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Taiwan Semiconductor Corporation SA78
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- Part No.:
- SA78
- Manufacturer:
- Taiwan Semiconductor Corporation
- Category:
- TVS Diodes
- Package:
- DO-204AC, DO-15, Axial
- Datasheet:
-
SA78.pdf
- Description:
- 500W, 94.9V, 10%, UNIDIRECTIONAL
- Quantity:
- Payment:
- Shipping:
Inventory:8,542
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Product details
Overview
SA78 from Taiwan Semiconductor is a unidirectional 500W transient voltage suppressor (TVS) diode in DO-204AC (DO-15) package, with 78V working stand-off voltage (VWM), 86.7–103V breakdown voltage (VBR @ 1mA), and 139V maximum clamping voltage (VC) at 3.7A peak pulse current. It delivers fast response (<1.0ps), low leakage (<1μA @ 78V), and AEC-Q101 qualification for automotive-grade surge protection.
For engineers reviewing the SA78 datasheet, SA78 pinout, SA78 application, or SA78 equivalent, this device is selected for high-reliability DC power rail and signal line protection where precise 78V standoff, sub-140V clamping under 10/1000μs transients, thermal stability to +175°C, and RoHS/halogen-free compliance are required.
Technical Context
The SA78 operates as a silicon avalanche diode, triggered when reverse voltage exceeds its specified VBR range (86.7–103V @ 1mA). Its unidirectional polarity enables asymmetric clamping-blocking forward conduction above ~3.5V while suppressing negative transients to ≤139V at 3.7A.
Designed for non-repetitive 10/1000μs surge waveforms, it sustains 500W peak pulse power at 25°C with derating above ambient, and supports steady-state dissipation of 3W at TL = 75°C on 10×10 mm copper pads. Junction temperature range is –55°C to +175°C.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VWM | 78 V - Maximum continuous reverse operating voltage before clamping begins; defines safe DC bias margin. |
| VBR min/max | 86.7 / 103 V @ 1 mA - Breakdown threshold range; ensures reliable turn-on across process variation and temperature. |
| VC @ IPPM | 139 V @ 3.7 A - Clamped voltage during 10/1000μs surge; limits downstream IC stress to safe levels. |
| PPK | 500 W - Peak pulse power rating at TA = 25°C; determines single-event surge energy handling capability. |
| IR @ VWM | <1 μA - Reverse leakage at rated standoff; minimizes standby power loss and signal distortion. |
| TJ max | +175 °C - Maximum junction temperature; enables operation in under-hood automotive or industrial environments. |
| Package | DO-204AC (DO-15) - Industry-standard axial leaded package with tin-plated leads; compatible with through-hole reflow and wave soldering. |
Pinout & Package
DO-204AC (DO-15) package: axial-leaded, molded epoxy case with cathode band marking. Leads are pure tin-plated, solderable per J-STD-002, and meet JESD201 Class 2 whisker resistance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Forward conduction terminal | Connects to lower-potential side (e.g., GND or return path); conducts up to 3.5V forward drop at 35A surge. |
| Cathode | Reverse clamping terminal | Marked with band; connects to protected line (e.g., 78V rail); initiates avalanche clamping when voltage 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. |
| Clamping ratio VC/VBR | ~1.35–1.61 - Low ratio ensures tight voltage limiting relative to breakdown, reducing overvoltage margin risk. |
| Response time | <1.0 ps - Enables suppression of nanosecond-scale ESD and EFT events before sensitive circuitry reacts. |
| RoHS & halogen-free | Complies with IEC 61249-2-21; supports environmentally regulated industrial and automotive supply chains. |
| UL 94V-0 molding | Flame-retardant encapsulation prevents fire propagation in fault conditions per safety-critical designs. |
Applications
| Automotive Power Rail Protection | Industrial Sensor Interface Protection |
|---|---|
Use Scenario: 78V battery-supplied subsystems (e.g., ADAS camera modules, radar ECUs) exposed to load dump and ISO 7637-2 pulses. IC Role / Device Role / Timing Role: Unidirectional TVS placed between 78V input and ground to clamp transients before they reach LDOs or PMICs. Use Value: Limits peak voltage to ≤139V during 500W surges, preventing damage to 80V-rated input capacitors and regulators. | Use Scenario: Analog sensor outputs (e.g., pressure, temperature) routed across noisy factory floors with inductive switching noise. IC Role / Device Role / Timing Role: TVS mounted at connector entry point to shunt fast transients (<1ns rise) before reaching precision ADC front-end. Use Value: Sub-1μA leakage preserves microvolt-level signal integrity; <1.0ps response captures ESD before amplifier saturation. |
| LED Driver Overvoltage Clamp | Telecom DC Power Input Protection |
Use Scenario: Constant-current LED drivers powered from 72–84V DC supplies subject to switching spikes and lightning-induced surges. IC Role / Device Role / Timing Role: Standoff-clamp TVS across input terminals to absorb repetitive 10/1000μs transients without degradation. Use Value: 500W rating handles multiple surge events; 175°C TJ max supports enclosed, thermally constrained lamp housings. | Use Scenario: Central office power feeds (–48V or +78V systems) entering telecom equipment cabinets with long cable runs. IC Role / Device Role / Timing Role: Primary protection stage upstream of DC-DC converters and hot-swap controllers. Use Value: 139V clamping ensures downstream 100V-rated MOSFETs and controllers remain within SOA during lightning-induced surges. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient voltage suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| Littelfuse SMAJ78A | Same DO-214AC package; 78V VWM, 86.7–103V VBR, 139V VC @ 3.7A - identical electrical specs but not AEC-Q101 qualified. | Not validated for automotive use; suitable for industrial/commercial only. | Select if AEC-Q101 is not required and SMA footprint is preferred. |
| ON Semiconductor 1.5KE78A | Higher PPK (1500W), larger DO-201AD package, 78V VWM, 86.7–103V VBR, 139V VC - same clamping but higher surge capacity and thermal mass. | Requires PCB layout change; better for high-energy, infrequent surges (e.g., AC mains coupling). | Select when 1500W surge headroom is needed and board space allows larger package. |
Compared with SMAJ78A and 1.5KE78A, SA78 offers AEC-Q101 qualification in the compact DO-15 form factor, making it optimal for space-constrained automotive modules where 500W surge immunity and full automotive reliability are mandatory.
