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onsemi 1SMC78AT3
- Part No.:
- 1SMC78AT3
- Manufacturer:
- onsemi
- Category:
- TVS Diodes
- Package:
- DO-214AB, SMC
- Datasheet:
-
1SMC78AT3.pdf
- Description:
- TVS DIODE 78VWM 126VC SMC
- Quantity:
- Payment:
- Shipping:
Inventory:6,183
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Product details
Overview
1SMC78AT3 from ON Semiconductor is a unidirectional 1500 W transient voltage suppressor (TVS) diode designed for parallel protection of sensitive electronics against ESD, lightning-induced surges, and inductive switching transients. It features a 78 V working peak reverse voltage (VRWM), 91.25 V minimum breakdown voltage (VBR), 126 V maximum clamping voltage (VC) at 11.4 A peak pulse current (IPP), and sub-1 ns response time - deployed in industrial power supplies, automotive ECUs, and medical equipment input stages.
For engineers reviewing the 1SMC78AT3 datasheet, pinout, applications, or equivalent options, key selection criteria include clamping voltage margin vs. protected IC's absolute maximum rating, VRWM alignment with DC bus voltage, thermal derating above 75°C, and UL 497B certification for isolated loop protection compliance.
Technical Context
The 1SMC78AT3 operates as a unidirectional Zener-based TVS diode, conducting only in reverse-biased avalanche mode above its specified VBR. Its clamping action relies on low dynamic impedance and fast carrier injection to limit transient overvoltage within 1 ns of event onset.
It is rated for 1500 W non-repetitive peak pulse power (10/1000 µs waveform), with thermal management defined by 54.6 °C/W junction-to-lead resistance and 165 °C/W junction-to-ambient resistance on FR-4 board. The device meets UL 497B Class 3 ESD rating (>16 kV HBM) and is Pb-free, packaged in ON Semiconductor's Surmetic SMC (Case 403) surface-mount housing.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VRWM | 78 V - Maximum continuous reverse operating voltage before clamping begins; must exceed protected circuit's DC or peak AC voltage. |
| VBR (min) | 91.25 V @ IT = 1 A - Guaranteed avalanche initiation threshold; ensures reliable turn-on without premature conduction. |
| VC (max) | 126 V @ IPP = 11.4 A - Maximum clamped voltage during 10/1000 µs surge; defines worst-case overvoltage seen by downstream components. |
| PPK | 1500 W @ 1 ms - Peak transient energy absorption capacity; determines survivability against lightning or inductive kick events. |
| Response Time | < 1 ns - Time from transient onset to clamping onset; critical for protecting high-speed logic and microcontrollers. |
| IR @ VRWM | 5 µA max - Reverse leakage at rated working voltage; ensures minimal standby power loss and signal integrity in high-impedance nodes. |
| UL Recognition | UL 497B QVGQ2 - Certified for isolated loop circuit protection; validates performance under strike voltage, endurance, and dielectric tests. |
Pinout & Package
1SMC78AT3 is housed in the SMC (Case 403) surface-mount package: 7.75–8.13 mm length × 6.60–7.11 mm width × 1.90–2.41 mm height, with modified L-bend leads for enhanced pad adhesion and cathode polarity indicated by a molded notch.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Forward conduction terminal / low-side reference | Connected to ground or low-voltage rail in unidirectional configuration; establishes reference for clamping threshold. |
| Cathode | Reverse-biased avalanche terminal / high-side connection | Connected to protected line (e.g., 24 V supply rail); conducts when transient exceeds VRWM, shunting surge current to ground. |
Key Features
| Feature | Design Value |
|---|---|
| 1500 W peak pulse power | Enables robust protection against IEC 61000-4-5 Level 4 surges (4 kV line-to-line) without derating in compact SMC footprint. |
| Clamping ratio VC/VBR = 1.38 | Low overvoltage margin ensures protected ICs remain within safe operating area during worst-case transients. |
| UL 497B recognition | Validates suitability for telecom and industrial isolated interfaces where regulatory compliance is mandatory for safety certification. |
| Pb-free Surmetic SMC package | Meets RoHS and J-STD-020 reflow requirements; 260°C soldering tolerance supports automated assembly without delamination risk. |
Applications
| Industrial Power Supply Input Protection | Automotive Body Control Module (BCM) CAN Bus Line Protection |
|---|---|
|
Use Scenario: 24 V DC input stage of programmable logic controller (PLC) power supply exposed to load dump and ISO 7637-2 pulses. IC Role / Device Role / Timing Role: Unidirectional TVS placed between +24 V rail and chassis ground to clamp transients before they reach upstream DC/DC converter ICs. Use Value: 126 V clamping voltage ensures downstream 36 V-rated input capacitors and controllers remain below absolute maximum ratings during 100 V/100 A surge events. |
Use Scenario: CAN_H and CAN_L lines in vehicle BCM subjected to ESD and battery disconnect transients per ISO 10605. IC Role / Device Role / Timing Role: Dual 1SMC78AT3 devices (one per line) provide asymmetric clamping referenced to ground, suppressing common-mode surges while preserving differential signaling integrity. Use Value: Sub-1 ns response prevents >100 V overshoot from reaching CAN transceivers, avoiding latch-up or permanent damage during 15 kV contact discharge. |
| Medical Equipment Isolated Sensor Interface | Telecom DSL Line Card Surge Protection |
|
Use Scenario: 48 V phantom-powered analog sensor interface in patient monitoring device requiring UL 497B-compliant isolation barrier protection. IC Role / Device Role / Timing Role: 1SMC78AT3 installed on primary side of isolated DC/DC converter, clamping surges induced across transformer windings. Use Value: UL 497B certification confirms compliance with creepage/clearance and endurance testing required for Class II medical equipment safety approvals. |
Use Scenario: POTS line interface on DSLAM line card exposed to lightning-induced longitudinal surges up to 1 kV. IC Role / Device Role / Timing Role: Paired 1SMC78AT3 devices protect tip/ring conductors in bridge configuration, shunting common-mode energy to ground while maintaining low capacitance (<100 pF) for <2.2 MHz ADSL signal integrity. Use Value: 78 V VRWM matches typical 56 V RMS ringing voltage, preventing false triggering during normal operation while enabling full 1500 W surge handling. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMBJ78A | Same VRWM (78 V) and VC (126 V), but lower PPK = 600 W; SMB package (smaller footprint, higher thermal resistance). | Limited to lower-energy transients (e.g., ESD-only); unsuitable for IEC 61000-4-5 line surges. | Select 1SMC78AT3 when 1500 W surge immunity is required; choose SMBJ78A only for space-constrained, low-energy ESD-only zones. |
| 1.5SMC78A | Identical electrical specs and SMC package, but obsolete marking (no 'G' suffix); may lack current Pb-free process control and UL 497B documentation traceability. | No functional difference in circuit operation, but lacks documented compliance for new medical/industrial certifications. | Prefer 1SMC78AT3 for new designs requiring RoHS compliance, UL 497B file #E210057, and guaranteed Pb-free manufacturing. |
Compared with SMBJ78A and 1.5SMC78A, the 1SMC78AT3 delivers verified 1500 W surge capability in a production-ready Pb-free SMC package with active UL 497B recognition - making it the only choice for certified industrial and medical surge protection where both energy handling and regulatory validation are mandatory.
