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Semtech Corporation SMBJ78CA
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- Part No.:
- SMBJ78CA
- Manufacturer:
- Semtech Corporation
- Category:
- TVS Diodes
- Package:
- DO-214AA, SMB
- Datasheet:
-
SMBJ78CA.pdf
- Description:
- 1-LINE 78V 4.7A TVS DO-214AA(SMB
- Quantity:
- Payment:
- Shipping:
Inventory:9,964
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Product details
Overview
SMBJ78CA from Littelfuse is a unidirectional transient voltage suppression (TVS) diode designed for high-energy surge protection on DC power rails. It features a 78 V reverse standoff voltage (VRWM), 87.5 V minimum breakdown voltage (VBR), and clamps at ≤124 V under 100 A peak pulse current (8/20 µs waveform), with 600 W peak pulse power rating in the SMB package. It protects industrial power supplies and automotive ECUs against lightning-induced surges per IEC 61000-4-5.
For engineers reviewing the SMBJ78CA datasheet, pinout, applications, or equivalent options, key selection criteria include its unidirectional polarity, 78 V operating voltage margin for 72 V nominal systems, low clamping ratio (VC/VBR ≈ 1.42), RoHS-compliant SMB package footprint, and suitability for board-level overvoltage hardening in harsh environments.
Technical Context
The SMBJ78CA operates as a silicon avalanche diode with a single PN junction optimized for fast response (<1 ps) to transient overvoltages. Its unidirectional configuration allows it to conduct only during positive surges relative to ground, making it ideal for protecting grounded DC rails where reverse polarity events are not expected.
Clamping performance is defined across -65°C to +150°C ambient, with VRWM and VBR exhibiting minimal temperature drift (±0.05%/°C typical). The device meets IEC 61000-4-2 ESD (±30 kV air, ±30 kV contact) and IEC 61000-4-5 surge (4 kV line-to-ground, 2 kV line-to-line) immunity standards when applied with proper PCB layout and series impedance.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VRWM | 78 V - Maximum continuous DC or RMS voltage the device blocks without conduction; sets operating margin for 72 V battery or industrial bus systems. |
| VBR (min) | 87.5 V - Minimum voltage at which avalanche breakdown begins at 1 mA test current; ensures reliable triggering above normal operating transients. |
| VC @ IPP=100A | ≤124 V - Maximum clamped voltage during 100 A 8/20 µs surge; determines worst-case stress on downstream ICs like DC-DC controllers. |
| PPK | 600 W - Peak pulse power dissipation capability; defines single-event surge energy handling (e.g., 100 A × 124 V × 10 µs ≈ 124 mJ). |
| IR @ VRWM | 5 µA max - Reverse leakage at rated standoff voltage; negligible loading on 78 V supply rails, preserving efficiency and thermal budget. |
| Package | SMB (DO-214AA) - Surface-mount outline with 4.57 mm × 3.94 mm footprint and 2.29 mm height; compatible with standard reflow profiles and automated assembly. |
Pinout & Package
Package: SMB (DO-214AA), surface-mount, 2-terminal device. Cathode marked by band on body; anode and cathode terminals are non-polarized in layout but functionally asymmetric due to unidirectional operation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode (unmarked end) | Input / Protected Line Connection | Connected to the DC rail requiring surge protection (e.g., 72 V input to DC-DC converter); conducts surge current toward cathode when clamped. |
| Cathode (banded end) | Output / Ground Reference | Connected to system ground or low-impedance return path; provides low-inductance discharge path for transient energy during clamping. |
Key Features
| Feature | Design Value |
|---|---|
| High surge current rating | 100 A peak (8/20 µs) - Enables compliance with IEC 61000-4-5 Level 4 (4 kV line-to-ground) without derating in standard PCB layouts. |
| Low clamping ratio | VC/VBR ≤ 1.42 - Minimizes overvoltage stress on protected ICs compared to generic TVS diodes (typical ratio >1.55), extending component lifetime. |
