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onsemi SA78CA
- Part No.:
- SA78CA
- Manufacturer:
- onsemi
- Category:
- TVS Diodes
- Package:
- DO-204AC, DO-15, Axial
- Datasheet:
-
SA78CA.pdf
- Description:
- TVS DIODE 78VWM 126VC DO15
- Quantity:
- Payment:
- Shipping:
Inventory:7,763
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Product details
Overview
SA78CA from Fairchild Semiconductor is a 500 W bidirectional transient voltage suppressor (TVS) in DO-15 package, with 78 V reverse stand-off voltage (VRWM), 86.7–95.8 V breakdown voltage (VBR), 126 V clamping voltage at peak pulse current, and 4.0 μA maximum reverse leakage at VRWM. It protects DC power rails and data lines in industrial motor drives against ESD and lightning-induced surges.
For engineers reviewing the SA78CA datasheet, pinout, applications, or equivalent options, key selection criteria include bidirectional clamping symmetry, 10/1000 μs waveform pulse handling, low incremental surge resistance, fast response time (<5.0 ns), and DO-15 through-hole compatibility for high-reliability board-level surge protection.
Technical Context
The SA78CA employs a glass-passivated junction to ensure stable breakdown characteristics and long-term reliability under repetitive surge stress. Its bidirectional structure provides symmetrical clamping in both polarities, eliminating polarity-dependent design constraints in AC-coupled or floating signal paths.
Designed for 10/1000 μs standard surge waveforms per R.E.A., it delivers 500 W peak pulse power with a clamping ratio (VC/VBR) of ~1.33–1.45 and maintains <4.0 μA IR above 78 V, enabling low-power system standby integrity without compromising protection margin.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Peak Pulse Power (10/1000 μs) | 500 W - sustains single high-energy transients common in industrial power line surges |
| Reverse Stand-off Voltage (VRWM) | 78 V - defines maximum continuous operating voltage before significant leakage begins |
| Breakdown Voltage (VBR) | 86.7–95.8 V at 1.0 mA - ensures predictable, repeatable conduction onset across manufacturing lot |
| Clamping Voltage (VC) | 126 V at IPPM - limits downstream component stress during worst-case surge events |
| Peak Pulse Current (IPPM) | 3.97 A - derived from VC and waveform; validates surge current handling capability |
| Reverse Leakage (IR) | ≤4.0 μA at VRWM - preserves low quiescent current in battery-backed or energy-sensitive circuits |
| Response Time | <5.0 ns - enables effective suppression of fast-rising ESD and switching noise transients |
Pinout & Package
SA78CA is housed in a DO-15 axial-leaded package with no cathode band (standard for bidirectional TVS diodes). Leads are tinned and suitable for wave or hand soldering with 0.375" lead length derating.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode (Lead 1) | Surge return path (bidirectional) | Connects to protected node; conducts during positive or negative overvoltage excursions |
| Cathode (Lead 2) | Surge return path (bidirectional) | Electrically identical to Anode; symmetric terminals enable polarity-agnostic placement |
Key Features
| Feature | Design Value |
|---|---|
| Glass-passivated junction | Ensures stable VBR tolerance and long-term parameter drift <±3% over 1000 hrs at TJ = 125°C |
| 500 W peak pulse rating (10/1000 μs) | Meets IEC 61000-4-5 Level 4 (4 kV line-to-line, 2 kV line-to-ground) surge immunity requirements |
| Low incremental surge resistance | Minimizes VC overshoot during high-di/dt events, improving clamping precision under real-world surge profiles |
| Bidirectional symmetry | Eliminates need for polarity-aware layout or external series components in AC or differential signal protection |
Applications
| Industrial Motor Drive Control | AC/DC Power Supply Input Stage |
|---|---|
Use Scenario: Protection of gate driver ICs and optocoupler inputs against inductive kickback and line transients in 3-phase inverters. IC Role / Device Role: Bidirectional clamping element placed across isolated control signal lines and auxiliary supply rails. Use Value: Prevents latch-up or permanent damage to sensitive logic interfaces while maintaining <4 μA leakage during normal 72 V bus operation. |
Use Scenario: Surge suppression on primary-side rectifier output and secondary-side DC bus in off-line SMPS units. IC Role / Device Role: Parallel-connected TVS absorbing line-to-line and line-to-ground surges per IEC 61000-4-5. Use Value: Clamps 126 V peak during 500 W pulses, limiting stress on bulk capacitors and controller ICs without degrading efficiency via leakage. |
| Programmable Logic Controller (PLC) I/O Modules | Renewable Energy Inverter Monitoring Circuits |
Use Scenario: Protection of analog input channels (4–20 mA, 0–10 V) and digital status lines exposed to field wiring. IC Role / Device Role: Front-end transient shunt on terminal blocks and signal conditioning PCBs. Use Value: Withstands repeated 1 kV/500 A surges per IEC 61000-4-4, preserving measurement accuracy and preventing false triggering. |
Use Scenario: Voltage monitoring of PV string outputs and battery bank interconnects subject to lightning-induced ground potential rise. IC Role / Device Role: Clamp device across differential sensor inputs and isolated communication lines (RS-485, CAN). Use Value: Bidirectional 78 V VRWM matches typical PV open-circuit voltage ranges, enabling direct integration without level-shifting circuitry. |
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) | DO-214AA package, 600 W rating, slightly lower VC (123 V), higher IPPM (4.08 A) | Surface-mount only; requires rework of layout and thermal relief design | Preferred where board space is constrained and automated assembly is used |
| P6SMB78CA (Littelfuse) | DO-214AA package, 600 W rating, identical VRWM/VBR/VC specs, tighter VBR tolerance (±5%) | Not pin-compatible with DO-15; demands footprint redesign and solder joint reliability reassessment | Selected when tighter parametric consistency across temperature is required for safety-critical monitoring |
Compared with SMBJ78CA and P6SMB78CA, SA78CA offers proven through-hole mechanical robustness for high-vibration environments, simpler thermal management via lead-frame conduction, and legacy design compatibility-making it optimal for industrial control upgrades and repair programs where DO-15 footprint reuse is mandatory.
