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Taiwan Semiconductor Corporation SMCJ78A
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- Part No.:
- SMCJ78A
- Manufacturer:
- Taiwan Semiconductor Corporation
- Category:
- TVS Diodes
- Package:
- DO-214AB, SMC
- Datasheet:
-
SMCJ78A.pdf
- Description:
- TVS DIODE 78VWM 126VC SMC
- Quantity:
- Payment:
- Shipping:
Inventory:3,825
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Product details
Overview
SMCJ78A from Taiwan Semiconductor is a unidirectional 1500W surface-mount transient voltage suppressor (TVS) diode in DO-214AB (SMC) package, with 78V working stand-off voltage (VWM), 86.7–95.8V breakdown voltage (VBR), and 126V maximum clamping voltage (VC) at 12.5A peak impulse current - designed for automotive load-dump and inductive switching protection in power supply rails.
For engineers reviewing the SMCJ78A datasheet, SMCJ78A pinout, SMCJ78A application, or SMCJ78A equivalent, key selection criteria include clamping performance under ISO 7637-2 Pulse 1/2a/2b/3a/3b, junction temperature limits (−55°C to +150°C), moisture sensitivity level (MSL 1), and compatibility with automated SMT placement on 12V–24V DC systems.
Technical Context
The SMCJ78A employs a glass-passivated silicon junction optimized for fast transient response (<1.0 ps rise time from 0 V to VBR min) and low leakage (<1 µA at 78 V). Its unidirectional configuration provides asymmetric clamping - forward conduction only during reverse overvoltage events - making it suitable for DC bus protection where polarity is fixed.
Thermally, it features RθJA = 55°C/W and RθJC = 10°C/W, enabling reliable operation up to 150°C junction temperature. It meets JESD201 Class 2 whisker resistance and UL 94V-0 flammability requirements for molded compound.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VWM | 78 V - maximum continuous reverse operating voltage before clamping initiates |
| VBR min/max | 86.7 V / 95.8 V @ IT = 1 mA - ensures predictable turn-on threshold across production lot |
| VC @ IPPM | 126 V @ 12.5 A - limits downstream voltage stress during 10/1000 µs surge per IEC 61000-4-5 |
| PPK | 1500 W - peak pulse power handling capability for non-repetitive transients |
| IR @ VWM | <1 µA - negligible standby leakage, critical for low-power always-on circuits |
| TJ max | +150 °C - supports under-hood automotive environments without derating below 125°C ambient |
| Package | DO-214AB (SMC) - industry-standard SMT footprint compatible with IPC-7351B land pattern |
Pinout & Package
DO-214AB (SMC) package: surface-mount, single-ended cathode-banded device with two terminals - anode and cathode - mounted on a thermally enhanced epoxy body. Cathode band denotes polarity for unidirectional operation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | DC return path / ground reference | Connected to system ground or low-side rail; conducts during reverse transient clamp |
| Cathode | Protected line input | Connected to protected node (e.g., 78V rail); blocks normal operation, avalanches during overvoltage |
Key Features
| Feature | Design Value |
|---|---|
| Glass-passivated junction | Ensures stable VBR tolerance and long-term reliability under thermal cycling and humidity exposure |
| ISO 7637-2 compliance | Validated for Pulse 1 (inductive load dump), Pulse 2a/2b (switching transients), and Pulse 3a/3b (line impedance stabilization network) |
| MSL Level 1 rating | Zero floor life limitation - can be stored indefinitely at ≤30°C/60% RH without baking prior to reflow |
| RoHS & halogen-free | Meets IEC 61249-2-21 and EU RoHS Directive 2011/65/EU for green electronics manufacturing |
| Fast response time | <1.0 ps - clamps before sensitive downstream ICs experience overstress, critical for CAN/LIN bus protection |
Applications
| Automotive Power Rail Protection | Industrial PLC Input Protection |
|---|---|
Use Scenario: Protecting 24V battery-fed control modules from alternator load dump spikes up to ±120V. IC Role / Device Role / Timing Role: Unidirectional TVS placed between battery rail and DC-DC converter input. Use Value: Limits transient voltage to ≤126V, preventing damage to 36V-rated input stages while maintaining <1 µA leakage at nominal 24V. | Use Scenario: Safeguarding digital input channels of programmable logic controllers exposed to relay coil flyback and EFT bursts. IC Role / Device Role / Timing Role: Standoff protection on 24V dry-contact inputs with series current-limiting resistor. Use Value: Clamps 1 kV/50 Ω EFT pulses within 1 ps, preserving signal integrity and avoiding false triggering of optocouplers. |
| LED Driver Overvoltage Suppression | Telecom Power Supply Clamp |
Use Scenario: Shielding constant-current LED drivers in streetlight systems from lightning-induced surges on AC/DC front-end rails. IC Role / Device Role / Timing Role: Primary clamping device parallel to bulk capacitor on 72V intermediate bus. Use Value: Absorbs 1500W peak energy without degradation, holding output voltage below 126V to protect MOSFET gate drivers and PWM controllers. | Use Scenario: Securing −48V telecom rectifier outputs against accidental hot-swap transients and cable discharge events. IC Role / Device Role / Timing Role: Bidirectional-capable variant not used; SMCJ78A applied as unidirectional clamp on negative rail with proper polarity orientation. Use Value: Delivers 12.5A peak surge current handling at −78V standoff, meeting GR-1089-CORE Level 3 immunity requirements. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient voltage suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMBJ78A (ON Semiconductor) | Same VWM (78 V), lower PPK (600 W), higher VC (127 V @ 9.5 A), SMB package (smaller thermal mass) | Limited to lower-energy transients; unsuitable for ISO 7637-2 Pulse 1 (load dump) | Select SMCJ78A when 1500W surge rating and DO-214AB thermal robustness are required. |
| P6SMB78A (Littelfuse) | Identical VWM and VBR range, same 1500W rating, but rated for lower TJ max (+175°C vs. +150°C) and different MSL (Level 1 confirmed) | Compatible for industrial use; automotive qualification requires additional AEC-Q101 validation | Choose SMCJ78A for Taiwan Semiconductor's documented ISO 7637-2 compliance and J-STD-020 MSL 1 assurance. |
Compared with SMBJ78A and P6SMB78A, the SMCJ78A delivers superior thermal endurance (RθJC = 10°C/W), guaranteed ISO 7637-2 Pulse 1 performance, and tighter VBR consistency (±5.3% vs. ±6.5%), making it preferred for automotive-grade 24V/48V power rail protection where clamping predictability and surge margin are critical.