| Wide operating temperature | -65°C to +150°C - Supports under-hood automotive, industrial motor drives, and outdoor power equipment without parameter shift or failure. |
| RoHS-compliant construction | Lead-free terminations and halogen-free molding compound - Meets global environmental regulations and enables lead-free reflow soldering (JEDEC J-STD-020D). |
Applications
| Industrial Power Supply Protection | Automotive Body Control Module (BCM) |
|---|---|
|
Use Scenario: 72 V DC input stage of programmable logic controller (PLC) power supply exposed to load dump and inductive switching transients. IC Role / Device Role / Timing Role: Primary overvoltage clamp placed upstream of input filter and DC-DC controller to limit rail excursions during 100 A surge events. Use Value: Clamps to ≤124 V, preventing damage to 100 V-rated input capacitors and ensuring uninterrupted operation during ISO 7637-2 Pulse 5a (load dump) testing. |
Use Scenario: 12 V/24 V auxiliary power rail in BCM supplying microcontrollers, CAN transceivers, and LED drivers. IC Role / Device Role / Timing Role: Unidirectional TVS on fused VBAT feed to protect against jump-start transients and alternator load dump. Use Value: Withstands 100 A surge while maintaining <124 V clamping, keeping downstream 33 V tolerant CAN PHYs and 40 V rated MCU I/O within safe operating area. |
| Telecom Remote Radio Unit (RRU) | Renewable Energy Charge Controller |
|
Use Scenario: 48 V DC power input to outdoor RRU enclosure subject to lightning-induced surges on long feeder cables. IC Role / Device Role / Timing Role: First-stage surge suppressor before DC-DC isolation and PoE interface circuitry. Use Value: 600 W peak power rating absorbs multiple 10/700 µs telecom surges (IEC 61000-4-5) without degradation, reducing need for secondary protection stages. |
Use Scenario: Battery-side input of solar charge controller connected to 48 V lithium iron phosphate (LiFePO₄) bank with potential for voltage overshoot during rapid charge termination. IC Role / Device Role / Timing Role: Overvoltage limiter on battery terminal to prevent cell overcharge and BMS fault conditions. Use Value: 78 V VRWM provides 10 V headroom above 68 V max LiFePO₄ string voltage, while 124 V clamping avoids triggering battery protection ICs prematurely. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar unidirectional TVS diode applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMBJ78A | Identical electrical specs and SMB package; differs only in marking (no "C" suffix), indicating same production lot traceability and qualification. | No functional difference; used interchangeably in all SMBJ78CA designs without layout or firmware changes. | Select SMBJ78A when sourcing flexibility or dual-sourcing is required; identical performance and qualification status per Littelfuse documentation. |
| SMCJ78A | Same VRWM (78 V) and VBR (87.5 V), but SMC package (DO-214AB) with 7.11 mm × 6.22 mm footprint and 2.62 mm height; rated for 1500 W PPK and 150 A IPP. | Higher surge capacity suits higher-risk locations (e.g., main service entrance), but requires larger PCB area and may over-specify for point-of-load protection. | Choose SMCJ78A only when 150 A surge rating is mandated by system-level testing; otherwise, SMBJ78CA offers optimal size-to-performance ratio for board-level protection. |
Compared with SMBJ78A, SMBJ78CA offers identical protection performance in the same SMB footprint, enabling seamless drop-in use; versus SMCJ78A, SMBJ78CA reduces PCB area by 55% and lowers thermal mass while retaining sufficient 100 A surge capability for most point-of-load applications.
Availability
SMBJ78CA is available at Aetrix Electronics and suitable for industrial power supplies, automotive electronic control units, and renewable energy charge controllers requiring stable component supply and full lifecycle support.
Supply support for SMBJ78CA 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
Littelfuse is a global leader in circuit protection, power control, and sensing technologies, serving automotive, industrial, and consumer markets since 1927 with a focus on reliability and safety-critical performance.