Availability
1SMC78AT3 is available at Aetrix Electronics and suitable for industrial power supplies, automotive electronic control units, and medical diagnostic equipment requiring stable component supply with full regulatory documentation and long-term lifecycle support.
Supply support for 1SMC78AT3 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
ON Semiconductor is a global semiconductor manufacturer specializing in power management, analog, sensors, and discrete devices for automotive, industrial, and communications markets.
The 1SMC78AT3 belongs to the SMC-series unidirectional TVS family, engineered specifically for high-energy transient suppression in harsh environments where reliability, UL certification, and consistent clamping performance are critical.
FAQ
What is the maximum clamping voltage of the 1SMC78AT3 at its rated peak pulse current?
The 1SMC78AT3 has a maximum clamping voltage (VC) of 126 V at its rated peak pulse current (IPP) of 11.4 A, measured using the standard 10/1000 µs double-exponential surge waveform. This value defines the highest voltage that will appear across protected circuitry during a full-rated transient event, ensuring downstream components remain within their safe operating voltage limits.
Is the 1SMC78AT3 suitable for bidirectional transient protection?
No, the 1SMC78AT3 is strictly a unidirectional TVS diode, designed to clamp only reverse-biased transients on positive-rail applications. It does not provide symmetrical clamping for AC or bipolar signals. For bidirectional protection, a dedicated bidirectional part such as 1SMC78CA must be used - the 1SMC78AT3 datasheet explicitly states "Bidirectional devices will not be available in this series."
Does the 1SMC78AT3 meet UL 497B requirements for isolated loop protection?
Yes, the 1SMC78AT3 carries full UL 497B recognition under file #E210057 in the Protector category, having passed strike voltage breakdown, endurance conditioning, temperature, dielectric withstand, and discharge tests. This certification is explicitly confirmed in the official ON Semiconductor datasheet and applies to the entire 1SMC5.0AT3 series including the 1SMC78AT3.
What is the thermal resistance from junction to lead for the 1SMC78AT3?
The 1SMC78AT3 has a thermal resistance from junction-to-lead (RJL) of 54.6 °C/W, measured at TL = 75°C with zero lead length on an FR-4 board. This parameter governs heat transfer from the silicon die to the PCB copper, directly impacting sustained surge repetition rate and average power handling in thermally constrained layouts.
How does the 1SMC78AT3 differ from the older 1.5SMC78A part?
The 1SMC78AT3 replaces the 1.5SMC78A with identical electrical specifications and SMC package, but adds Pb-free processing ('G' suffix), updated UL 497B documentation traceability, and tighter process controls per ON Semiconductor's current manufacturing standards. While functionally interchangeable in circuit design, the 1SMC78AT3 is required for new designs targeting RoHS compliance and certified medical/industrial approvals.
1SMC78AT3 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Package/Case:
- DO-214AB, SMC
- Series:
- -
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- 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):
- 11.4A
- Power - Peak Pulse:
- 1500W (1.5kW)
- Power Line Protection:
- No
- Applications:
- General Purpose
- Capacitance @ Frequency:
- -
- Operating Temperature:
- -65°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SMC
1SMC78AT3 FAQ
1.How can I place an order for 1SMC78AT3 through Aetrix?
Please submit a Request for Quotation (RFQ) for 1SMC78AT3 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 1SMC78AT3 reliable?
The price and inventory of 1SMC78AT3 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 1SMC78AT3 is usually 5 days.
3.What payment methods are accepted for 1SMC78AT3?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 1SMC78AT3 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 1SMC78AT3?
1SMC78AT3 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 1SMC78AT3 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 1SMC78AT3?
For technical support, including 1SMC78AT3 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 1SMC78AT3 requirements.
6.How does Aetrix verify that 1SMC78AT3 is sourced from the original manufacturer or authorized distributors?
All 1SMC78AT3 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 1SMC78AT3 meets industry standards.
7.What is the process for return or replacement of 1SMC78AT3?
All 1SMC78AT3 units undergo pre-shipment inspection (PSI). If there is an issue with 1SMC78AT3, 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 1SMC78AT3 part is unused and in its original packaging.
Return procedure for 1SMC78AT3:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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