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Alpha & Omega Semiconductor Inc. SMDJ21A
- Part No.:
- SMDJ21A
- Manufacturer:
- Alpha & Omega Semiconductor Inc.
- Category:
- TVS Diodes
- Package:
- DO-214AB, SMC
- Datasheet:
-
SMDJ21A.pdf
- Description:
- 1CH 21V UNIDIRECTIONAL 3000W SMD
- Quantity:
- Payment:
- Shipping:
Inventory:6,647
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Product details
Overview
SMDJ21A from Alpha & Omega Semiconductor is a unidirectional transient voltage suppressor diode (TVS) designed for robust overvoltage protection in DC power rails and signal lines. It features a 21.0 V reverse stand-off voltage (VRWM), 23.31–25.73 V breakdown voltage (VBR) at 1 mA, 34.1 V maximum clamping voltage (VC) at 88.0 A peak pulse current, and 3000 W peak pulse power dissipation on a 10/1000 µs waveform - deployed in industrial motor drives, telecom power supplies, and automotive body control modules.
For engineers reviewing the SMDJ21A datasheet, pinout, applications, or equivalent options, key selection criteria include clamping performance under 88 A surge, thermal resistance (RθJA = 75 °C/W), unidirectional polarity with cathode band marking, DO-214AB package compatibility, and compliance with J-STD-020 MSL Level 1 reflow requirements.
Technical Context
The SMDJ21A operates as a silicon avalanche diode optimized for fast transient suppression. Its glass-passivated junction enables sub-1 ps response time from 0 V to breakdown, while its low-profile DO-214AB (SMC J-Bend) package supports high-density surface-mount layouts with built-in strain relief and matte tin lead-free plating.
Rated for -55 °C to +150 °C junction temperature, it delivers stable clamping across ambient conditions with a typical VBR temperature coefficient of 0.1% × VBR per °C change. Electrical characteristics are specified for unidirectional operation only; bidirectional variants (e.g., SMDJ21CA) are separate part numbers with identical VRWM and VC but symmetrical conduction.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VRWM | 21.0 V - Maximum continuous reverse operating voltage before significant leakage; sets upper limit for protected circuit's normal DC rail. |
| VBR @ IT=1 mA | 23.31–25.73 V - Confirmed avalanche onset range; ensures reliable triggering above system nominal voltage with margin. |
| VC @ IPPM=88.0 A | 34.1 V - Clamped voltage during 10/1000 µs surge; defines worst-case stress on downstream ICs during ESD/EFT events. |
| PPPM | 3000 W - Peak pulse power handling on standard 10/1000 µs waveform; validates suitability for IEC 61000-4-5 Level 4 surges. |
| TJ max | +150 °C - Maximum junction temperature; enables use in high-ambient environments like engine compartments or enclosed power converters. |
| RθJA | 75 °C/W - Thermal resistance junction-to-ambient on standard 8 mm × 8 mm copper pads; informs heatsinking requirements for repetitive surge duty. |
Pinout & Package
DO-214AB (SMC J-Bend) surface-mount package: molded plastic case with J-bend leads, JEDEC-compliant outline, matte tin lead-free plating, and cathode indicated by color band (anode unmarked). Mounting requires soldering per MIL-STD-750 Method 2026.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Low-side connection point | Connected to ground or lower-potential node; completes clamping path during positive transients. |
| Cathode | High-side connection point | Marked with color band; connected to protected line (e.g., 24 V rail); conducts avalanche current when line exceeds VRWM. |
Key Features
| Feature | Design Value |
|---|---|
| Fast response time | <1.0 ps - Enables suppression of nanosecond-scale ESD pulses before sensitive logic or analog circuits are damaged. |
| Glass passivated junction | Improved reliability and stable VBR over lifetime - reduces parameter drift due to moisture ingress or thermal cycling. |
| MSL Level 1 rating | Reflow-compatible up to 260 °C peak - eliminates pre-baking requirement and supports standard SMT assembly processes. |
| UL 94V-0 flammability | Self-extinguishing plastic housing - meets safety standards for enclosed industrial and automotive enclosures. |
