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Taiwan Semiconductor Corporation SMAJ78CAH
- Part No.:
- SMAJ78CAH
- Manufacturer:
- Taiwan Semiconductor Corporation
- Category:
- TVS Diodes
- Package:
- DO-214AC, SMA
- Datasheet:
-
SMAJ78CAH.pdf
- Description:
- TVS DIODE 78VWM 126VC DO214AC
- Quantity:
- Payment:
- Shipping:
Inventory:5,305
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Product details
Overview
SMAJ78CAH from Taiwan Semiconductor is a bidirectional 78V standoff transient voltage suppressor (TVS) diode in DO-214AC (SMA) package, rated for 400W peak pulse power (10/1000μs), clamping to 126V at 3.2A, and qualified to AEC-Q101 for automotive-grade reliability. It protects DC/DC converters and SMPS inputs against ISO 7637-2 Pulse 1/2a/2b/3a/3b transients.
For engineers reviewing the SMAJ78CAH datasheet, SMAJ78CAH pinout, SMAJ78CAH application, or SMAJ78CAH equivalent, key selection criteria include its bidirectional configuration, 78V working voltage, 126V clamping voltage at 3.2A, AEC-Q101 qualification, and DO-214AC mechanical compatibility with automated SMT placement.
Technical Context
The SMAJ78CAH is a glass-passivated, single-die, bidirectional TVS diode designed for unidirectional or bidirectional surge suppression in automotive and industrial power rails. Its junction operates from –55°C to +150°C, with <1μA reverse leakage at 78V and sub-1ps response time from 0V to breakdown.
It delivers 400W peak pulse power per 10/1000μs waveform up to 78V, derating linearly above 25°C ambient per Fig.2; clamping performance is specified at 3.2A IPPM with VC = 126V, and it meets moisture sensitivity level 1 per J-STD-020.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VWM | 78 V - Maximum continuous reverse operating voltage before clamping begins |
| VBR min / max | 86.7 V / 95.8 V - Breakdown occurs within this range at 1 mA test current, ensuring predictable turn-on |
| VC @ IPPM | 126 V @ 3.2 A - Clamping voltage during 10/1000μs surge, limiting downstream voltage stress |
| PPPM | 400 W - Peak surge energy absorption capability under standard 10/1000μs waveform |
| IR @ VWM | <1 μA - Negligible leakage at rated standoff voltage, minimizing standby power loss |
| Package | DO-214AC (SMA) - Surface-mount outline with 0.060g mass, UL 94V-0 molding, matte tin leads |
| AEC-Q101 | Qualified - Validated for automotive applications including temperature cycling, HTRB, and ESD |
Pinout & Package
DO-214AC (SMA) package: molded plastic case with cathode band marking; bidirectional symmetry means both terminals are functionally identical-no polarity-dependent orientation required in circuit layout.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode/Cathode (symmetrical) | Transient conduction path | Both terminals serve as interchangeable surge current entry/exit points; no DC polarity dependency |
| Cathode band (marking) | Manufacturing polarity indicator | Present for traceability only; irrelevant for electrical function in bidirectional SMAJ78CAH |
Key Features
| Feature | Design Value |
|---|---|
| AEC-Q101 qualification | Validated for automotive underhood environments including thermal cycling, high-temp reverse bias, and mechanical shock |
| Glass-passivated junction | Enhances long-term reliability and stability of breakdown voltage under humidity and thermal stress |
| Sub-1ps response time | Clamps transients before sensitive downstream ICs experience overvoltage damage |
| ISO 7637-2 compliance | Withstands standardized automotive load dump and inductive switching pulses (Pulse 1/2a/2b/3a/3b) |
| Moisture sensitivity level 1 | Zero bake requirement prior to reflow; compatible with standard SMT assembly without floor-life restrictions |
Applications
| Automotive Infotainment Power Rail | Industrial PLC I/O Protection |
|---|---|
Use Scenario: Protects 12V/24V supply inputs of head units and display modules from alternator load dump and inductive kickback. IC Role / Device Role / Timing Role: Bidirectional clamping device placed upstream of DC/DC regulators and LDOs. Use Value: Limits transient voltage to ≤126V, preventing latch-up or permanent damage to PMICs and microcontrollers. |
Use Scenario: Shields digital input/output channels on programmable logic controllers from field-wiring surges and ESD events. IC Role / Device Role / Timing Role: Primary overvoltage clamp on 24V sensor/actuator interface lines. Use Value: Absorbs 400W surges without degradation, maintaining signal integrity and system uptime in factory environments. |
| On-Board EV Charger DC Link | LED Streetlight Driver Input |
Use Scenario: Guards high-voltage DC bus monitoring circuits in vehicle-mounted AC/DC chargers against grid-side transients. IC Role / Device Role / Timing Role: Secondary-level transient suppressor across isolated sensing inputs referenced to chassis ground. Use Value: Provides 126V clamping with <1μA leakage, enabling accurate voltage measurement while surviving repeated 10/1000μs surges. |
Use Scenario: Safeguards constant-current LED driver ICs in outdoor lighting against lightning-induced line surges. IC Role / Device Role / Timing Role: First-line protection on AC-DC rectified output rail before bulk capacitor and controller. Use Value: Delivers 400W pulse handling in compact SMA package, reducing board area vs. larger DO-214AB alternatives. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| Littelfuse SMAJ78CA | Identical electrical specs (VWM=78V, [email protected]), same DO-214AC package, but not AEC-Q101 qualified | Not suitable for automotive OEM or Tier-1 designs requiring AEC-Q101 evidence | Select SMAJ78CAH when automotive qualification and full ISO 7637-2 validation are mandatory |
| Vishay SMAJ78CA-E3/5A | Same VWM/VC ratings and package; IR spec is ≤1μA (identical), but peak power rated at 300W above 78V per datasheet footnote | Lower pulse power margin may limit robustness in high-energy load dump scenarios | Prefer SMAJ78CAH where full 400W rating at 78V is required per design margin analysis |
Compared with Littelfuse SMAJ78CA and Vishay SMAJ78CA-E3/5A, the SMAJ78CAH provides verified AEC-Q101 qualification and guaranteed 400W peak pulse power at 78V-critical for automotive power rail protection where reliability and specification margin directly impact field failure rates.