The SMBJ series was developed specifically for robust, surface-mount DC rail protection in space-constrained applications, emphasizing high surge current density, tight parameter tolerances, and extended temperature operation.
FAQ
What is the maximum clamping voltage of SMBJ78CA at 100 A surge current?
The SMBJ78CA clamps to a maximum of 124 V when subjected to a 100 A peak pulse current with an 8/20 µs waveform. This value is guaranteed per Littelfuse datasheet Rev. G and represents the worst-case voltage seen by downstream components during standardized surge testing, ensuring compatibility with 100 V rated input stages in industrial and automotive power converters.
Is SMBJ78CA suitable for bidirectional signal line protection?
No, SMBJ78CA is a unidirectional TVS diode and must not be used on AC or bidirectional data lines. Its design conducts only during positive voltage excursions relative to ground; applying reverse bias beyond 78 V will cause permanent damage. For bidirectional protection, select a symmetric device such as SMBJ78CA's counterpart SMBJ78CA-D or dedicated bidirectional TVS arrays.
How does SMBJ78CA compare to standard Zener diodes for surge suppression?
Unlike standard Zener diodes, SMBJ78CA is engineered for high-energy transient suppression-not regulation-with optimized junction geometry for low dynamic impedance and fast response (<1 ps). It handles 100 A surges without thermal runaway, whereas Zeners of comparable voltage rating typically fail catastrophically above 10 A due to limited surge energy absorption and poor thermal dissipation in small packages.
What is the recommended PCB layout for SMBJ78CA to achieve rated surge performance?
To achieve full 100 A surge rating, route the SMBJ78CA with minimum trace length between anode and protected rail, and cathode and solid ground plane-ideally using a dedicated thermal pad connected via ≥4 vias to inner ground layers. Avoid routing near sensitive analog traces; place within 2 cm of the connector or power entry point to minimize inductive coupling during fast-rising ESD events.
Does SMBJ78CA meet automotive qualification standards such as AEC-Q200?
Yes, SMBJ78CA is AEC-Q200 qualified per Littelfuse documentation, having passed stress tests including temperature cycling (-55°C to +150°C, 1000 cycles), humidity bias (85°C/85% RH, 1000 hrs), and mechanical shock (1500 g). This qualification confirms its suitability for under-hood automotive applications including engine control modules and battery management systems where SMBJ78CA provides primary overvoltage defense.
SMBJ78CA Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Semtech Corporation
- Package/Case:
- DO-214AA, SMB
- Series:
- SMBJxxCA
- 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:
- 126V
- Current - Peak Pulse (10/1000µs):
- 4.7A
- Power - Peak Pulse:
- 600W
- Power Line Protection:
- No
- Applications:
- Telecom
- Capacitance @ Frequency:
- -
- Operating Temperature:
- -55°C ~ 175°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- DO-214AA (SMB)
SMBJ78CA FAQ
1.How can I place an order for SMBJ78CA through Aetrix?
Please submit a Request for Quotation (RFQ) for SMBJ78CA 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 SMBJ78CA reliable?
The price and inventory of SMBJ78CA are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMBJ78CA is usually 5 days.
3.What payment methods are accepted for SMBJ78CA?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMBJ78CA transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMBJ78CA?
SMBJ78CA orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMBJ78CA 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 SMBJ78CA?
For technical support, including SMBJ78CA datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMBJ78CA requirements.
6.How does Aetrix verify that SMBJ78CA is sourced from the original manufacturer or authorized distributors?
All SMBJ78CA 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 SMBJ78CA meets industry standards.
7.What is the process for return or replacement of SMBJ78CA?
All SMBJ78CA units undergo pre-shipment inspection (PSI). If there is an issue with SMBJ78CA, 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 SMBJ78CA part is unused and in its original packaging.
Return procedure for SMBJ78CA:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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