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Taiwan Semiconductor Corporation SMA4S18AH
- Part No.:
- SMA4S18AH
- Manufacturer:
- Taiwan Semiconductor Corporation
- Category:
- TVS Diodes
- Package:
- SOD-128
- Datasheet:
-
SMA4S18AH.pdf
- Description:
- TVS DIODE 18VWM 29.2VC SOD128
- Quantity:
- Payment:
- Shipping:
Inventory:34,985
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Product details
Overview
SMA4S18AH from Taiwan Semiconductor is a unidirectional 400W surface-mount transient voltage suppressor (TVS) diode with a 18V working stand-off voltage, 20.1–22.2V breakdown voltage at 1mA, and 29.2V clamping voltage at 13.7A peak pulse current; used for overvoltage protection in BLDC motor drives and automotive battery management systems.
For engineers reviewing the SMA4S18AH datasheet, SMA4S18AH pinout, SMA4S18AH application, or SMA4S18AH equivalent, key selection criteria include its SOD-128 package, 175°C junction rating, AEC-Q101 qualification, unidirectional polarity, and verified 400W 10/1000μs surge capability under automotive-grade reliability requirements.
Technical Context
The SMA4S18AH operates as a unidirectional avalanche diode, leveraging glass-passivated junction technology to deliver precise voltage clamping during transient events. Its thermal design supports 175°C maximum junction temperature and achieves 20°C/W junction-to-lead resistance when mounted on a 5mm × 5mm copper pad PCB.
It complies with JESD201 Class 2 whisker resistance and J-STD-020 moisture sensitivity level 1, confirming suitability for reflow-soldered automotive and industrial assemblies. The device exhibits a low VBR temperature coefficient of 0.095%/°C, ensuring stable breakdown behavior across operating temperature ranges.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VWM | 18 V - Maximum continuous reverse operating voltage before conduction begins |
| VBR min/max | 20.1 V / 22.2 V - Breakdown voltage range at 1 mA test current; defines turn-on threshold consistency |
| VC @ IPPM | 29.2 V - Clamping voltage at 13.7 A peak pulse current; limits downstream voltage stress |
| PPPM | 400 W - Peak pulse power handling per 10/1000 μs waveform; meets IEC 61000-4-5 Level 4 |
| TJ max | +175 °C - Maximum junction temperature; enables operation in under-hood automotive environments |
| RθJL | 20 °C/W - Junction-to-lead thermal resistance; supports reliable heat transfer to PCB copper |
Pinout & Package
Package: SOD-128 - Surface-mount plastic package with cathode band marking, matte tin-plated leads, UL 94V-0 molding compound, and 0.028 g mass.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Current entry terminal in forward bias | Connected to lower-potential side of protected circuit; defines unidirectional conduction path |
| Cathode | Current exit terminal in forward bias; marked by band | Connected to higher-potential rail (e.g., VBUS); provides reverse-biased clamping to ground during transients |
Key Features
| Feature | Design Value |
|---|---|
| AEC-Q101 qualified | Validated for automotive applications including engine control units and body electronics |
| Glass-passivated junction | Ensures stable electrical parameters and long-term reliability under thermal cycling |
| VBR tempco: 0.095%/°C | Minimizes drift in clamping threshold across -55°C to +175°C operating range |
| Moisture sensitivity level 1 | Eliminates bake requirement prior to reflow soldering; reduces manufacturing overhead |
Applications
| BLDC Motor Drive Protection | Automotive Battery Management |
|---|---|
Use Scenario: Suppresses inductive kickback and load dump transients in 12–48V BLDC motor gate drivers and power stages. IC Role / Device Role / Timing Role: Unidirectional TVS diode placed across motor phase terminals or supply rails to clamp voltage spikes. Use Value: Limits transient voltage to ≤29.2V at 13.7A, protecting MOSFETs and gate drivers rated for 30–40V absolute maximum. | Use Scenario: Guards BMS front-end analog sensing circuits and MCU inputs against jump-start surges and alternator load dump. IC Role / Device Role / Timing Role: Standoff-rated protector on 18V-rated voltage monitoring lines and CAN bus power rails. Use Value: Maintains 18V working stand-off while clamping to 29.2V, preserving signal integrity without false triggering. |
| LED Driver Surge Suppression | Industrial SMPS Input Protection |
Use Scenario: Shields constant-current LED driver ICs and feedback resistors from line surges in outdoor lighting systems. IC Role / Device Role / Timing Role: Parallel-connected transient suppressor on DC input bus upstream of buck controller. Use Value: Absorbs 400W pulses without degradation, enabling compliance with IEC 61000-4-5 for streetlight installations. | Use Scenario: Protects primary-side rectifier and controller ICs in 24–48V industrial switch-mode power supplies. IC Role / Device Role / Timing Role: Input-stage TVS on bulk capacitor rail to limit surge-induced overvoltage. Use Value: Withstands repeated 10/1000μs transients up to 13.7A, extending capacitor and MOSFET lifetime. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMAJ18A | Lower PPPM (400W same), but higher VC = 32.4V at 12.3A; 150°C TJ max | Not AEC-Q101 qualified; limited to commercial/industrial use | Choose SMAJ18A only if automotive qualification is unnecessary and higher clamping voltage is acceptable |
| SMBJ18A | Same VWM/VBR specs, but SMB package (larger footprint); PPPM = 600W, VC = 29.2V at 20.5A | Higher surge margin but requires PCB area increase; not drop-in compatible | Select SMBJ18A when 600W surge headroom is required and SOD-128 board space is constrained |
Compared with SMAJ18A and SMBJ18A, the SMA4S18AH uniquely combines AEC-Q101 qualification, SOD-128 compactness, and 29.2V clamping at 13.7A-making it optimal for space-constrained automotive modules where reliability and thermal performance are critical.
