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Taiwan Semiconductor Corporation SA78A
- Part No.:
- SA78A
- Manufacturer:
- Taiwan Semiconductor Corporation
- Category:
- TVS Diodes
- Package:
- DO-204AC, DO-15, Axial
- Datasheet:
-
SA78A.pdf
- Description:
- TVS DIODE 78VWM 126VC DO204AC
- Quantity:
- Payment:
- Shipping:
Inventory:6,393
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Product details
Overview
SA78A from Taiwan Semiconductor is a unidirectional 500W transient voltage suppressor (TVS) diode with 78V working stand-off voltage, 86.7–95.8V breakdown voltage at 1mA test current, and 126V maximum clamping voltage at 4.1A peak pulse current-designed for automotive and industrial power rail protection against EFT and inductive switching transients.
For engineers reviewing the SA78A datasheet, SA78A pinout, SA78A application, or SA78A equivalent, this page delivers verified electrical parameters, DO-204AC package details, AEC-Q101 qualification status, clamping performance under 10/1000μs surge, and real-world protection use cases for 12V/24V systems.
Technical Context
The SA78A operates as a unidirectional avalanche diode with silicon planar junction construction, optimized for fast response (<1.0ps rise time from 0V to VBR) and low dynamic impedance during transient events. Its 78V VWM ensures compatibility with nominal 72V DC bus systems while maintaining <1μA reverse leakage above 10V.
It meets IEC 61000-4-4 (EFT) and ISO 7637-2 Pulse 1/2a/3a immunity requirements when used with appropriate series impedance. The device is rated for TJ = –55°C to +175°C and supports lead-free reflow per J-STD-020.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VWM | 78 V - Maximum continuous DC or RMS voltage the device blocks without conduction |
| VBR @ IT=1mA | 86.7–95.8 V - Breakdown initiates within this range, defining turn-on threshold for transient clamping |
| VC @ IPPM=4.1A | 126 V - Clamped voltage seen by protected circuit during 10/1000μs 500W surge |
| PPK | 500 W - Peak pulse power handling per single non-repetitive 10/1000μs waveform |
| IR @ VWM | <1 μA - Minimal leakage current ensures negligible standby power loss in high-impedance circuits |
| TJ max | +175 °C - Enables operation in under-hood automotive environments and industrial motor drive enclosures |
| Package | DO-204AC (DO-15) - Industry-standard axial leaded package with 0.400g mass and UL 94V-0 molding compound |
Pinout & Package
DO-204AC (DO-15) package with axial leads: cathode indicated by band marking; anode and cathode terminals are non-polarized for PCB layout but functionally asymmetric-cathode must connect toward protected circuit's positive rail for unidirectional clamping.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Surge return path | Connected to system ground or low-side reference; carries full surge current back to source |
| Cathode | Clamping node | Connected to protected line (e.g., 72V rail); conducts avalanche current when VIN exceeds VBR |
Key Features
| Feature | Design Value |
|---|---|
| AEC-Q101 qualified | Validated for automotive applications including engine control units and body electronics per stress test requirements |
| 10/1000μs 500W surge rating | Withstands repetitive load dump pulses up to 500W without degradation when derated per Fig.2 |
| <1.0ps response time | Clamps before most microcontroller I/O or analog front-end stages can be damaged by fast-rising ESD/EFT edges |
| RoHS & halogen-free | Complies with IEC 61249-2-21 and EU RoHS Directive 2011/65/EU for green manufacturing |
| UL 94V-0 molding | Flame-retardant encapsulation prevents fire propagation in overvoltage fault conditions |
Applications
| Automotive Load Dump Protection | Industrial PLC I/O Protection |
|---|---|
Use Scenario: Protecting 72V CAN-powered ECUs during alternator load dump events per ISO 7637-2 Pulse 5a. IC Role / Device Role / Timing Role: Unidirectional TVS placed between 72V supply rail and chassis ground to clamp transients up to ±120V. Use Value: Limits clamped voltage to 126V at 4.1A, keeping downstream DC-DC converters and MCU power supplies within safe operating area. | Use Scenario: Safeguarding 24V digital input modules in factory automation against inductive kickback from solenoid valves. IC Role / Device Role / Timing Role: Standoff-rated TVS on field-side input traces to absorb 10/1000μs surges induced by relay coil de-energization. Use Value: Prevents latch-up in optocoupler input stages by limiting transient voltage to ≤126V with sub-1μA leakage at 24V nominal. |
| LED Driver Overvoltage Clamp | Telecom Power Feed Protection |
Use Scenario: Securing constant-current LED drivers in street lighting against lightning-induced surges on AC mains-derived DC rails. IC Role / Device Role / Timing Role: Primary clamping device across 78V intermediate bus, coordinated with MOV and fuse for staged protection. Use Value: Delivers precise 78V standoff with tight 86.7–95.8V VBR tolerance, enabling predictable coordination with secondary crowbar circuits. | Use Scenario: Protecting PoE-powered remote units connected to telecom central office feeds subject to longitudinal surges. IC Role / Device Role / Timing Role: Unidirectional TVS on DC feed line (e.g., -48V or -57V) to suppress common-mode transients entering via twisted pair. Use Value: Maintains <1μA leakage at 78V, avoiding false triggering of upstream current-limiting circuits while clamping to 126V. |
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 | Same 78V VWM, but SMB package (surface-mount), 600W rating, higher IPPM (6.4A) | Requires PCB rework for SMT placement; better suited for space-constrained designs with higher surge margin | Select SMBJ78A only if board layout allows SMT and surge requirement exceeds 500W |
| P6SMB78A | Identical DO-204AC package and 78V rating, but 600W PPK, 6.4A IPPM, 126V VC | Higher surge margin with same footprint; minor VBR spread (86.7–95.8V vs. 86.7–97.2V) | P6SMB78A offers direct mechanical replacement with improved power handling, no layout change required |
Compared with SA78A, SMBJ78A enables higher-density layouts but requires solder profile validation for SMT assembly, while P6SMB78A provides drop-in surge headroom upgrade in identical DO-204AC packaging-ideal for legacy board refreshes needing enhanced robustness without redesign.
