My Inquiry
My Account
Taiwan Semiconductor Corporation SMBJ78A
- Part No.:
- SMBJ78A
- Manufacturer:
- Taiwan Semiconductor Corporation
- Category:
- TVS Diodes
- Package:
- DO-214AA, SMB
- Datasheet:
-
SMBJ78A.pdf
- Description:
- TVS DIODE 78VWM 126VC DO214AA
- Quantity:
- Payment:
- Shipping:
Inventory:6,000
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
SMBJ78A from Taiwan Semiconductor is a unidirectional 600W surface-mount transient voltage suppressor (TVS) diode in DO-214AA (SMB) package, designed for high-energy surge protection in DC power lines and signal paths. It features a 78V working stand-off voltage (VWM), 86.7–95.8V breakdown voltage (VBR), 126V maximum clamping voltage (VC) at 5.0A peak impulse current, and <1μA leakage above 10V - deployed in automotive power supply rails and industrial I/O interfaces.
For engineers reviewing the SMBJ78A datasheet, SMBJ78A pinout, SMBJ78A application, or SMBJ78A equivalent, key selection criteria include clamping performance under 10/1000µs transients, thermal derating above 25°C ambient, unidirectional polarity marking, and compliance with ISO 7637-2 Pulse 1/2a/2b/3a/3b for automotive ESD and load-dump immunity.
Technical Context
The SMBJ78A operates as a silicon avalanche diode with glass-passivated junction, delivering sub-1ps response to fast-rising transients. Its unidirectional configuration enables asymmetric clamping - forward conduction only during reverse overvoltage events - and supports steady-state power dissipation up to 3W at 25°C ambient.
Thermal performance is defined by 10°C/W junction-to-case (RθJC) and 55°C/W junction-to-ambient (RθJA) resistance. Electrical behavior follows ANSI/IEEE C62.35 standards, with VBR tested at 1mA IT and VC measured at specified IPP under 10/1000µs waveform per Fig.3.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VWM | 78 V - Maximum continuous DC or RMS voltage the device blocks without clamping; sets operating margin below breakdown. |
| VBR min/max | 86.7 V / 95.8 V @ 1 mA - Confirmed avalanche onset range; ensures reliable turn-on before system damage threshold. |
| VC @ IPP | 126 V @ 5.0 A - Clamped voltage during 10/1000µs surge; defines worst-case overvoltage seen by protected IC. |
| PPK | 600 W - Peak pulse power handling per single non-repetitive 10/1000µs event; determines surge energy absorption capacity. |
| ID @ VWM | <1 µA - Reverse leakage at rated stand-off; negligible power loss and minimal impact on high-impedance sensing nodes. |
| TJ max | +150 °C - Maximum junction temperature; enables operation in under-hood automotive or enclosed industrial enclosures. |
| Package | DO-214AA (SMB) - Standardized surface-mount outline with cathode band marking; compatible with automated reflow assembly. |
Pinout & Package
DO-214AA (SMB) package: molded plastic case with matte tin-plated leads, polarity indicated by cathode band on one end. Weight ≈0.090g. Meets UL 94V-0 flammability and JESD201 Class 2 whisker resistance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Forward current entry / Cathode-banded side opposite | Connected to system ground or low-side return path; conducts during reverse transient to clamp voltage. |
| Cathode | Reverse voltage sensing / Marked end | Connected to protected line (e.g., 24V rail); avalanche breakdown initiates here when voltage exceeds VBR. |
Key Features
| Feature | Design Value |
|---|---|
| Glass-passivated junction | Ensures stable VBR over temperature and long-term reliability in humid or thermally cycled environments. |
| Clamping voltage ≤126 V @ 5.0 A | Provides predictable overvoltage limiting for 75–80V nominal systems (e.g., 24V/48V automotive), preventing MOSFET gate oxide rupture. |
| Response time <1 ps | Engages before most microsecond-scale transients (e.g., relay bounce, inductive kick) propagate into sensitive logic. |
| ISO 7637-2 compliant | Validated for Pulse 1 (inductive load disconnect), Pulse 2a (sudden load dump), and Pulse 3a/b (switching noise) in automotive ECUs. |
| Moisture sensitivity level 1 | Eliminates bake requirements prior to SMT reflow; supports standard JEDEC moisture handling protocols. |