Availability
SMA4S18AH is available at Aetrix Electronics and suitable for BLDC motor drives, automotive battery management systems, LED lighting surge protection, and industrial SMPS requiring stable component supply with full traceability and long-term lifecycle support.
Supply support for SMA4S18AH 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, and rectifiers with global distribution and AEC-Q101 validation capabilities.
The SMA4SxxAH series is designed specifically for high-reliability automotive and industrial transient suppression, emphasizing compact SOD-128 packaging, tight VBR tolerance, and robust thermal performance up to 175°C junction temperature.
FAQ
What is the clamping voltage of the SMA4S18AH and how is it measured?
The SMA4S18AH has a maximum clamping voltage (VC) of 29.2 V, measured at a peak pulse current (IPPM) of 13.7 A using a 10/1000 μs waveform. This value is specified in the Electrical Specifications table and reflects the voltage across the device during standardized surge testing. It ensures downstream components see no more than 29.2 V during transient events, making the SMA4S18AH suitable for protecting 30 V-rated ICs and MOSFETs.
Is the SMA4S18AH AEC-Q101 qualified and what does that mean for automotive use?
Yes, the SMA4S18AH is AEC-Q101 qualified, meaning it has passed stress tests for temperature cycling, humidity, mechanical shock, and high-temperature operating life required for automotive electronic components. This qualification confirms its suitability for under-hood and chassis-mounted applications such as BLDC motor controllers and battery management systems where reliability under harsh conditions is mandatory.
What is the thermal resistance from junction to lead (RθJL) for the SMA4S18AH?
The SMA4S18AH has a typical junction-to-lead thermal resistance (RθJL) of 20 °C/W when mounted on a 5 mm × 5 mm copper pad PCB. This parameter quantifies how effectively heat transfers from the silicon die to the PCB copper via the leads, directly influencing power derating and sustained surge capability-critical for designs operating near thermal limits.
Does the SMA4S18AH have unidirectional or bidirectional polarity, and how is it identified?
The SMA4S18AH is a unidirectional TVS diode, indicated by the cathode band marking on the SOD-128 package. In circuit layout, the banded end connects to the higher-potential rail (e.g., VBUS), while the anode connects toward ground or lower potential. This configuration enables clamping only during negative transients relative to the cathode, matching standard DC power rail protection needs.
What is the maximum steady-state power dissipation (PD) for the SMA4S18AH?
The SMA4S18AH has a steady-state power dissipation (PD) rating of 7.5 W at TL = 25°C, measured with the device mounted on a 5 mm × 5 mm copper pad test board. This value applies to continuous DC or low-frequency leakage conditions-not transient events-and must be derated linearly above 25°C ambient per the published derating curve in the datasheet.
SMA4S18AH Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Taiwan Semiconductor Corporation
- Package/Case:
- SOD-128
- Series:
- -
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Type:
- Zener
- Unidirectional Channels:
- 1
- Bidirectional Channels:
- -
- Voltage - Reverse Standoff (Typ):
- 18V
- Voltage - Breakdown (Min):
- 20.1V
- 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 ~ 175°C (TJ)
- Grade:
- Automotive
- Qualification:
- AEC-Q101
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SOD-128
SMA4S18AH FAQ
1.How can I place an order for SMA4S18AH through Aetrix?
Please submit a Request for Quotation (RFQ) for SMA4S18AH 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 SMA4S18AH reliable?
The price and inventory of SMA4S18AH are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMA4S18AH is usually 5 days.
3.What payment methods are accepted for SMA4S18AH?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMA4S18AH transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMA4S18AH?
SMA4S18AH orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMA4S18AH 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 SMA4S18AH?
For technical support, including SMA4S18AH datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMA4S18AH requirements.
6.How does Aetrix verify that SMA4S18AH is sourced from the original manufacturer or authorized distributors?
All SMA4S18AH 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 SMA4S18AH meets industry standards.
7.What is the process for return or replacement of SMA4S18AH?
All SMA4S18AH units undergo pre-shipment inspection (PSI). If there is an issue with SMA4S18AH, 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 SMA4S18AH part is unused and in its original packaging.
Return procedure for SMA4S18AH:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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