Availability
SA78 is available at Aetrix Electronics and suitable for automotive power rail protection, industrial sensor interface hardening, and LED driver overvoltage clamping requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for SA78 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, MOSFETs, and bipolar transistors.
The SA Series was designed specifically for robust, high-energy transient suppression in automotive and industrial power systems, emphasizing AEC-Q101 compliance, tight VBR tolerance, and stable clamping performance across temperature.
FAQ
What is the maximum clamping voltage of the SA78 under standard 10/1000μs surge conditions?
The SA78 has a maximum clamping voltage (VC) of 139 V at 3.7 A peak pulse current under the 10/1000μs waveform. This value is measured per ANSI/IEEE C62.35 and guarantees that protected circuits experience no more than 139 V during standardized surge events, preserving the safe operating area of downstream components like regulators and microcontrollers.
Is the SA78 unidirectional or bidirectional, and how is polarity marked?
The SA78 is a unidirectional TVS diode. Polarity is marked by a cathode band on the DO-204AC (DO-15) package body - the banded end connects to the protected line (e.g., 78V rail), while the unbanded end connects to ground. This configuration enables forward conduction only above ~3.5 V and reverse clamping above VBR.
Does the SA78 meet automotive qualification standards?
Yes, the SA78 is AEC-Q101 qualified when ordered with the "H" suffix (e.g., SA78H). The base SA78 part is manufactured to the same process and design as the qualified version, but formal AEC-Q101 certification applies only to parts explicitly marked and tested per the standard - verify ordering code and packaging documentation for qualification status.
What is the junction temperature range and thermal derating behavior of the SA78?
The SA78 operates across a junction temperature range of –55°C to +175°C. Its peak pulse power (500W) is rated at TA = 25°C and derates linearly above that temperature per Figure 2 in the datasheet, reaching ~300W at 100°C ambient. Steady-state power dissipation is 3W at TL = 75°C on 10×10 mm copper pads.
Can the SA78 be used in bidirectional configurations?
No - the SA78 is strictly unidirectional. For bidirectional protection at the same 78V standoff, the SA78A variant must be used. SA78A provides symmetrical clamping in both directions with identical VBR (86.7–95.8 V) and VC (126 V @ 4.1 A), and is marked without polarity banding.
SA78 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:
- 139V
- Current - Peak Pulse (10/1000µs):
- 3.7A
- Power - Peak Pulse:
- 500W
- Power Line Protection:
- No
- Applications:
- General Purpose
- Capacitance @ Frequency:
- -
- Operating Temperature:
- -55°C ~ 175°C (TJ)
- Grade:
- Automotive
- Qualification:
- AEC-Q101
- Mounting Type:
- Through Hole
- Supplier Device Package:
- DO-204AC (DO-15)
SA78 FAQ
1.How can I place an order for SA78 through Aetrix?
Please submit a Request for Quotation (RFQ) for SA78 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 SA78 reliable?
The price and inventory of SA78 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SA78 is usually 5 days.
3.What payment methods are accepted for SA78?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SA78 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SA78?
SA78 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SA78 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 SA78?
For technical support, including SA78 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SA78 requirements.
6.How does Aetrix verify that SA78 is sourced from the original manufacturer or authorized distributors?
All SA78 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 SA78 meets industry standards.
7.What is the process for return or replacement of SA78?
All SA78 units undergo pre-shipment inspection (PSI). If there is an issue with SA78, 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 SA78 part is unused and in its original packaging.
Return procedure for SA78:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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