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Taiwan Semiconductor Corporation SMF78AH
- Part No.:
- SMF78AH
- Manufacturer:
- Taiwan Semiconductor Corporation
- Category:
- TVS Diodes
- Package:
- SOD-123W
- Datasheet:
-
SMF78AH.pdf
- Description:
- TVS DIODE 78VWM 126VC SOD123W
- Quantity:
- Payment:
- Shipping:
Inventory:4,380
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Product details
Overview
SMF78AH from Taiwan Semiconductor is a unidirectional surface-mount transient voltage suppressor (TVS) diode designed for automotive-grade ESD and surge protection in power rails and signal lines. It features a 78 V working stand-off voltage (VWM), 86.7–95.8 V breakdown voltage (VBR), 126 V clamping voltage (VC) at 1.4 A peak pulse current, and 200 W peak pulse power (10/1000 µs waveform). It is AEC-Q101 qualified and used in automotive lighting control modules.
For engineers reviewing the SMF78AH datasheet, SMF78AH pinout, SMF78AH application, or SMF78AH equivalent, key selection criteria include clamping performance under ISO 7637-2 Pulse 1/2a/2b/3a/3b, junction temperature derating above 25°C, SOD-123W package thermal resistance (RθJL = 33°C/W), and low reverse leakage (<1 µA at 78 V).
Technical Context
The SMF78AH operates as a unidirectional avalanche diode with glass-passivated junction for stable breakdown behavior and low leakage. Its clamping response is optimized for fast transients up to 10/1000 µs, delivering 126 V VC at IPPM = 1.4 A while maintaining TJ ≤ 175°C under rated conditions.
Thermal design relies on its SOD-123W package mounted on a 5 mm × 5 mm copper pad, achieving RθJA = 100°C/W and RθJL = 33°C/W - enabling reliable operation in high-ambient automotive environments without forced cooling.
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 - guaranteed avalanche initiation range at IT = 1 mA |
| VC @ IPPM | 126 V - clamped voltage during 10/1000 µs 1.4 A surge, limiting downstream stress |
| PPPM | 200 W - peak surge power handling per single 10/1000 µs pulse |
| IR @ VWM | <1 µA - minimal leakage ensures negligible standby power loss in 12/24 V systems |
| TJ max | +175°C - supports under-hood automotive placement with full derating curve |
| Package | SOD-123W - surface-mount outline with matte tin leads, J-STD-002 solderable |
Pinout & Package
SOD-123W is a two-terminal surface-mount package with cathode band marking polarity. The device has no internal circuitry beyond the single silicon die; terminals are anode (unmarked end) and cathode (banded end).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Forward conduction path | Connected to lower-potential side (e.g., ground or return rail) in unidirectional TVS configuration |
| Cathode | Avalanche clamping node | Connected to protected line (e.g., 24 V supply or LIN bus); conducts when voltage exceeds VBR |
Key Features
| Feature | Design Value |
|---|---|
| AEC-Q101 qualification | Validated for automotive use across temperature, humidity, and mechanical shock profiles per JEDEC standard |
| Glass-passivated junction | Ensures stable VBR over lifetime and immunity to moisture-induced parameter drift |
| ISO 7637-2 compliance | Withstands Pulse 1 (inductive load dump), Pulse 2a/2b (switching transients), and Pulse 3a/3b (capacitive coupling) |
| Moisture sensitivity level 1 | No floor life limitation or bake requirement prior to reflow - simplifies SMT assembly |
| Halogen-free & RoHS | Meets IEC 61249-2-21 and EU RoHS Directive 2011/65/EU for green manufacturing |
Applications
| Automotive Lighting Control | Body Control Module (BCM) Power Rail |
|---|---|
Use Scenario: Protecting LED driver ICs and microcontrollers from load-dump surges in headlamp and tail lamp assemblies. IC Role / Device Role / Timing Role: Unidirectional TVS placed between 24 V supply and ground, clamping transients before they reach sensitive logic. Use Value: Limits peak voltage to 126 V during ISO 7637-2 Pulse 1 (−120 V, 50 ms), preventing latch-up or gate oxide damage in 3.3 V/5 V controllers. | Use Scenario: Safeguarding 5 V and 12 V rails in BCMs against switching noise from solenoids, relays, and motor drivers. IC Role / Device Role / Timing Role: Standoff-rated TVS on input filter stage, absorbing repetitive 10/1000 µs pulses up to 200 W peak. Use Value: Maintains <1 µA leakage at 78 V, avoiding unnecessary current draw on always-on battery circuits while surviving >1000 surge events. |
| Infotainment System USB Port | Engine Control Unit (ECU) Sensor Interface |
Use Scenario: ESD protection for USB 2.0 data lines and VBUS in vehicle infotainment head units. IC Role / Device Role / Timing Role: Low-capacitance TVS (typ. <100 pF) placed inline with D+/D− and VBUS, grounded via short trace. Use Value: Clamps ±15 kV contact ESD (IEC 61000-4-2) to <20 V within nanoseconds, preserving signal integrity without data corruption. | Use Scenario: Transient suppression on analog sensor inputs (e.g., MAP, O2, throttle position) exposed to engine bay noise. IC Role / Device Role / Timing Role: Low-leakage TVS on 5 V reference or signal line, placed adjacent to ADC input pins. Use Value: Delivers 126 V clamping at 1.4 A while adding <0.1% gain error to 12-bit sensor measurements due to sub-µA IR. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient voltage suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMBJ78A | Higher PPPM (600 W), larger SMB package (RθJA ≈ 50°C/W), same VWM/VBR range | Better suited for higher-energy surges; requires more PCB area and thermal relief | Select SMBJ78A when system-level testing shows >200 W surge exposure or when board layout allows SMB footprint |
| P6SMB78A | Same SMB package, identical electrical specs, but not AEC-Q101 qualified | Limited to non-automotive industrial or consumer applications requiring cost-sensitive TVS | Choose P6SMB78A only for non-automotive designs where AEC-Q101 is not mandated |
Compared with SMBJ78A and P6SMB78A, the SMF78AH offers automotive qualification and compact SOD-123W packaging - enabling space-constrained placements near connectors or ICs while meeting OEM surge immunity requirements without derating penalties.