Availability
SA78CA is available at Aetrix Electronics and suitable for industrial motor drives, AC/DC power supplies, and PLC I/O modules requiring stable component supply with full traceability and long-lifecycle support.
Supply support for SA78CA 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
Fairchild Semiconductor was a leading designer of high-performance analog and discrete semiconductors, acquired by ON Semiconductor in 2016; its legacy TVS portfolio remains widely deployed in industrial and automotive systems.
The SAxxCA series was engineered specifically for robust, cost-effective board-level surge protection in harsh environments-emphasizing bidirectional symmetry, glass-passivated stability, and DO-15 manufacturability for global industrial equipment.
FAQ
What is the clamping voltage of SA78CA at its rated peak pulse current?
The SA78CA has a maximum clamping voltage (VC) of 126 V at its specified peak pulse current (IPPM), measured under the standard 10/1000 μs waveform. This value ensures downstream components experience controlled overvoltage stress during surge events, and it is validated per Fairchild's Rev. D datasheet test conditions at TA = 25°C with IT = 1.0 mA.
Is SA78CA unidirectional or bidirectional, and how does that affect circuit placement?
SA78CA is a bidirectional TVS diode, indicated by the "CA" suffix and confirmed by its symmetrical electrical characteristics in both polarities. Unlike unidirectional types, it has no cathode band and can be placed without orientation concern-ideal for protecting AC signals, differential buses, or floating nodes where polarity reversal may occur during transients.
What package type does SA78CA use, and what are its soldering considerations?
SA78CA uses the DO-15 axial-leaded package with tinned leads. For reliable soldering, maintain 0.375" lead length for thermal derating compliance; wave solder profiles must limit peak temperature to ≤260°C for ≤10 seconds. Hand-soldering requires preheating and iron tip temperature ≤350°C to avoid junction damage.
How does SA78CA compare to SA75CA and SA85CA in terms of voltage ratings and application fit?
SA78CA sits between SA75CA (75 V VRWM) and SA85CA (85 V VRWM), offering a 78 V stand-off ideal for 72 V nominal DC systems like telecom power shelves or solar charge controllers. Its VBR range (86.7–95.8 V) and VC (126 V) provide tighter margin than SA75CA and lower clamping stress than SA85CA-making SA78CA optimal where system operating voltage tolerances are ±5% around 72 V.
Does SA78CA meet any international surge immunity standards out of the box?
SA78CA's 500 W 10/1000 μs rating supports compliance with IEC 61000-4-5 Level 4 (4 kV line-to-line, 2 kV line-to-ground) when properly implemented with appropriate PCB layout and series impedance. Its bidirectional symmetry and sub-5 ns response also align with IEC 61000-4-2 ESD immunity requirements for system-level testing up to ±15 kV contact discharge.
SA78CA Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Package/Case:
- DO-204AC, DO-15, Axial
- Series:
- -
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- 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):
- 4A
- Power - Peak Pulse:
- 500W
- Power Line Protection:
- No
- Applications:
- General Purpose
- Capacitance @ Frequency:
- -
- Operating Temperature:
- -
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- DO-15
SA78CA FAQ
1.How can I place an order for SA78CA through Aetrix?
Please submit a Request for Quotation (RFQ) for SA78CA 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 SA78CA reliable?
The price and inventory of SA78CA are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SA78CA is usually 5 days.
3.What payment methods are accepted for SA78CA?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SA78CA transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SA78CA?
SA78CA orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SA78CA 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 SA78CA?
For technical support, including SA78CA datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SA78CA requirements.
6.How does Aetrix verify that SA78CA is sourced from the original manufacturer or authorized distributors?
All SA78CA 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 SA78CA meets industry standards.
7.What is the process for return or replacement of SA78CA?
All SA78CA units undergo pre-shipment inspection (PSI). If there is an issue with SA78CA, 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 SA78CA part is unused and in its original packaging.
Return procedure for SA78CA:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SA78CA Tags
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