Availability
SMAJ78CAH is available at Aetrix Electronics and suitable for automotive infotainment systems, industrial PLC I/O modules, and LED streetlight drivers requiring stable component supply with full AEC-Q101 traceability and ISO 7637-2 compliance.
Supply support for SMAJ78CAH 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, and power MOSFETs for automotive and industrial markets.
The SMAJ series was developed specifically for high-reliability transient suppression in automotive power systems, emphasizing AEC-Q101 qualification, tight parameter distribution, and robust surge endurance in DO-214AC packaging.
FAQ
What does the "CAH" suffix indicate in SMAJ78CAH?
The "CAH" suffix denotes a bidirectional configuration ("C"), AEC-Q101 qualification ("A"), and halogen-free construction ("H"). Unlike unidirectional variants (e.g., SMAJ78AH), SMAJ78CAH provides symmetrical clamping in both polarities-essential for AC-coupled or floating-rail protection without polarity concerns.
Is SMAJ78CAH pin-compatible with SMAJ78AH?
No-SMAJ78CAH is bidirectional while SMAJ78AH is unidirectional. Though both use DO-214AC packaging and share identical physical pinout, SMAJ78AH requires correct cathode orientation in-circuit, whereas SMAJ78CAH has no functional polarity. Layout reuse is possible only if the original design accommodates bidirectional behavior.
What is the maximum clamping voltage of SMAJ78CAH under surge conditions?
The maximum clamping voltage of SMAJ78CAH is 126 V, measured at 3.2 A peak impulse current (IPPM) using the standardized 10/1000μs waveform. This value is guaranteed across temperature and lifetime, ensuring consistent overvoltage protection for downstream components.
Does SMAJ78CAH meet ISO 7637-2 requirements?
Yes-SMAJ78CAH is explicitly validated to meet ISO 7637-2 Pulse 1, 2a, 2b, 3a, and 3b test profiles. Its 400W peak pulse rating, fast response (<1ps), and low clamping voltage enable reliable suppression of automotive conducted transients without additional external circuitry.
What is the junction temperature limit for SMAJ78CAH?
The maximum operating junction temperature for SMAJ78CAH is +150°C, with a storage temperature range of –55°C to +150°C. Derating of peak pulse power begins above 25°C ambient per the published pulse derating curve (Fig.2), supporting operation in under-hood automotive environments.
SMAJ78CAH 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):
- 78V
- Voltage - Breakdown (Min):
- 86.7V
- Voltage - Clamping (Max) @ Ipp:
- 126V
- Current - Peak Pulse (10/1000µs):
- 3.2A
- 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)
SMAJ78CAH FAQ
1.How can I place an order for SMAJ78CAH through Aetrix?
Please submit a Request for Quotation (RFQ) for SMAJ78CAH 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 SMAJ78CAH reliable?
The price and inventory of SMAJ78CAH are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMAJ78CAH is usually 5 days.
3.What payment methods are accepted for SMAJ78CAH?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMAJ78CAH transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMAJ78CAH?
SMAJ78CAH orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMAJ78CAH 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 SMAJ78CAH?
For technical support, including SMAJ78CAH datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMAJ78CAH requirements.
6.How does Aetrix verify that SMAJ78CAH is sourced from the original manufacturer or authorized distributors?
All SMAJ78CAH 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 SMAJ78CAH meets industry standards.
7.What is the process for return or replacement of SMAJ78CAH?
All SMAJ78CAH units undergo pre-shipment inspection (PSI). If there is an issue with SMAJ78CAH, 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 SMAJ78CAH part is unused and in its original packaging.
Return procedure for SMAJ78CAH:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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