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Taiwan Semiconductor Corporation SA78H
- Part No.:
- SA78H
- Manufacturer:
- Taiwan Semiconductor Corporation
- Category:
- TVS Diodes
- Package:
- DO-204AC, DO-15, Axial
- Datasheet:
-
SA78H.pdf
- Description:
- 500W, 94.9V, 10%, UNIDIRECTIONAL
- Quantity:
- Payment:
- Shipping:
Inventory:8,885
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Product details
Overview
SA78H from Taiwan Semiconductor is a unidirectional 500W transient voltage suppressor (TVS) diode in DO-204AC (DO-15) package, with 78V working stand-off voltage (VWM), 86.7–103V breakdown voltage (VBR @ 1mA), and 139V maximum clamping voltage (VC) at 3.7A peak pulse current. It delivers AEC-Q101 qualification for automotive-grade surge protection in power supply rails and interface lines.
For engineers reviewing the SA78H datasheet, SA78H pinout, SA78H application, or SA78H equivalent, this device is selected for high-reliability DC bus protection where fast clamping (<1.0ps response), low leakage (<1μA @ 78V), and 175°C junction temperature capability are critical design requirements.
Technical Context
The SA78H operates as a unidirectional avalanche diode, triggered when reverse voltage exceeds its VBR range (86.7–103V). Its clamping action limits transients to ≤139V at 3.7A under 10/1000μs waveform, enabling robust protection of downstream 72–80V systems such as automotive 24V+ battery rails and industrial DC power inputs.
It features pure tin-plated leads compliant with J-STD-002, UL 94V-0 molding compound, and meets JESD201 Class 2 whisker resistance. The device is rated for -55°C to +175°C operating junction temperature and supports steady-state power dissipation of 3W at TL = 75°C on 10×10 mm copper pads.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VWM | 78 V - Maximum continuous reverse operating voltage before clamping begins; sets threshold for 24V+ automotive and industrial DC systems. |
| VBR min/max | 86.7 / 103 V @ 1 mA - Breakdown voltage range defines turn-on consistency; ensures reliable triggering across temperature and unit variation. |
| VC @ IPPM | 139 V @ 3.7 A - Clamping voltage under 10/1000μs surge; determines maximum stress imposed on protected ICs or MOSFETs. |
| PPK | 500 W - Peak pulse power rating per 10/1000μs waveform; defines single-event surge energy handling capacity. |
| IR @ VWM | <1 μA - Reverse leakage at 78V; minimizes standby power loss and avoids false triggering in high-impedance circuits. |
| TJ max | +175 °C - Maximum junction temperature; enables operation in under-hood automotive and high-ambient industrial environments. |
| Package | DO-204AC (DO-15) - Standard axial-leaded through-hole package with cathode band marking; compatible with legacy PCB layouts and wave soldering. |
Pinout & Package
DO-204AC (DO-15) package: axial-leaded, molded epoxy case with cathode band marking. Leads are pure tin-plated, solderable per J-STD-002, and meet JESD201 Class 2 whisker resistance. Weight ≈ 0.400 g.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Forward conduction terminal | Connected to system ground or low-side return path; conducts during forward surge events (e.g., reverse polarity faults). |
| Cathode | Reverse-biased clamping terminal | Connected to protected line (e.g., 24V rail); avalanches into conduction when transient exceeds VBR, shunting energy to ground. |
Key Features
| Feature | Design Value |
|---|---|
| AEC-Q101 qualified | Validated for automotive applications including engine control units, body electronics, and ADAS power domains. |
| Clamping voltage ≤139 V | Ensures protected 72–80V circuits remain within safe operating area during ISO 7637-2 Pulse 1/2/5a surges. |
| Response time <1.0 ps | Enables sub-nanosecond suppression of ESD and fast transients, preventing latch-up or gate oxide damage in sensitive ICs. |
| RoHS & halogen-free | Complies with IEC 61249-2-21; suitable for green manufacturing and export-regulated end equipment. |
| 175°C TJ max | Supports placement near heat sources (e.g., power converters) without derating in harsh thermal environments. |
Applications
| Automotive Power Rail Protection | Industrial DC Input Protection |
|---|---|
Use Scenario: Protecting 24V+ battery-fed ECUs from load dump and alternator transients per ISO 7637-2. IC Role / Device Role / Timing Role: Unidirectional TVS placed between battery rail and input filter capacitor to clamp surges above 78V. Use Value: Limits peak voltage to ≤139V during 500W 10/1000μs pulses, preserving downstream DC-DC controllers and microcontrollers. | Use Scenario: Safeguarding programmable logic controller (PLC) 48V DC inputs against inductive switching spikes from solenoids and relays. IC Role / Device Role / Timing Role: Standoff protector on field-side input terminals, absorbing repetitive 100–500W transients without degradation. Use Value: Maintains <1μA leakage at 78V, avoiding false triggers in high-impedance sensing circuits while surviving >10,000 surge events. |
| LED Driver Overvoltage Clamp | Telecom Power Interface Protection |
Use Scenario: Preventing catastrophic failure of constant-current LED drivers subjected to accidental 120V AC coupling or lightning-induced surges. IC Role / Device Role / Timing Role: Primary clamping element on driver input, placed upstream of bulk capacitor and PWM controller. Use Value: Fast <1.0ps response captures initial voltage spike before controller ICs respond, reducing required MOV coordination margin. | Use Scenario: Securing PoE-powered device (e.g., IP camera) DC input against Ethernet cable-induced surges and hot-swap transients. IC Role / Device Role / Timing Role: First-line unidirectional suppressor on PSE-side DC feed, coordinated with secondary TVS and common-mode chokes. Use Value: 139V clamping ensures compliance with IEEE 802.3bt Type 4 surge immunity (100V test level) while supporting 78V nominal operation. |
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 | Same DO-214AC package; lower PPK (400W); higher VC (126V @ 3.2A); no AEC-Q101 qualification. | Targeted at commercial/industrial use only; not validated for automotive temperature cycling or vibration. | Select SMAJ78A only if AEC-Q101 is not required and 400W surge rating suffices for the application. |
| P6SMB78A | DO-214AA package; same 78V VWM; PPK = 600W; VC = 126V @ 4.8A; AEC-Q101 available in "-Q" variant. | Higher surge margin but larger footprint; requires PCB layout change due to different lead spacing and body size. | Choose P6SMB78A-Q if higher 600W rating is needed and DO-214AA mounting is acceptable. |
Compared with SMAJ78A and P6SMB78A, the SA78H uniquely combines AEC-Q101 qualification, DO-204AC (DO-15) compatibility, and precise 500W/139V clamping performance-making it optimal for space-constrained automotive modules requiring drop-in replacement of legacy axial TVS diodes.
