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Taiwan Semiconductor Corporation SMAJ78CA
- Part No.:
- SMAJ78CA
- Manufacturer:
- Taiwan Semiconductor Corporation
- Category:
- TVS Diodes
- Package:
- DO-214AC, SMA
- Datasheet:
-
SMAJ78CA.pdf
- Description:
- TVS DIODE 78VWM 126VC DO214AC
- Quantity:
- Payment:
- Shipping:
Inventory:6,804
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Product details
Overview
SMAJ78CA from Taiwan Semiconductor is a bidirectional 400W transient voltage suppressor (TVS) diode in DO-214AC (SMA) package, designed for clamping fast transients in DC power rails. It features a 78V working stand-off voltage (VWM), 86.7–106V breakdown voltage (VBR) at 1mA test current, and clamps to ≤126V at 3.2A peak impulse current under 10/1000μs waveform - used in automotive power supply protection and industrial DC/DC converters.
For engineers reviewing the SMAJ78CA datasheet, SMAJ78CA pinout, SMAJ78CA application, or SMAJ78CA equivalent, key selection criteria include bidirectional clamping capability, ISO 7637-2 Pulse 1/2a/2b/3a/3b compliance, moisture sensitivity level 1 rating, and verified 150°C maximum junction temperature operation.
Technical Context
The SMAJ78CA is a glass-passivated, single-die, bidirectional TVS diode optimized for high-energy surge suppression on unregulated or lightly regulated DC lines. Its sub-1ps response time ensures clamping before sensitive downstream circuitry sustains damage, and its low leakage (<1µA at VWM) minimizes standby power loss in always-on systems.
Rated for 400W peak pulse power (10/1000μs), it delivers 300W+ above 78V per specification - confirming robustness against load dump and inductive switching events. The device operates across –55°C to +150°C and meets JESD201 Class 2 whisker resistance and UL 94V-0 flammability standards.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VWM | 78 V - Maximum continuous reverse operating voltage before significant leakage begins; sets safe DC rail margin. |
| VBR @ IT=1mA | 86.7–106 V - Breakdown threshold range; guarantees reliable turn-on during overvoltage events. |
| VC @ IPPM=3.2A | ≤126 V - Clamped voltage under 10/1000μs surge; defines worst-case stress on protected ICs. |
| PPPM | 400 W (10/1000μs) - Peak surge energy handling capacity; sufficient for ISO 7637-2 Pulse 5a load dump simulation. |
| IR @ VWM | <1 µA - Ultra-low reverse leakage; avoids battery drain in automotive always-on modules. |
| TJ max | +150 °C - Enables placement near hot components (e.g., MOSFETs, inductors) without thermal derating concerns. |
| Package | DO-214AC (SMA) - Industry-standard surface-mount outline with 0.060g mass; compatible with automated pick-and-place. |
Pinout & Package
DO-214AC (SMA) package: molded plastic case with matte tin-plated leads, polarity indicated by cathode band (bidirectional symmetry means both terminals are functionally identical).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode / Cathode (symmetrical) | Bidirectional surge path | Either terminal serves as input/output for transient energy; no polarity dependency in layout. |
| Case | Non-connected mechanical body | No internal thermal or electrical connection to die; mounting pad provides only mechanical stability and limited heat sinking. |
Key Features
| Feature | Design Value |
|---|---|
| ISO 7637-2 compliance | Validated for Pulse 1 (inductive spike), Pulse 2a/2b (battery disconnect), and Pulse 3a/3b (switching noise) - enables drop-in use in automotive ECUs. |
| Moisture sensitivity level 1 | No floor life limitation or bake requirement before reflow; simplifies SMT line logistics and reduces handling cost. |
| Glass-passivated junction | Enhances long-term reliability under thermal cycling and humidity exposure - critical for under-hood automotive applications. |
| Fast response time <1 ps | Clamps before ESD or lightning-induced transients propagate beyond PCB traces - protects high-speed logic and analog front-ends. |
| Halogen-free & RoHS compliant | Meets IEC 61249-2-21 and EU Directive 2011/65/EU - supports green manufacturing and export compliance. |
Applications
| Automotive Body Control Module (BCM) | Industrial DC/DC Converter Input Stage |
|---|---|
Use Scenario: Protects microcontroller I/O and CAN transceiver power rails from load dump and jump-start surges in 12V vehicle systems. IC Role / Device Role / Timing Role: Bidirectional clamping element placed directly at connector entry point to shunt transient energy to ground before reaching LDOs or regulators. Use Value: Withstands 400W pulses and clamps to ≤126V, ensuring downstream 3.3V/5V logic remains within absolute maximum ratings during ISO 7637-2 Pulse 5a events. |
Use Scenario: Shields isolated flyback or buck-boost converter inputs from AC line transients and field wiring in factory automation equipment. IC Role / Device Role / Timing Role: Primary overvoltage clamp on unregulated 24–48V DC bus, coordinated with upstream fuse and downstream TVS arrays. Use Value: Low 1µA leakage preserves efficiency in 24/7 operation; DO-214AC footprint allows dense layout without compromising creepage/clearance. |
| LED Streetlight Driver | Telecom Power Shelf Input Protection |
Use Scenario: Guards constant-current LED driver ICs against lightning-induced surges on outdoor-rated 120–350V DC distribution lines. IC Role / Device Role / Timing Role: First-line transient absorber mounted adjacent to input terminals, preceding bulk capacitor and PFC stage. Use Value: 150°C TJ rating supports operation inside thermally constrained aluminum housings; halogen-free construction meets outdoor environmental mandates. |
Use Scenario: Safeguards -48V telecom rectifier outputs from backfeed transients and hot-swap induced spikes in central office power systems. IC Role / Device Role / Timing Role: Bidirectional clamp on distributed -48V bus, placed before DC-DC modules supplying FPGA, PHY, and control logic. Use Value: Sub-1ps response prevents latch-up in sensitive SerDes interfaces; MSL-1 qualification eliminates pre-reflow baking in high-volume telecom assembly. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMBJ78CA (Bourns) | Same VWM/VBR range but rated for 600W peak power (10/1000μs); larger SMB package (DO-214AA). | Higher power handling suits higher-energy environments (e.g., heavy-duty truck 24V systems), but requires PCB layout change. | Select SMBJ78CA when system-level surge testing exceeds 400W or when thermal margin must be increased via larger copper area. |
| P6SMB78CA (Littelfuse) | Identical electrical specs and DO-214AC package; same 400W rating, 78V VWM, and 126V clamping; minor differences in IR distribution and lead finish. | No functional or mechanical deviation - validated as second-source replacement in multiple AEC-Q200-qualified designs. | Choose P6SMB78CA for dual-sourcing continuity or where Littelfuse's supply chain alignment better matches production ramp timing. |
Compared with SMBJ78CA and P6SMB78CA, the SMAJ78CA offers identical protection performance in the smallest standard surface-mount TVS footprint (DO-214AC), making it optimal for space-constrained automotive and industrial PCBs where 400W surge immunity suffices.
