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Taiwan Semiconductor Corporation SMAJ78H
- Part No.:
- SMAJ78H
- Manufacturer:
- Taiwan Semiconductor Corporation
- Category:
- TVS Diodes
- Package:
- DO-214AC, SMA
- Datasheet:
-
SMAJ78H.pdf
- Description:
- TVS DIODE 78VWM 139VC DO214AC
- Quantity:
- Payment:
- Shipping:
Inventory:2,188
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Product details
Overview
SMAJ78H from Taiwan Semiconductor is a unidirectional 400W surface-mount transient voltage suppressor (TVS) diode in DO-214AC (SMA) package, with 78V working stand-off voltage (VWM), 86.7–106V breakdown voltage (VBR), and 139V maximum clamping voltage (VC) at 2.9A peak impulse current - designed for automotive-grade overvoltage protection in DC/DC converters and SMPS inputs.
For engineers reviewing the SMAJ78H datasheet, SMAJ78H pinout, SMAJ78H application, or SMAJ78H equivalent, this page delivers verified electrical parameters, AEC-Q101 qualification status, ISO 7637-2 pulse compliance, moisture sensitivity level (MSL 1), and real-world clamping performance under 10/1000μs surge conditions.
Technical Context
The SMAJ78H operates as a unidirectional avalanche diode with glass-passivated junction, optimized for fast response (<1.0ps rise from 0 V to VBR min) and low leakage (<1μA at VWM). Its single-die DO-214AC construction supports automated placement and meets JESD201 Class 2 whisker resistance.
It delivers 400W peak pulse power at TA = 25°C per 10/1000μs waveform (derated above ambient), with steady-state power dissipation of 1W and operating junction temperature range from –55°C to +150°C - validated for harsh-environment automotive and industrial applications.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VWM | 78 V - Maximum continuous reverse operating voltage before clamping begins |
| VBR @ IT=1mA | 86.7–106 V - Breakdown voltage range defining reliable avalanche initiation threshold |
| VC @ IPPM=2.9A | 139 V - Clamped voltage during 10/1000μs surge, limiting downstream circuit stress |
| PPPM | 400 W - Peak pulse power handling capability at 25°C, critical for ISO 7637-2 Pulse 1/2a/2b/3a/3b immunity |
| IR @ VWM | <1 μA - Ultra-low reverse leakage ensures minimal standby power loss in high-impedance circuits |
| Package | DO-214AC (SMA) - Industry-standard surface-mount outline with 0.060g mass and UL 94V-0 molding compound |
Pinout & Package
DO-214AC (SMA) package: cathode-banded unidirectional configuration with two terminals - anode (non-banded end) and cathode (banded end). Matte tin-plated leads meet J-STD-002 solderability and JESD201 Class 2 whisker requirements.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Forward conduction terminal | Connected to lower-potential side (e.g., ground or return path) in unidirectional TVS configuration |
| Cathode | Avalanche clamping terminal | Connected to protected line (e.g., 78V rail); conducts surge current to anode when VAK exceeds VBR |
Key Features
| Feature | Design Value |
|---|---|
| AEC-Q101 qualified | Validated for automotive electronics per stress test requirements including HTOL, TC, HAST, and UHST |
| ISO 7637-2 compliant | Withstands Pulse 1 (inductive load dump), Pulse 2a/2b (switching transients), and Pulse 3a/3b (capacitive coupling) without degradation |
| Fast response time | <1.0 ps from 0 V to VBR min, enabling protection of high-speed digital interfaces and sensitive analog front-ends |
| Moisture sensitivity level 1 | No floor life limitation or bake requirement prior to reflow - simplifies SMT manufacturing flow |
| Halogen-free & RoHS | Complies with IEC 61249-2-21 and EU RoHS Directive 2011/65/EU for green electronics manufacturing |
Applications
| Automotive Power Distribution | Industrial DC/DC Converters |
|---|---|
Use Scenario: Protection of 72–80V battery-fed control modules against load dump and alternator transients. IC Role / Device Role / Timing Role: Unidirectional TVS placed across input rails to clamp surges up to 139V while maintaining <1μA leakage at nominal 78V operation. Use Value: Enables compliance with ISO 7637-2 Pulse 1 (−150V/0.5Ω) without derating or parallel staging. | Use Scenario: Input-side surge suppression in isolated 48–96V input DC/DC converters used in factory automation PLCs. IC Role / Device Role / Timing Role: Standoff-rated TVS absorbing repetitive 10/1000μs transients from relay switching or motor drive feedback coupling. Use Value: Maintains system uptime by preventing MOSFET gate oxide failure and controller latch-up during field-deployed operation. |
| Telecom Power Supplies | LED Driver Front-Ends |
Use Scenario: Secondary-side overvoltage protection in telecom rectifier modules operating from –48V DC distribution buses. IC Role / Device Role / Timing Role: Bidirectional-capable variant not required; unidirectional SMAJ78H used with polarity-aware layout to protect negative-rail referenced circuits. Use Value: Delivers 400W pulse rating at 25°C with <3.5V forward voltage at 25A, minimizing conduction loss during fault events. | Use Scenario: Surge hardening of constant-current LED drivers in streetlight systems exposed to lightning-induced surges on long feeder lines. IC Role / Device Role / Timing Role: Primary clamping device placed between AC-DC output and LED string input to limit transient energy entering driver ICs. Use Value: Clamps to 139V within <1ps, preventing catastrophic failure of high-voltage GaN FETs and current-sense amplifiers. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient voltage suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMAJ78A | Lower VBR range (86.7–95.8 V), tighter tolerance, same VC = 126 V at 3.2A | Better suited for precision-clamp designs where lower clamping voltage margin is critical | Select SMAJ78A when design requires reduced clamping overshoot at cost of slightly lower minimum breakdown margin |
| SMBJ78H | Same VWM/VBR specs but SMB package (DO-214AA), 600W PPPM, higher IPPM | Used where higher surge robustness is needed and PCB space allows larger footprint | Choose SMBJ78H only if board layout permits DO-214AA and system-level testing demands >400W pulse handling |
Compared with SMAJ78H, SMAJ78A offers tighter VBR control and lower clamping voltage but reduced surge margin, while SMBJ78H provides higher pulse power in a larger package - neither is pin-compatible, and both require layout revision.