Applications
| Automotive Power Rail Protection | Industrial PLC Digital Input Protection |
|---|---|
Use Scenario: 24V battery-fed control module exposed to load-dump surges up to 120V during alternator regulation failure. IC Role / Device Role / Timing Role: Unidirectional TVS placed between input fuse and DC-DC converter input to clamp transients before LDO or buck regulator. Use Value: Limits voltage to ≤126V during 600W 10/1000µs pulse, preserving downstream power management ICs rated for 36V absolute max. |
Use Scenario: 24V digital input channel receiving signals from field sensors subject to EFT bursts per IEC 61000-4-4. IC Role / Device Role / Timing Role: Front-end protection element shunting fast transients before optocoupler or Schmitt trigger input stage. Use Value: Sub-1ps response prevents false triggering; <1µA leakage avoids bias current errors in high-impedance current-loop interfaces. |
| LED Driver Output Protection | RS-485 Transceiver Bus Line Protection |
Use Scenario: Constant-current LED driver output subjected to inductive switching spikes from nearby solenoid actuation. IC Role / Device Role / Timing Role: Parallel-connected TVS across LED string terminals to absorb flyback energy from parasitic inductance. Use Value: 600W peak power rating handles repetitive 100ns–1µs spikes without thermal runaway; DO-214AA footprint fits tight board spacing. |
Use Scenario: RS-485 half-duplex bus (A/B lines) routed through noisy factory floor with frequent ESD events and cable-induced surges. IC Role / Device Role / Timing Role: Bidirectional protection not applicable - SMBJ78A used on isolated power rail feeding transceiver, not data lines. Use Value: Clamps 78V rail to ≤126V during 5A surge, maintaining clean VCC for MAX13487-level transceivers requiring stable 5V/3.3V supply. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| Littelfuse SMAJ78A | Same DO-214AC (SMA) package; 126V VC @ 5.0A; 55°C/W RθJA vs. SMBJ78A's 55°C/W; identical VWM/VBR specs. | SMA package has smaller footprint (4.5 × 2.7 mm vs. SMB's 4.6 × 3.9 mm) but lower power density; less robust for repeated 600W surges. | Select SMAJ78A only if board space is constrained and surge duty cycle is light; SMBJ78A preferred for automotive under-hood use. |
| Vishay SM8S78A | DO-214AB (SMC) package; 600W rating; 126V VC @ 5.0A; higher IFSM (200A vs. 100A); RθJA = 35°C/W - superior thermal performance. | SMC package requires larger PCB pad area but enables higher sustained surge repetition rates and better heat spreading in metal-core boards. | Choose SM8S78A for high-reliability industrial motor drives where thermal cycling and multi-pulse events dominate; SMBJ78A balances cost and performance for single-event protection. |
Compared with SMAJ78A and SM8S78A, SMBJ78A delivers optimal cost-performance trade-off in DO-214AA: larger than SMA but smaller than SMC, with verified 600W capability, ISO 7637-2 compliance, and industry-standard reflow compatibility - making it ideal for volume automotive and industrial control designs.
Availability
SMBJ78A is available at Aetrix Electronics and suitable for automotive ECU power rail protection, industrial PLC digital input conditioning, and LED driver output surge suppression requiring stable component supply across extended temperature ranges and high-volume production.
Supply support for SMBJ78A 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 TVS diodes, rectifiers, and MOSFETs for industrial and automotive markets.
The SMBJ series was developed specifically for AEC-Q200-compliant transient suppression in 12V/24V/48V vehicle subsystems and ruggedized industrial equipment, emphasizing low clamping ratio, repeatable avalanche behavior, and JEDEC-standard packaging.
FAQ
What is the maximum clamping voltage of SMBJ78A under a 10/1000µs surge?
The SMBJ78A exhibits a maximum clamping voltage (VC) of 126 V when subjected to a 5.0 A peak impulse current with a 10/1000µs waveform. This value is measured per ANSI/IEEE C62.35 and confirmed in Taiwan Semiconductor's R2104 datasheet, ensuring predictable overvoltage limiting for protected circuits downstream of the SMBJ78A.