Applications
| Industrial Motor Drives | Telecom Power Supplies |
|---|---|
Use Scenario: Protection of 24 V DC control inputs against load dump and inductive switching transients in PLC I/O modules. IC Role / Device Role / Timing Role: Unidirectional TVS placed between input terminal and chassis ground to clamp surges exceeding 21 V. Use Value: Limits transient voltage to ≤34.1 V at 88 A, preventing latch-up or gate oxide damage in microcontrollers and optocouplers. | Use Scenario: Input-stage surge protection on 48 V primary side of AC/DC front-end rectifiers in base station power systems. IC Role / Device Role / Timing Role: Standoff-rated TVS absorbing IEC 61000-4-5 combination wave surges without degradation. Use Value: 3000 W peak power rating sustains multiple 10/1000 µs surges without parametric shift or thermal runaway. |
| Automotive Body Control | Renewable Energy Inverters |
Use Scenario: CAN bus power line protection in door module ECUs exposed to battery disconnect transients. IC Role / Device Role / Timing Role: Unidirectional clamping device on 12 V supply rail upstream of CAN transceiver LDO. Use Value: 23.31–25.73 V VBR ensures no conduction during cold-crank (6.5 V) or load-dump (up to 20 V), yet triggers reliably at surge onset. | Use Scenario: DC-link overvoltage suppression in solar string inverters subjected to lightning-induced surges on PV input. IC Role / Device Role / Timing Role: Primary TVS on MPPT input stage, coordinated with MOVs for multi-level protection. Use Value: DO-214AB footprint allows parallel placement with minimal PCB area; RθJA = 75 °C/W supports natural convection cooling in sealed enclosures. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient voltage suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SAC21A (Littelfuse) | Same DO-214AB package, VRWM = 21 V, VC = 34.5 V @ 87 A, but higher IR = 5 µA @ VRWM vs. 2 µA for SMDJ21A. | Higher leakage may affect ultra-low-power sensor nodes; otherwise functionally interchangeable in 24 V rail protection. | Select SAC21A if dual-sourcing required and minor leakage increase is acceptable. |
| SMCJ21A (ON Semiconductor) | Identical VRWM/VBR/VC ratings and DO-214AB package; differs in thermal resistance (RθJA = 65 °C/W vs. 75 °C/W) and peak surge current (89.3 A vs. 88.0 A). | Better thermal performance allows tighter layout spacing in thermally constrained designs; same clamping behavior. | Choose SMCJ21A where board-level thermal management is marginal and lower RθJA improves long-term reliability. |
Compared with SAC21A and SMCJ21A, the SMDJ21A offers the lowest reverse leakage (2 µA) at VRWM and is optimized for high-volume automated assembly with MSL Level 1 and matte tin plating - making it preferred for cost-sensitive industrial controls where leakage and process compatibility are critical.
Availability
SMDJ21A is available at Aetrix Electronics and suitable for industrial motor drives, telecom power supplies, and automotive body control modules requiring stable component supply, consistent surge performance, and RoHS-compliant manufacturing.
Supply support for SMDJ21A 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
Alpha & Omega Semiconductor (AOS) is a fabless power semiconductor company specializing in MOSFETs, TVS diodes, and power ICs for efficiency-critical applications.
The SMDJxxxA series was developed specifically for high-power transient suppression in harsh-environment DC systems, emphasizing rugged packaging, tight VBR tolerance, and repeatable clamping under repetitive surge stress.
FAQ
What is the maximum clamping voltage of the SMDJ21A under a 10/1000 µs surge?
The SMDJ21A has a maximum clamping voltage (VC) of 34.1 V when subjected to its rated peak pulse current of 88.0 A on a 10/1000 µs waveform. This value is measured per industry-standard test conditions and defines the upper voltage limit imposed on protected circuitry during transient events - critical for ensuring downstream components like microcontrollers or interface ICs remain within absolute maximum ratings. The SMDJ21A maintains this clamping performance across its full operating temperature range.