Availability
SA78H is available at Aetrix Electronics and suitable for automotive power rail protection, industrial DC input protection, LED driver overvoltage clamp, and telecom power interface protection requiring stable component supply and long-term lifecycle support.
Supply support for SA78H 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 analog and discrete semiconductor manufacturer headquartered in Hsinchu, Taiwan, specializing in power devices, TVS diodes, rectifiers, and MOSFETs since 1979.
The SA Series is TSC's AEC-Q101-qualified transient voltage suppressor family designed specifically for automotive and industrial DC power line protection, emphasizing high surge robustness, tight parameter distribution, and extended temperature reliability.
FAQ
What is the clamping voltage of SA78H under standard 10/1000μs surge conditions?
The SA78H has a maximum clamping voltage (VC) of 139 V at 3.7 A peak pulse current under the 10/1000μs waveform. This value is measured per ANSI/IEEE C62.35 and guarantees that protected circuitry sees no more than 139 V during a 500W transient event. The SA78H datasheet specifies this parameter in the "Maximum Ratings and Electrical Characteristics" table on page 4.
Is SA78H suitable for bidirectional surge protection applications?
No, SA78H is a unidirectional TVS diode intended for DC line protection with defined polarity. Its cathode band marking indicates the clamping terminal, and it does not provide symmetrical breakdown in both directions. For bidirectional protection, the SA78CA variant (not SA78H) must be used. The SA78H datasheet explicitly states polarity as "as marked" and lists only unidirectional parameters.
Does SA78H meet automotive qualification standards?
Yes, SA78H is AEC-Q101 qualified, as confirmed in the "Features" section and ordering code definition ("H" suffix denotes AEC-Q101 qualification). It is tested for temperature cycling, humidity bias, mechanical shock, and accelerated life under high-temperature reverse bias per AEC-Q101 Rev D. This makes SA78H suitable for under-hood and chassis-mounted automotive modules.
What is the maximum steady-state power dissipation for SA78H at board temperature?
The SA78H has a steady-state power dissipation (PD) rating of 3 W when mounted on 10 × 10 mm copper pads per lead at TL = 75°C. This value assumes proper thermal land design and accounts for conduction losses during sustained reverse leakage or forward conduction. Derating is required above 75°C per the Pulse Derating Curve (Fig.2) in the SA78H datasheet.
How does the SA78H compare to SA78A in terms of electrical performance?
The SA78H and SA78A share identical VWM (78 V), VBR (86.7–103 V), and VC (139 V) specifications, but SA78H adds AEC-Q101 qualification and tighter process controls for automotive use. SA78A lacks the "H" suffix and is intended for commercial/industrial applications only. Both use DO-204AC packaging and have identical pinout and thermal characteristics.
SA78H Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Taiwan Semiconductor Corporation
- Package/Case:
- DO-204AC, DO-15, Axial
- Series:
- SA
- 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):
- 3.7A
- Power - Peak Pulse:
- 500W
- Power Line Protection:
- No
- Applications:
- -
- Capacitance @ Frequency:
- -
- Operating Temperature:
- -55°C ~ 175°C (TJ)
- Grade:
- Automotive
- Qualification:
- AEC-Q101
- Mounting Type:
- Through Hole
- Supplier Device Package:
- DO-204AC (DO-15)
SA78H FAQ
1.How can I place an order for SA78H through Aetrix?
Please submit a Request for Quotation (RFQ) for SA78H 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 SA78H reliable?
The price and inventory of SA78H are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SA78H is usually 5 days.
3.What payment methods are accepted for SA78H?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SA78H transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SA78H?
SA78H orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SA78H 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 SA78H?
For technical support, including SA78H datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SA78H requirements.
6.How does Aetrix verify that SA78H is sourced from the original manufacturer or authorized distributors?
All SA78H 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 SA78H meets industry standards.
7.What is the process for return or replacement of SA78H?
All SA78H units undergo pre-shipment inspection (PSI). If there is an issue with SA78H, 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 SA78H part is unused and in its original packaging.
Return procedure for SA78H:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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