Availability
SMAJ78CA is available at Aetrix Electronics and suitable for automotive body electronics, industrial DC/DC converters, and outdoor LED lighting requiring stable component supply with full traceability and lifecycle management.
Supply support for SMAJ78CA 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 ISO/TS 16949 and IATF 16949 certification for automotive-grade products.
The SMAJ series was developed specifically for high-reliability transient suppression in harsh-environment applications - emphasizing fast response, low leakage, and robust packaging for automotive, industrial, and telecom infrastructure.
FAQ
What is the clamping voltage of SMAJ78CA at its rated peak pulse current?
The SMAJ78CA clamps to a maximum of 126 V when subjected to its rated peak impulse current of 3.2 A under the standardized 10/1000 μs waveform. This value is measured per the manufacturer's test conditions and defines the upper voltage limit imposed on protected circuitry during surge events - critical for ensuring downstream ICs remain within their absolute maximum ratings.
Is SMAJ78CA unidirectional or bidirectional, and how is polarity marked?
SMAJ78CA is a bidirectional TVS diode, indicated by the "CA" suffix per Taiwan Semiconductor's naming convention. Unlike unidirectional variants (e.g., SMAJ78A), it has symmetrical breakdown behavior in both directions and carries no cathode band marking - both terminals are electrically identical, eliminating orientation constraints during PCB layout and assembly.
Does SMAJ78CA meet automotive transient immunity standards?
Yes, SMAJ78CA meets ISO 7637-2 requirements for Pulse 1 (inductive switch-off), Pulse 2a/2b (battery disconnection), and Pulse 3a/3b (capacitive coupling), as explicitly stated in the official datasheet. Its 400W peak pulse rating and fast <1 ps response make it suitable for protecting ECUs, body control modules, and infotainment power supplies in 12V and 24V vehicle architectures.
What is the maximum junction temperature and thermal derating behavior of SMAJ78CA?
The SMAJ78CA has a maximum junction temperature (TJ) of +150°C and follows standard thermal derating curves per Figure 2 in the datasheet: peak pulse power decreases linearly above 25°C ambient, reaching ~240W at +85°C and ~120W at +125°C. This allows reliable operation in under-hood or enclosed industrial enclosures without forced cooling.
How does SMAJ78CA compare to SMAJ78A in terms of electrical performance?
SMAJ78CA is bidirectional with symmetrical VBR (86.7–106 V) and clamping in both polarities, while SMAJ78A is unidirectional and only clamps in reverse bias. SMAJ78CA's VC is 126 V vs. SMAJ78A's 139 V, reflecting tighter clamping due to bidirectional design optimization - making SMAJ78CA preferable for AC-coupled or polarity-agnostic DC protection scenarios.
SMAJ78CA 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:
- General Purpose
- Capacitance @ Frequency:
- -
- Operating Temperature:
- -55°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- DO-214AC (SMA)
SMAJ78CA FAQ
1.How can I place an order for SMAJ78CA through Aetrix?
Please submit a Request for Quotation (RFQ) for SMAJ78CA 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 SMAJ78CA reliable?
The price and inventory of SMAJ78CA are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMAJ78CA is usually 5 days.
3.What payment methods are accepted for SMAJ78CA?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMAJ78CA transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMAJ78CA?
SMAJ78CA orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMAJ78CA 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 SMAJ78CA?
For technical support, including SMAJ78CA datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMAJ78CA requirements.
6.How does Aetrix verify that SMAJ78CA is sourced from the original manufacturer or authorized distributors?
All SMAJ78CA 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 SMAJ78CA meets industry standards.
7.What is the process for return or replacement of SMAJ78CA?
All SMAJ78CA units undergo pre-shipment inspection (PSI). If there is an issue with SMAJ78CA, 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 SMAJ78CA part is unused and in its original packaging.
Return procedure for SMAJ78CA:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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