Is the SMDJ21A suitable for bidirectional transient protection?
No, the SMDJ21A is a unidirectional TVS diode intended only for DC line protection with defined polarity. For bidirectional applications such as AC lines or differential data buses, the SMDJ21CA variant must be used - it shares the same VRWM (21 V) and VC (34.1 V) but conducts symmetrically in both directions. Using the SMDJ21A in a bidirectional configuration risks failure during negative-going transients, as it lacks reverse conduction capability.
What is the thermal resistance of the SMDJ21A, and how does it impact layout design?
The SMDJ21A has a typical junction-to-ambient thermal resistance (RθJA) of 75 °C/W when mounted on 8.0 mm × 8.0 mm copper pads per terminal. This value directly determines allowable power dissipation under steady-state or repetitive surge conditions - for example, sustained 1 W dissipation raises junction temperature by 75 °C above ambient. Layouts should maintain minimum pad size and avoid thermal isolation; adding internal copper planes or thermal vias improves heat spreading and lowers effective RθJA in practice.
Does the SMDJ21A meet lead-free and RoHS compliance requirements?
Yes, the SMDJ21A is a certified AOS Green Product: fully RoHS compliant, halogen-free, and lead-free with matte tin-plated terminals. It conforms to J-STD-020 MSL Level 1, supporting peak reflow temperatures up to 260 °C without preconditioning. The device carries UL 94V-0 flammability rating and is qualified for high-reliability industrial and automotive applications where environmental compliance is mandatory - all verified per AOS' published green policy documentation.
How does the SMDJ21A's breakdown voltage tolerance affect circuit design margins?
The SMDJ21A specifies a breakdown voltage (VBR) range of 23.31 V to 25.73 V at 1 mA test current - a ±5% tolerance around the nominal 24.5 V midpoint. This tolerance must be accounted for in system-level overvoltage margining: for instance, a 24 V nominal rail must ensure that even the lowest VBR (23.31 V) exceeds expected operating transients (e.g., cold-crank dips), while the highest VBR (25.73 V) remains safely below the absolute maximum rating of protected ICs. Designers commonly use the min/max VBR values to set worst-case clamping bounds in SPICE simulations and FMEA analysis for the SMDJ21A.
SMDJ21A Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Alpha & Omega Semiconductor Inc.
- Package/Case:
- DO-214AB, SMC
- Series:
- -
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Type:
- Zener
- Unidirectional Channels:
- 1
- Bidirectional Channels:
- -
- Voltage - Reverse Standoff (Typ):
- 21V
- Voltage - Breakdown (Min):
- 23.31V
- Voltage - Clamping (Max) @ Ipp:
- 34.1V
- Current - Peak Pulse (10/1000µs):
- 88A
- Power - Peak Pulse:
- 3000W (3kW)
- 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-214AB
SMDJ21A FAQ
1.How can I place an order for SMDJ21A through Aetrix?
Please submit a Request for Quotation (RFQ) for SMDJ21A 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 SMDJ21A reliable?
The price and inventory of SMDJ21A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMDJ21A is usually 5 days.
3.What payment methods are accepted for SMDJ21A?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMDJ21A transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMDJ21A?
SMDJ21A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMDJ21A 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 SMDJ21A?
For technical support, including SMDJ21A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMDJ21A requirements.
6.How does Aetrix verify that SMDJ21A is sourced from the original manufacturer or authorized distributors?
All SMDJ21A 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 SMDJ21A meets industry standards.
7.What is the process for return or replacement of SMDJ21A?
All SMDJ21A units undergo pre-shipment inspection (PSI). If there is an issue with SMDJ21A, 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 SMDJ21A part is unused and in its original packaging.
Return procedure for SMDJ21A:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SMDJ21A Tags
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