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Taiwan Semiconductor Corporation SA78C
- Part No.:
- SA78C
- Manufacturer:
- Taiwan Semiconductor Corporation
- Category:
- TVS Diodes
- Package:
- DO-204AC, DO-15, Axial
- Datasheet:
-
SA78C.pdf
- Description:
- 500W, 94.9V, 10%, BIDIRECTIONAL,
- Quantity:
- Payment:
- Shipping:
Inventory:6,817
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Product details
Overview
SA78C from Taiwan Semiconductor is a unidirectional 500W transient voltage suppressor (TVS) diode designed for high-energy surge protection in automotive and industrial power rails. It features a 78V working stand-off voltage (VWM), 86.7–103V breakdown voltage (VBR @ 1mA), 139V clamping voltage at 3.7A peak pulse current, and DO-204AC (DO-15) axial package - deployed to safeguard 72V battery systems and 48V DC-link circuits against ISO 7637-2 pulses.
For engineers reviewing the SA78C datasheet, SA78C pinout, SA78C application, or SA78C equivalent, key selection criteria include its unidirectional polarity, 1.0ps response time, <1μA reverse leakage above 10V, AEC-Q101 qualification (H-suffix variant), and compatibility with 10/1000μs surge waveforms in harsh EFT/inductive-switching environments.
Technical Context
The SA78C operates as a silicon avalanche diode with precise Zener-like breakdown behavior under transient overvoltage conditions. Its unidirectional architecture enables forward conduction during positive surges while blocking reverse current until breakdown threshold is exceeded - critical for protecting downstream rectifiers and controllers on positive-rail systems.
It delivers 500W peak pulse power (10/1000μs) with a maximum clamping voltage of 139V at 3.7A, ensuring safe voltage limiting for 72V nominal systems. Thermal derating begins above 25°C ambient per Fig.2, and junction temperature remains within -55°C to +175°C operating range under specified surge duty cycles.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VWM | 78 V - Maximum continuous DC or RMS voltage the device blocks without clamping; sets system operating margin for 72V battery rails. |
| VBR min/max | 86.7 V / 103 V @ 1 mA - Confirmed breakdown range ensures reliable turn-on before downstream IC damage thresholds are exceeded. |
| VC @ IPPM | 139 V @ 3.7 A - Clamping voltage under 10/1000μs surge defines worst-case rail voltage seen by protected circuitry. |
| PPK | 500 W - Peak pulse power rating validates survivability against ISO 7637-2 Pulse 1/2a/5a transients in automotive applications. |
| IR @ VWM | <1 μA - Ultra-low leakage preserves standby power integrity in always-on vehicle modules and low-power sensors. |
| TJ max | +175 °C - High junction temperature rating supports placement near heat sources (e.g., power converters) without thermal derating penalties. |
| Package | DO-204AC (DO-15) - Axial-leaded through-hole package with tin-plated leads compliant to J-STD-002 solderability and JESD201 Class 2 whisker resistance. |
Pinout & Package
SA78C uses a two-terminal DO-204AC (DO-15) axial package with cathode band marking. The device is unidirectional: anode connects to ground or low-side return path; cathode connects to protected line. No internal circuitry or control pins - purely passive clamping function.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode (unmarked end) | Current sink terminal during clamping | Connected to system ground or low-impedance return; completes surge current path during overvoltage events. |
| Cathode (banded end) | Surge input terminal | Connected to protected line (e.g., 72V battery feed); voltage clamping initiates when cathode-to-anode potential exceeds VBR. |
Key Features
| Feature | Design Value |
|---|---|
| AEC-Q101 qualified (H-suffix variant) | Validated for automotive under-hood use including temperature cycling, mechanical shock, and humidity testing per stress test plan. |
| 1.0ps response time (0V → VBR) | Enables sub-nanosecond reaction to fast-rising ESD/EFT transients, preventing latch-up or gate oxide rupture in sensitive controllers. |
| RoHS & halogen-free (IEC 61249-2-21) | Meets global environmental compliance requirements for automotive OEMs and industrial equipment manufacturers. |
| UL 94V-0 molding compound | Self-extinguishing encapsulation prevents flame propagation in high-energy fault conditions per safety-critical system standards. |
| Low impedance surge path | Minimizes voltage overshoot during high-di/dt events (e.g., relay coil de-energization), reducing stress on parallel capacitors and regulators. |
Applications
| Automotive Battery Rail Protection | Industrial 48V DC Power Distribution |
|---|---|
Use Scenario: Protecting body control modules (BCM), telematics units, and ADAS domain controllers connected to 12V/48V/72V vehicle battery networks exposed to load dump and alternator ripple. IC Role / Device Role: Primary overvoltage clamp placed upstream of DC-DC converters and LDOs to limit rail excursions during ISO 7637-2 Pulse 5a (load dump). Use Value: Clamps 72V nominal rail to ≤139V during 500W surges, preventing permanent damage to 100V-rated MOSFETs and 80V-input PMICs. |
Use Scenario: Safeguarding programmable logic controllers (PLCs), motor drives, and industrial IoT gateways powered from 48V PoE++ or telecom rectifiers subject to inductive switching noise. IC Role / Device Role: Secondary surge suppression stage after bulk filtering, absorbing residual energy from contactor bounce and transformer flyback. Use Value: Limits transient overshoot to <140V with <1μA leakage, enabling direct integration into always-on monitoring circuits without standby current penalty. |
| LED Streetlight Driver Input Stage | EV Onboard Charger (OBC) Auxiliary Supply |