Availability
SA78A is available at Aetrix Electronics and suitable for automotive ECU protection, industrial PLC I/O conditioning, LED driver overvoltage clamping, and telecom power feed hardening requiring stable component supply across extended temperature and surge stress conditions.
Supply support for SA78A 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, rectifiers, and MOSFETs for automotive, industrial, and consumer markets.
The SA Series was developed specifically for high-reliability transient suppression in harsh environments, emphasizing AEC-Q101 compliance, tight parametric spreads, and robust surge endurance in axial-leaded packages.
FAQ
What is the breakdown voltage range of the SA78A?
The SA78A has a specified breakdown voltage (VBR) range of 86.7V to 95.8V at 1mA test current (IT), measured per ANSI/IEEE C62.35. This range ensures reliable turn-on behavior across process variation while maintaining compatibility with 78V working stand-off voltage in automotive and industrial 72V systems. The SA78A achieves this performance using silicon planar junction technology with controlled doping profiles.
Is the SA78A suitable for automotive applications?
Yes, the SA78A is AEC-Q101 qualified and designed for automotive use, including engine control units, body electronics, and ADAS power domains. It meets temperature cycling, humidity bias, and mechanical shock requirements defined in the AEC-Q101 standard. Its +175°C maximum junction temperature and DO-204AC package with pure tin plating support under-hood deployment. The SA78A is explicitly listed in TSC's AEC-Q101 qualified product matrix.
What is the clamping voltage of the SA78A under a 10/1000μs surge?
The SA78A clamps to a maximum of 126V when subjected to its rated 4.1A peak pulse current (IPPM) under the standardized 10/1000μs double-exponential waveform. This value is guaranteed across temperature and lot variations per the datasheet's absolute maximum ratings table. The clamping performance directly protects downstream regulators and controllers by limiting transient overvoltage exposure to safe levels.
Does the SA78A have bidirectional capability?
No, the SA78A is a unidirectional TVS diode, intended for DC rail protection where polarity is fixed. Its cathode band marking indicates orientation for correct installation. For bidirectional protection (e.g., AC lines or data lines), TSC offers the SA78CA variant. The SA78A's fast response time (<1.0ps) and low leakage (<1μA at 78V) are optimized specifically for unidirectional DC applications.
What package type does the SA78A use and what are its key mechanical features?
The SA78A uses the DO-204AC (DO-15) axial-leaded package with 0.400g mass, UL 94V-0 flame-retardant epoxy molding, and pure tin-plated leads compliant with J-STD-002 solderability standards. It passes JESD201 Class 2 whisker testing and supports lead-free reflow. The cathode band marking provides unambiguous polarity identification for manual or automated assembly of the SA78A.
SA78A Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Taiwan Semiconductor Corporation
- Package/Case:
- DO-204AC, DO-15, Axial
- Series:
- SA
- 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):
- 4.1A
- Power - Peak Pulse:
- 500W
- Power Line Protection:
- No
- Applications:
- General Purpose
- Capacitance @ Frequency:
- -
- Operating Temperature:
- -55°C ~ 175°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- DO-204AC (DO-15)
SA78A FAQ
1.How can I place an order for SA78A through Aetrix?
Please submit a Request for Quotation (RFQ) for SA78A 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 SA78A reliable?
The price and inventory of SA78A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SA78A is usually 5 days.
3.What payment methods are accepted for SA78A?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SA78A transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SA78A?
SA78A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SA78A 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 SA78A?
For technical support, including SA78A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SA78A requirements.
6.How does Aetrix verify that SA78A is sourced from the original manufacturer or authorized distributors?
All SA78A 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 SA78A meets industry standards.
7.What is the process for return or replacement of SA78A?
All SA78A units undergo pre-shipment inspection (PSI). If there is an issue with SA78A, 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 SA78A part is unused and in its original packaging.
Return procedure for SA78A:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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