Yes, SMAJ18H is AEC-Q101 qualified and explicitly tested to meet ISO 7637-2 Pulse 1, 2a, 2b, 3a, and 3b transient immunity requirements. Its glass-passivated junction, MSL Level 1 rating, and 150 °C TJMAX further validate its suitability for automotive power electronics, including engine control units and body control modules.
What is the reverse leakage current specification for SMAJ18H at its working voltage?
At its working stand-off voltage (VWM) of 18 V, the SMAJ18H exhibits a maximum reverse leakage current (IR) of 1 µA at 25 °C. This ultra-low leakage ensures minimal power loss in always-on automotive modules and prevents false triggering in high-impedance sensing circuits. Leakage remains below 5 µA up to 125 °C per thermal derating curves.
How does SMAJ18H differ from SMAJ18AH in practical design use?
SMAJ18AH features a narrower breakdown voltage range (20.0–22.1 V vs. 20.0–24.4 V for SMAJ18H) and lower clamping voltage (29.2 V vs. 32.2 V). In practice, SMAJ18AH provides tighter voltage control for systems with strict overvoltage margins, while SMAJ18H offers greater tolerance for rail variation and noise. Both share identical DO-214AC packaging, AEC-Q101 qualification, and 400 W surge rating.
SMAJ18H 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:
- 32.2V
- Current - Peak Pulse (10/1000µs):
- 12.4A
- 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)
SMAJ18H FAQ
1.How can I place an order for SMAJ18H through Aetrix?
Please submit a Request for Quotation (RFQ) for SMAJ18H 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 SMAJ18H reliable?
The price and inventory of SMAJ18H are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMAJ18H is usually 5 days.
3.What payment methods are accepted for SMAJ18H?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMAJ18H transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMAJ18H?
SMAJ18H orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMAJ18H 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 SMAJ18H?
For technical support, including SMAJ18H datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMAJ18H requirements.
6.How does Aetrix verify that SMAJ18H is sourced from the original manufacturer or authorized distributors?
All SMAJ18H 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 SMAJ18H meets industry standards.
7.What is the process for return or replacement of SMAJ18H?
All SMAJ18H units undergo pre-shipment inspection (PSI). If there is an issue with SMAJ18H, 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 SMAJ18H part is unused and in its original packaging.
Return procedure for SMAJ18H:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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