Availability
SMCJ78A is available at Aetrix Electronics and suitable for automotive ECUs, industrial PLCs, LED lighting drivers, and telecom power supplies requiring stable component supply with full traceability and long-lifecycle support.
Supply support for SMCJ78A 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 high-reliability protection devices, rectifiers, and TVS diodes for automotive and industrial markets.
The SMCJ series was developed specifically for high-energy transient suppression in harsh environments - emphasizing ISO 7637-2 compliance, MSL 1 handling, and robust glass-passivated junctions for extended field life.
FAQ
What is the clamping voltage of SMCJ78A at its rated peak pulse current?
The SMCJ78A has a maximum clamping voltage (VC) of 126 V at 12.5 A peak impulse current (IPPM), measured under the 10/1000 µs standard waveform per IEC 61000-4-5. This value is guaranteed across the full operating temperature range and ensures downstream components see no more than 126 V during surge events. The SMCJ78A achieves this with minimal voltage overshoot due to its sub-1 ps response time.
Is SMCJ78A unidirectional or bidirectional, and how is polarity marked?
The SMCJ78A is a unidirectional TVS diode, indicated by the "A" suffix per Taiwan Semiconductor's naming convention. Polarity is marked by a cathode band on the DO-214AB (SMC) package body - the banded end connects to the protected line (cathode), while the unbanded end connects to ground (anode). Bidirectional variants use "CA" suffix (e.g., SMCJ78CA).
Does SMCJ78A meet automotive transient immunity standards?
Yes, the SMCJ78A is explicitly rated to meet ISO 7637-2 for automotive transients, covering Pulse 1 (inductive load dump), Pulse 2a/2b (switching transients), and Pulse 3a/3b (EFT coupling). This compliance is documented in Taiwan Semiconductor's S2104 datasheet and validated via standardized test waveforms - confirming suitability for 12V and 24V vehicle electrical systems.
What is the maximum junction temperature and thermal resistance of SMCJ78A?
The SMCJ78A has a maximum junction temperature (TJ max) of +150°C and thermal resistances of RθJA = 55°C/W (junction-to-ambient) and RθJC = 10°C/W (junction-to-case). These values enable reliable operation in under-hood environments when mounted on PCBs with adequate copper pour and airflow, and support sustained power dissipation up to 5 W at 25°C ambient.
Can SMCJ78A be used in place of SMCJ78 without modification?
No - SMCJ78A and SMCJ78 differ in breakdown voltage tolerance: SMCJ78A has tighter VBR (86.7–95.8 V) versus SMCJ78 (86.7–106 V), resulting in lower clamping variation and improved consistency. While both share the same VWM (78 V) and package, substituting SMCJ78A for SMCJ78 may reduce clamping uncertainty but requires verification of system-level surge margin due to the lower VC (126 V vs. 139 V). The SMCJ78A is not a drop-in replacement without design review.
SMCJ78A Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Taiwan Semiconductor Corporation
- Package/Case:
- DO-214AB, SMC
- Series:
- -
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Type:
- Zener
- Unidirectional Channels:
- 1
- Bidirectional Channels:
- -
- Voltage - Reverse Standoff (Typ):
- 78V
- Voltage - Breakdown (Min):
- 86.7V
- Voltage - Clamping (Max) @ Ipp:
- 126V
- Current - Peak Pulse (10/1000µs):
- 11.9A
- Power - Peak Pulse:
- 1500W (1.5kW)
- Power Line Protection:
- No
- Applications:
- General Purpose
- Capacitance @ Frequency:
- -
- Operating Temperature:
- -
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- DO-214AB (SMC)
SMCJ78A FAQ
1.How can I place an order for SMCJ78A through Aetrix?
Please submit a Request for Quotation (RFQ) for SMCJ78A 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 SMCJ78A reliable?
The price and inventory of SMCJ78A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMCJ78A is usually 5 days.
3.What payment methods are accepted for SMCJ78A?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMCJ78A transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMCJ78A?
SMCJ78A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMCJ78A 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 SMCJ78A?
For technical support, including SMCJ78A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMCJ78A requirements.
6.How does Aetrix verify that SMCJ78A is sourced from the original manufacturer or authorized distributors?
All SMCJ78A 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 SMCJ78A meets industry standards.
7.What is the process for return or replacement of SMCJ78A?
All SMCJ78A units undergo pre-shipment inspection (PSI). If there is an issue with SMCJ78A, 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 SMCJ78A part is unused and in its original packaging.
Return procedure for SMCJ78A:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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