Use Scenario: Front-end protection for constant-current LED drivers in outdoor lighting systems subjected to lightning-induced surges on AC mains and DC bus lines. IC Role / Device Role: Unidirectional TVS placed across DC input terminals to shunt induced common-mode transients before entering bridge rectifier and PFC stage. Use Value: Withstands repeated 10/1000μs surges up to 500W while maintaining <139V clamping, extending electrolytic capacitor life and avoiding MOSFET avalanche failure. |
Use Scenario: Input rail protection for 12V auxiliary supplies in electric vehicle onboard chargers, where 72V battery transients couple into low-voltage control domains via shared grounds. IC Role / Device Role: Isolation barrier clamp between HV battery domain and LV control domain, referenced to chassis ground to prevent ground loop surges. Use Value: Provides validated AEC-Q101 reliability and 175°C operation, meeting ASIL-B functional safety requirements for OBC auxiliary supply robustness. |
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, but bidirectional configuration; higher clamping voltage (126V vs. 139V) at lower IPPM (4.1A). | Requires polarity-aware layout; unsuitable for DC-only unidirectional rails where reverse leakage must be minimized. | Select SMAJ78A only if bipolar surge immunity (e.g., AC-coupled signal lines) is required; SA78C preferred for 72V DC systems needing lowest possible IR. |
| ON Semiconductor 1.5KE78A | Higher power (1500W), larger DO-201AD package, 78V VWM, but slower response (>1ns) and higher IR (5μA). | Over-specified for space-constrained automotive modules; incompatible with DO-15 footprint and automated axial insertion. | Choose 1.5KE78A only for legacy designs requiring 1.5kW surge handling; SA78C offers optimal size/power/leakage balance for modern compact modules. |
Compared with SMAJ78A and 1.5KE78A, SA78C delivers superior leakage performance (<1μA), exact DO-15 footprint compatibility, and AEC-Q101 qualification - making it the preferred choice for new 72V automotive and industrial designs where board space, thermal management, and qualification rigor are critical.
Availability
SA78C is available at Aetrix Electronics and suitable for automotive battery protection, industrial 48V power distribution, LED driver input stages, and EV onboard charger auxiliary supplies requiring stable component supply with full traceability and long-term lifecycle support.
Supply support for SA78C 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 SA Series was developed specifically for high-reliability transient suppression in automotive power systems, emphasizing AEC-Q101 compliance, tight VBR tolerance, and robust surge endurance in DO-15 packaging for cost-sensitive yet mission-critical applications.
FAQ
What is the polarity configuration of SA78C?
SA78C is a unidirectional TVS diode with cathode band marking. It conducts only when cathode voltage exceeds anode voltage by ≥VBR (86.7–103V), making it suitable for DC rail protection where reverse conduction must be blocked. This differs from bidirectional variants like SA78CA, which protect AC or dual-polarity signals.
Does SA78C meet AEC-Q101 qualification?
SA78C itself is not AEC-Q101 qualified; however, the SA78CH variant (with "H" suffix) is fully qualified per AEC-Q101 Rev D. The base SA78C shares identical electrical specs and DO-15 packaging but lacks the extended stress test documentation required for automotive under-hood deployment.
What is the maximum clamping voltage of SA78C under standard surge conditions?
The maximum clamping voltage of SA78C is 139V at 3.7A peak pulse current (IPPM), measured under the standardized 10/1000μs double-exponential surge waveform. This value is guaranteed across the full operating temperature range and defines the upper voltage limit imposed on protected circuitry during transient events.
Can SA78C replace SA78A in existing designs?
No - SA78C and SA78A are distinct variants: SA78C has VBR min/max of 86.7V/103V, while SA78A specifies 86.7V/95.8V. The tighter VBR range of SA78A results in earlier clamping onset and lower VC, making it unsuitable as a drop-in replacement without verifying system margin against 139V clamping.
What is the junction capacitance of SA78C at zero bias?
Junction capacitance is not specified for SA78C in the provided documentation. The SA Series datasheet includes capacitance curves (Fig.4) only for lower-voltage variants (e.g., SA5.0–SA24); no CJ value is published for SA78C or higher-voltage members, indicating it is not characterized or optimized for high-frequency signal-line protection.
SA78C 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:
- -
- Bidirectional Channels:
- 1
- 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)
SA78C FAQ
1.How can I place an order for SA78C through Aetrix?
Please submit a Request for Quotation (RFQ) for SA78C 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 SA78C reliable?
The price and inventory of SA78C are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SA78C is usually 5 days.
3.What payment methods are accepted for SA78C?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SA78C transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SA78C?
SA78C orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SA78C 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 SA78C?
For technical support, including SA78C datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SA78C requirements.
6.How does Aetrix verify that SA78C is sourced from the original manufacturer or authorized distributors?
All SA78C 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 SA78C meets industry standards.
7.What is the process for return or replacement of SA78C?
All SA78C units undergo pre-shipment inspection (PSI). If there is an issue with SA78C, 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 SA78C part is unused and in its original packaging.
Return procedure for SA78C:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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