Is SMBJ78A suitable for bidirectional transient protection?
No, SMBJ78A is a unidirectional TVS diode and must be used with correct polarity - cathode connected to the protected line, anode to ground. For bidirectional protection, Taiwan Semiconductor specifies the SMBJ78CA variant; using SMBJ78A in reverse-biased AC applications risks permanent failure due to forward conduction during positive half-cycles.
What is the leakage current specification for SMBJ78A at its working stand-off voltage?
At its 78 V working stand-off voltage (VWM), the SMBJ78A guarantees a maximum blocking leakage current (ID) of 1 µA at 25°C ambient. This low leakage preserves signal integrity in high-impedance monitoring circuits and minimizes standby power loss in always-on automotive modules.
Does SMBJ78A meet automotive surge immunity standards?
Yes, SMBJ78A meets ISO 7637-2 requirements for Pulse 1 (inductive load disconnect), Pulse 2a (sudden supply interruption), Pulse 2b (supply recovery), and Pulses 3a/3b (switching noise), as explicitly stated in the Taiwan Semiconductor SMBJ Series datasheet R2104 - validating its use in automotive body control modules and infotainment power supplies.
What is the thermal resistance from junction to ambient for SMBJ78A?
The SMBJ78A has a junction-to-ambient thermal resistance (RθJA) of 55°C/W under standard JEDEC test conditions (single device on FR-4 board, 1-inch² copper pad). This value informs derating curves in Figure 2 of the datasheet and confirms suitability for operation up to +105°C ambient when mounted with adequate copper area.
SMBJ78A Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Taiwan Semiconductor Corporation
- Package/Case:
- DO-214AA, SMB
- Series:
- SMBJ
- 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):
- 4.8A
- Power - Peak Pulse:
- 600W
- Power Line Protection:
- No
- Applications:
- General Purpose
- Capacitance @ Frequency:
- -
- Operating Temperature:
- -55°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- DO-214AA (SMB)
SMBJ78A FAQ
1.How can I place an order for SMBJ78A through Aetrix?
Please submit a Request for Quotation (RFQ) for SMBJ78A 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 SMBJ78A reliable?
The price and inventory of SMBJ78A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMBJ78A is usually 5 days.
3.What payment methods are accepted for SMBJ78A?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMBJ78A transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMBJ78A?
SMBJ78A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMBJ78A 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 SMBJ78A?
For technical support, including SMBJ78A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMBJ78A requirements.
6.How does Aetrix verify that SMBJ78A is sourced from the original manufacturer or authorized distributors?
All SMBJ78A 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 SMBJ78A meets industry standards.
7.What is the process for return or replacement of SMBJ78A?
All SMBJ78A units undergo pre-shipment inspection (PSI). If there is an issue with SMBJ78A, 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 SMBJ78A part is unused and in its original packaging.
Return procedure for SMBJ78A:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SMBJ78A Tags
-
ESD9B5.0ST5G
onsemi
-
DESD3V3E1BL-7B
Diodes Incorporated
-
ESD5Z3.3T1G
onsemi
-
D5V0H1B2LP-7B
Diodes Incorporated
-
D5V0P1B2LP-7B
Diodes Incorporated
-
DESD5V0U1BA-7
Diodes Incorporated
-
ESD5Z5.0T1G
onsemi
-
DESD5V0U1BB-7
Diodes Incorporated
-
D12V0L1B2LP-7B
Diodes Incorporated
-
PESD2V0Y1BSFYL
Nexperia USA Inc.
-
DF2S5M4CT,L3F
Toshiba Semiconductor and Storage
-
D5V0L1B2WS-7
Diodes Incorporated
Tech Hub
Counterfeit components can hide behind convincing markings and passing basic function tests. This engineering reference covers source traceability, external inspection, X-ray, XRF, electrical testing, …
A practical engineering and sourcing framework covering lifecycle verification, lifetime-buy calculations, replacement qualification, supplier checks and counterfeit-risk controls.
TTL and CMOS logic families differ in thresholds, loading, output drive, power and timing. This engineering guide compares 74HC and 74HCT, calculates noise margins and checks 3.3 V/5 V compatibility.
A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.
The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…
The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…
A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
