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Vishay General Semiconductor - Diodes Division SMAJ78CAHM3/I
- Part No.:
- SMAJ78CAHM3/I
- Manufacturer:
- Vishay General Semiconductor - Diodes Division
- Category:
- TVS Diodes
- Package:
- DO-214AC, SMA
- Datasheet:
-
SMAJ78CAHM3/I.pdf
- Description:
- TVS DIODE 78VWM 126VC DO214AC
- Quantity:
- Payment:
- Shipping:
Inventory:8,299
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Product details
Overview
SMAJ78CAHM3/I from Vishay General Semiconductor is a bidirectional transient voltage suppressor (TVS) diode in SMA (DO-214AC) package, designed for clamping voltage transients on power and signal lines. It features a 78 V stand-off voltage (VWM), 86.7–95.8 V breakdown voltage (VBR) at 1 mA, 126 V maximum clamping voltage (VC) at 3.2 A peak pulse current, and 400 W peak pulse power rating with 10/1000 μs waveform.
For engineers reviewing the SMAJ78CAHM3/I datasheet, SMAJ78CAHM3/I pinout, SMAJ78CAHM3/I application, or SMAJ78CAHM3/I equivalent, key selection criteria include bidirectional surge protection capability, AEC-Q101 qualification for automotive use, halogen-free RoHS compliance (HM3 suffix), and compatibility with automated SMT placement on PCBs with 0.2" × 0.2" copper pads.
Technical Context
This TVS diode operates symmetrically in both directions due to its bidirectional construction, enabling protection of AC-coupled or floating signal paths without polarity concerns. Its glass-passivated junction ensures stable breakdown characteristics and low leakage (<1.0 μA at 78 V), while the low incremental surge resistance supports effective energy diversion during ESD or lightning-induced transients.
The device is rated for repetitive 10/1000 μs surges at 0.01% duty cycle (400 W up to 78 V; derated to 300 W above 78 V), with thermal resistance of 120 °C/W (junction-to-ambient) and 30 °C/W (junction-to-lead), requiring appropriate PCB copper area for sustained power dissipation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VWM | 78 V - Maximum continuous reverse operating voltage before clamping begins |
| VBR min/max | 86.7 V / 95.8 V at 1 mA - Confirmed breakdown threshold range under standardized test conditions |
| VC @ IPPM | 126 V at 3.2 A - Clamped voltage during 10/1000 μs surge, defining worst-case overvoltage seen by protected circuit |
| PPPM | 400 W - Peak pulse power handling capacity with 10/1000 μs waveform, critical for IEC 61000-4-5 compliance margin |
| IFSM | 40 A - Non-repetitive forward surge current rating (8.3 ms half-sine), relevant for unidirectional fault analysis |
| TJ max | +150 °C - Maximum junction temperature, constraining thermal design in high-ambient environments |
| Package | SMA (DO-214AC) - Surface-mount outline with 5.28 mm length, 4.50 mm width, and 2.29 mm height for compact board layout |
Pinout & Package
Package: SMA (DO-214AC), molded plastic case with matte tin-plated leads, MSL Level 1 compliant (reflow peak 260 °C), UL 94 V-0 rated.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Current entry point in forward bias | Terminal where conventional current flows into device during forward conduction; not marked on bidirectional types |
| Cathode | Current exit point in forward bias | Terminal where conventional current exits device during forward conduction; no band marking on bidirectional SMAJ78CAHM3/I |
Key Features
| Feature | Design Value |
|---|---|
| Bidirectional clamping | Enables symmetrical transient suppression on AC or floating lines without polarity constraints |
| AEC-Q101 qualified | Validated for automotive-grade reliability including temperature cycling, HTRB, and ESD testing per JESD22 |
| Halogen-free & RoHS-compliant (HM3) | Meets environmental compliance requirements for automotive and industrial end equipment |
| 400 W peak pulse power (≤78 V) | Supports robust protection against IEC 61000-4-5 Level 4 surges (4 kV line-earth, 2 kV line-line) |
| Low clamping ratio (VC/VBR ≈ 1.31) | Minimizes overvoltage stress on downstream ICs compared to higher-ratio TVS devices |
Applications
| Automotive Power Line Protection | Industrial Sensor Interface Protection |
|---|---|
Use Scenario: Protecting 12 V battery-fed ECUs from load dump and alternator transients. IC Role / Device Role / Timing Role: Bidirectional TVS placed across power rail to clamp spikes up to ±120 V. Use Value: Prevents latch-up or permanent damage to microcontrollers and CAN transceivers during ISO 7637-2 Pulse 5a events. | Use Scenario: Shielding analog sensor outputs (e.g., pressure, temperature) from ESD and cable discharge events. IC Role / Device Role / Timing Role: Low-capacitance TVS connected between signal line and ground to divert fast transients. Use Value: Maintains signal integrity below 100 pF capacitance while suppressing ±8 kV contact ESD per IEC 61000-4-2. |
| Telecom DC Power Input Protection | Consumer USB Port Surge Suppression |
Use Scenario: Safeguarding PoE-powered network switches against induced surges on 48 V DC input rails. IC Role / Device Role / Timing Role: Bidirectional TVS installed between +48 V and return to limit overvoltage during lightning-induced surges. Use Value: Withstands 300 W surge power above 78 V and maintains clamping below 126 V to protect DC-DC converters. | Use Scenario: Adding secondary-level surge immunity to USB Type-A/B ports in set-top boxes or docking stations. IC Role / Device Role / Timing Role: TVS placed on VBUS line to absorb hot-plug transients and nearby ESD events. Use Value: Fast response time (<1 ns) and low leakage (<1 μA) prevent interference with USB enumeration and data integrity. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient voltage suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMAJ78CAHE3/I | Same electrical specs; RoHS-compliant but not halogen-free (E3 vs HM3) | Acceptable for commercial/industrial use where halogen-free requirement is absent | Select when AEC-Q101 qualification is required but halogen-free material is optional |
| SMBJ78CAHM3/I | Same VWM, VBR, VC; higher PPPM = 600 W (SMB package, larger footprint) | Better suited for higher-energy surge environments where PCB space allows larger package | Choose when system-level surge testing exceeds 400 W and SMB's 150 °C/W RθJA is acceptable |
Compared with SMAJ78CAHE3/I, the SMAJ78CAHM3/I adds halogen-free compliance without sacrificing AEC-Q101 qualification; versus SMBJ78CAHM3/I, it trades 200 W lower pulse power for 30% smaller PCB area and identical thermal performance per unit volume.