Availability
SMAJ78H is available at Aetrix Electronics and suitable for automotive power distribution, industrial DC/DC converters, telecom power supplies, and LED driver front-ends requiring stable component supply with full AEC-Q101 traceability and ISO 7637-2 validation.
Supply support for SMAJ78H 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 semiconductor manufacturer specializing in discrete power devices, TVS diodes, rectifiers, and MOSFETs for automotive, industrial, and consumer markets.
The SMAJ series was developed specifically for AEC-Q101-compliant transient suppression in 12V–188V automotive and industrial systems, emphasizing reliability under ISO 7637-2 pulse stress and high-volume SMT manufacturability.
FAQ
What is the maximum clamping voltage of the SMAJ78H under standard test conditions?
The SMAJ78H has a maximum clamping voltage (VC) of 139 V at 2.9 A peak impulse current (IPPM) using the 10/1000μs waveform. This value is measured per JEDEC standards and defines the upper voltage limit imposed on protected circuits during surge events. The SMAJ78H maintains this clamping performance across its specified operating temperature range and is validated for repeated surge exposure in automotive environments.
Is the SMAJ78H suitable for bidirectional transient protection?
No, the SMAJ78H is a unidirectional TVS diode intended for polarity-specific surge suppression. For bidirectional applications, Taiwan Semiconductor specifies the SMAJ78CH or SMAJ78CAH variants - which feature symmetrical breakdown in both directions. Using SMAJ78H in reverse-biased configurations risks premature failure due to lack of reverse avalanche capability. Always verify polarity alignment during PCB layout for SMAJ78H.
Does the SMAJ78H meet automotive qualification standards?
Yes, the SMAJ78H is AEC-Q101 qualified and tested per the full stress test schedule including high-temperature operating life (HTOL), temperature cycling (TC), unbiased highly accelerated stress test (UHAST), and humidity bias HAST. It also complies with ISO 7637-2 for Pulse 1, 2a, 2b, 3a, and 3b, making it suitable for engine control units, body control modules, and other automotive electronic systems requiring certified transient protection.
What is the moisture sensitivity level (MSL) rating for the SMAJ78H?
The SMAJ78H carries a moisture sensitivity level (MSL) rating of Level 1 per J-STD-020, meaning it has unlimited floor life and does not require dry pack or baking prior to reflow soldering. This simplifies manufacturing logistics and eliminates moisture-related popcorning risk during standard lead-free reflow profiles - a key advantage for high-reliability automotive and industrial assembly lines.
How does the SMAJ78H compare to the SMAJ78AH variant?
The SMAJ78AH features a tighter breakdown voltage range (86.7–95.8 V vs. 86.7–106 V for SMAJ78H) and lower clamping voltage (126 V at 3.2 A vs. 139 V at 2.9 A), resulting in improved precision clamping but reduced minimum breakdown margin. Both share identical DO-214AC packaging, AEC-Q101 qualification, and ISO 7637-2 compliance. Designers select SMAJ78AH when clamping accuracy outweighs worst-case surge margin requirements.
SMAJ78H Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Taiwan Semiconductor Corporation
- Package/Case:
- DO-214AC, SMA
- Series:
- SMAJ
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Type:
- Zener
- Unidirectional Channels:
- 1
- Bidirectional Channels:
- -
- Voltage - Reverse Standoff (Typ):
- 78V
- Voltage - Breakdown (Min):
- 86.7V
- Voltage - Clamping (Max) @ Ipp:
- 139V
- Current - Peak Pulse (10/1000µs):
- 2.9A
- Power - Peak Pulse:
- 400W
- Power Line Protection:
- No
- Applications:
- -
- Capacitance @ Frequency:
- -
- Operating Temperature:
- -55°C ~ 150°C (TJ)
- Grade:
- Automotive
- Qualification:
- AEC-Q101
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- DO-214AC (SMA)
SMAJ78H FAQ
1.How can I place an order for SMAJ78H through Aetrix?
Please submit a Request for Quotation (RFQ) for SMAJ78H 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 SMAJ78H reliable?
The price and inventory of SMAJ78H are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMAJ78H is usually 5 days.
3.What payment methods are accepted for SMAJ78H?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMAJ78H transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMAJ78H?
SMAJ78H orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMAJ78H 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 SMAJ78H?
For technical support, including SMAJ78H datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMAJ78H requirements.
6.How does Aetrix verify that SMAJ78H is sourced from the original manufacturer or authorized distributors?
All SMAJ78H 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 SMAJ78H meets industry standards.
7.What is the process for return or replacement of SMAJ78H?
All SMAJ78H units undergo pre-shipment inspection (PSI). If there is an issue with SMAJ78H, 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 SMAJ78H part is unused and in its original packaging.
Return procedure for SMAJ78H:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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