Availability
SMF78AH is available at Aetrix Electronics and suitable for automotive lighting control, body control module (BCM) power rail protection, and engine control unit (ECU) sensor interface applications requiring stable component supply and AEC-Q101 compliance.
Supply support for SMF78AH 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 SMF78AH belongs to TSC's AEC-Q101-qualified SMF series of surface-mount TVS diodes, engineered specifically for robust transient immunity in automotive power distribution and signal conditioning subsystems.
FAQ
What is the clamping voltage of SMF78AH under a 10/1000 µs surge?
The SMF78AH has a maximum clamping voltage (VC) of 126 V when subjected to a 10/1000 µs waveform at its rated peak pulse current of 1.4 A. This value is measured per standard test conditions (TA = 25°C) and is critical for ensuring downstream ICs remain within their absolute maximum voltage ratings during surge events. The SMF78AH maintains this clamping performance across its operational junction temperature range.
Is SMF78AH suitable for ISO 7637-2 Pulse 1 compliance testing?
Yes, the SMF78AH meets ISO 7637-2 Pulse 1 (inductive load dump) requirements due to its 200 W peak pulse power rating and 126 V clamping voltage. When properly mounted on a 5 mm × 5 mm copper pad, it sustains the −120 V, 50 ms transient without failure. The SMF78AH's AEC-Q101 qualification further confirms its suitability for automotive load-dump protection per OEM specifications.
What is the reverse leakage current of SMF78AH at its working voltage?
The SMF78AH exhibits a maximum reverse leakage current (IR) of 1 µA when biased at its 78 V working stand-off voltage (VWM) and tested at 25°C. This ultra-low leakage ensures minimal power loss in always-on automotive circuits, such as battery-backed sensors or real-time clocks, and contributes to long-term reliability without thermal runaway risk in the SMF78AH.
Does SMF78AH have AEC-Q101 qualification?
Yes, the SMF78AH is explicitly AEC-Q101 qualified per the manufacturer's datasheet (Version A2103). This qualification covers stress tests including temperature cycling, high-temperature operating life, unbiased highly accelerated stress testing (uHAST), and ESD (HBM ≥ 8 kV). The SMF78AH's AEC-Q101 status makes it approved for use in automotive powertrain, chassis, and body electronics where reliability is mission-critical.
What package type does SMF78AH use and what are its mounting requirements?
The SMF78AH uses the SOD-123W surface-mount package with matte tin-plated leads compliant with J-STD-002. It requires a recommended pad layout per TSC's datasheet drawing, mounted on a minimum 5 mm × 5 mm copper pad for optimal thermal performance (RθJA = 100°C/W). Reflow profile must follow J-STD-020 Level 1 moisture sensitivity guidelines - no baking needed due to MSL-1 rating.
SMF78AH Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Taiwan Semiconductor Corporation
- Package/Case:
- SOD-123W
- Series:
- SMF
- 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:
- 126V
- Current - Peak Pulse (10/1000µs):
- 1.4A
- Power - Peak Pulse:
- 200W
- Power Line Protection:
- No
- Applications:
- -
- Capacitance @ Frequency:
- -
- Operating Temperature:
- -55°C ~ 175°C (TJ)
- Grade:
- Automotive
- Qualification:
- AEC-Q101
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SOD-123W
SMF78AH FAQ
1.How can I place an order for SMF78AH through Aetrix?
Please submit a Request for Quotation (RFQ) for SMF78AH 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 SMF78AH reliable?
The price and inventory of SMF78AH are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMF78AH is usually 5 days.
3.What payment methods are accepted for SMF78AH?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMF78AH transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMF78AH?
SMF78AH orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMF78AH 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 SMF78AH?
For technical support, including SMF78AH datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMF78AH requirements.
6.How does Aetrix verify that SMF78AH is sourced from the original manufacturer or authorized distributors?
All SMF78AH 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 SMF78AH meets industry standards.
7.What is the process for return or replacement of SMF78AH?
All SMF78AH units undergo pre-shipment inspection (PSI). If there is an issue with SMF78AH, 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 SMF78AH part is unused and in its original packaging.
Return procedure for SMF78AH:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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