Availability
SMAJ78CAHM3/I is available at Aetrix Electronics and suitable for automotive electronics, industrial sensor interfaces, telecom power inputs, and consumer USB port protection requiring stable component supply and long-term lifecycle support.
Supply support for SMAJ78CAHM3/I 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
Vishay General Semiconductor is a global leader in discrete semiconductors, specializing in diodes, rectifiers, MOSFETs, and protection devices with emphasis on reliability and application-specific optimization.
The SMAJ series is engineered for surface-mount transient suppression in automotive, industrial, and communications systems where bidirectional clamping, AEC-Q101 validation, and compact packaging are essential.
FAQ
What does the 'HM3' suffix indicate in SMAJ78CAHM3/I?
The 'HM3' suffix denotes halogen-free, RoHS-compliant construction with AEC-Q101 qualification. It confirms the device meets automotive reliability standards while using environmentally restricted materials-critical for Tier 1 automotive suppliers and industrial OEMs with strict material declarations. The SMAJ78CAHM3/I is tested per JESD22 and qualified for temperature cycling, highly accelerated life testing, and ESD robustness.
Is SMAJ78CAHM3/I suitable for protecting CAN bus lines?
Yes, SMAJ78CAHM3/I is appropriate for CAN bus protection when placed across the differential pair (CAN_H/CAN_L) or from each line to ground. Its bidirectional operation handles common-mode transients, and its 126 V clamping voltage provides margin above typical CAN fault voltages (±40 V). However, ensure layout minimizes parasitic inductance and verify total capacitance (typically <100 pF) does not degrade bit-rate timing in high-speed CAN FD designs.
How does the 10/1000 μs waveform rating apply to real-world surge events?
The 400 W rating for SMAJ78CAHM3/I is defined under the standardized 10/1000 μs double-exponential surge waveform per IEC 61000-4-5, modeling lightning-induced surges on AC mains or long cables. In practice, this means the SMAJ78CAHM3/I can safely clamp a 3.2 A peak current event lasting ~1000 μs without degradation-validating its use in Level 3–4 surge immunity testing for industrial and automotive equipment.
Does SMAJ78CAHM3/I have polarity markings on the package?
No, SMAJ78CAHM3/I has no cathode band or polarity marking because it is a bidirectional TVS diode. Unlike unidirectional variants (e.g., SMAJ78A), the CA version functions identically in both directions, eliminating the need for orientation during placement. This simplifies automated assembly and reduces risk of misorientation errors in high-volume SMT production.
What is the maximum PCB copper pad size recommended for SMAJ78CAHM3/I to achieve full 400 W rating?
To achieve the full 400 W peak pulse power rating, Vishay specifies mounting SMAJ78CAHM3/I on 0.2" × 0.2" (5.0 mm × 5.0 mm) copper pads per terminal. Smaller pads reduce heat dissipation and cause derating-e.g., a 0.1" × 0.1" pad may limit sustainable pulse power to ~250 W. Thermal simulation or empirical testing is recommended when using non-standard layouts, especially in high-temperature ambient environments.
SMAJ78CAHM3/I Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Vishay General Semiconductor - Diodes Division
- Package/Case:
- DO-214AC, SMA
- Series:
- TransZorb®
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Discontinued at Digi-Key
- 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):
- 3.2A
- Power - Peak Pulse:
- 400W
- Power Line Protection:
- No
- Applications:
- Telecom
- Capacitance @ Frequency:
- -
- Operating Temperature:
- -55°C ~ 150°C (TJ)
- Grade:
- Automotive
- Qualification:
- AEC-Q101
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- DO-214AC (SMA)
SMAJ78CAHM3/I FAQ
1.How can I place an order for SMAJ78CAHM3/I through Aetrix?
Please submit a Request for Quotation (RFQ) for SMAJ78CAHM3/I 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 SMAJ78CAHM3/I reliable?
The price and inventory of SMAJ78CAHM3/I are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMAJ78CAHM3/I is usually 5 days.
3.What payment methods are accepted for SMAJ78CAHM3/I?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMAJ78CAHM3/I transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMAJ78CAHM3/I?
SMAJ78CAHM3/I orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMAJ78CAHM3/I 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 SMAJ78CAHM3/I?
For technical support, including SMAJ78CAHM3/I datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMAJ78CAHM3/I requirements.
6.How does Aetrix verify that SMAJ78CAHM3/I is sourced from the original manufacturer or authorized distributors?
All SMAJ78CAHM3/I 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 SMAJ78CAHM3/I meets industry standards.
7.What is the process for return or replacement of SMAJ78CAHM3/I?
All SMAJ78CAHM3/I units undergo pre-shipment inspection (PSI). If there is an issue with SMAJ78CAHM3/I, 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 SMAJ78CAHM3/I part is unused and in its original packaging.
Return procedure for SMAJ78CAHM3/I:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SMAJ78CAHM3/I Tags
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