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onsemi 1SMB28AT3
- Part No.:
- 1SMB28AT3
- Manufacturer:
- onsemi
- Category:
- TVS Diodes
- Package:
- DO-214AA, SMB
- Datasheet:
-
1SMB28AT3.pdf
- Description:
- TVS DIODE 28VWM 45.4VC SMB
- Quantity:
- Payment:
- Shipping:
Inventory:2,430
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Product details
Overview
1SMB28AT3 from ON Semiconductor is a unidirectional 600 W peak power TVS diode designed for transient overvoltage protection in DC power rails and signal lines. It features a 28 V working peak reverse voltage (VRWM), 31.9 V minimum breakdown voltage (VBR) at 1 mA, 45.4 V maximum clamping voltage (VC) at 13.2 A peak pulse current (IPP), and sub-1 ns response time. It is used in automotive power supply inputs, industrial PLC I/O modules, and telecom interface protection.
For engineers reviewing the 1SMB28AT3 datasheet, pinout, applications, or equivalent options, key selection criteria include clamping performance under 10/1000 µs surge, UL 497B certification for isolated loop protection, low leakage (<5 µA @ 28 V), and SMB package compatibility with high-density SMT layouts.
Technical Context
The 1SMB28AT3 operates as a unidirectional Zener-based transient voltage suppressor, leveraging avalanche breakdown to clamp fast-rising transients. Its design targets single-pulse 10/1000 µs waveform compliance per IEC 61000-4-5, with thermal limits defined by junction-to-lead resistance (40 °C/W) and 150 °C max operating temperature.
It exhibits low dynamic impedance during clamping, enabling effective suppression of ESD (Class 3 HBM >16 kV) and lightning-induced surges. The device is optimized for placement directly at entry points-such as DC jacks or connector interfaces-to minimize PCB trace inductance and overshoot.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VRWM | 28 V - Maximum continuous reverse operating voltage before significant leakage; sets minimum system rail rating for safe use. |
| VBR (min) | 31.9 V @ 1 mA - Guaranteed avalanche initiation threshold; ensures reliable turn-on above normal operating voltage. |
| VC (max) | 45.4 V @ IPP = 13.2 A - Peak clamped voltage during 10/1000 µs surge; defines worst-case stress on downstream ICs. |
| PPK | 600 W @ 1 ms - Single-pulse surge handling capacity; validates robustness against IEC 61000-4-5 Level 4 events. |
| IR (max) | 5.0 µA @ 28 V - Reverse leakage at VRWM; low value minimizes standby power loss in battery-powered systems. |
| Response Time | <1.0 ns - Avalanche turn-on delay; critical for protecting high-speed logic and analog front-ends from nanosecond-scale transients. |
| UL Recognition | UL 497B QVGQ2 - Certified for isolated loop circuit protection; satisfies safety requirements for telecom and industrial field wiring. |
Pinout & Package
Package: SMB (Case 403A), surface-mount, void-free thermosetting plastic with modified L-bend leads and cathode polarity band. Dimensions: 4.32 mm × 2.13 mm × 2.26 mm (L × W × H).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Current sink during forward conduction; connected to protected line ground or low-side reference. | Provides return path for surge current; must be routed with minimal inductance to maintain clamping integrity. |
| Cathode | High-impedance input during normal operation; active clamping node during reverse transient. | Connected to the line being protected (e.g., +12 V rail); polarity band identifies this terminal for correct PCB placement. |
Key Features
| Feature | Design Value |
|---|---|
| 600 W Peak Pulse Power | Validated for single-event 10/1000 µs surges up to 13.2 A - enables use in harsh environments like automotive load-dump and industrial motor drive EMI. |
| UL 497B Certification | Recognized for isolated loop protector classification - eliminates need for additional safety validation in telecom and process control field wiring. |
| ESD Robustness | Class 3 (>16 kV HBM) - protects sensitive microcontrollers and interface ICs without external ESD staging. |
| Low Clamping Ratio | VC / VBR = 45.4 / 31.9 ≈ 1.42 - tight ratio ensures minimal overvoltage margin between breakdown and clamp, reducing stress on downstream components. |
| Pb-Free Construction | G-suffix variant meets RoHS Directive 2011/65/EU - supports lead-free reflow profiles and environmental compliance for global OEM shipments. |
Applications
| Automotive Power Input Protection | Industrial PLC Digital I/O Protection |
|---|---|
|
Use Scenario: 12 V battery-fed ECUs exposed to ISO 7637-2 pulse 1 (−150 V, 50 ms) and pulse 3a (±100 V, 150 ns). IC Role / Device Role / Timing Role: Unidirectional TVS placed at connector entry to clamp negative transients before they reach LDOs and CAN transceivers. Use Value: Limits voltage to ≤45.4 V during 13.2 A surge, preventing latch-up or gate oxide damage in 3.3 V/5 V logic supplies. |
Use Scenario: 24 V digital input modules receiving signals from field sensors in factory automation. IC Role / Device Role / Timing Role: Primary overvoltage clamp on dry-contact or optocoupler input lines subject to inductive kickback and EFT bursts. Use Value: Sub-1 ns response ensures clamping occurs before transient propagates into microcontroller GPIO, avoiding false triggering or reset. |
| Telecom Interface Surge Protection | Medical Equipment Power Rail Protection |
|
Use Scenario: RS-485/RS-232 ports in base station controllers subjected to lightning-induced common-mode surges. IC Role / Device Role / Timing Role: Line-side TVS on each signal conductor referenced to chassis ground, meeting ITU-T K.21 basic protection level. Use Value: UL 497B recognition confirms suitability for telecom isolation barrier applications without requiring supplemental creepage/clearance redesign. |
Use Scenario: Auxiliary 5 V/12 V rails in diagnostic imaging equipment where reliability and safety certification are mandatory. IC Role / Device Role / Timing Role: Secondary protection stage after primary MOV/fuse, suppressing fast transients missed by slower bulk suppressors. Use Value: Low leakage (<5 µA) avoids loading precision reference circuits; 150 °C max TJ supports operation inside sealed enclosures with limited airflow. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient voltage suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMBJ28A | Same VRWM (28 V), identical SMB package, but lower PPK (600 W same), higher VC (48.4 V vs. 45.4 V) at same IPP. | Marginally higher clamping voltage reduces protection margin for 3.3 V logic; acceptable where 48.4 V is within downstream IC absolute max ratings. | Select SMBJ28A only if legacy BOM alignment or second-source qualification requires Diodes Inc. footprint compatibility. |
| 1.5SMC28A | Higher PPK (1500 W), larger SMC package (7.11 mm × 6.22 mm), same VRWM and VBR range, VC = 45.7 V @ 32.8 A. | Over-spec'd surge capacity suits high-energy environments (e.g., railway traction control), but requires PCB layout change due to larger footprint. | Choose 1.5SMC28A when system-level surge testing exceeds IEC 61000-4-5 Level 4 and board space allows SMC mounting. |
Compared with SMBJ28A and 1.5SMC28A, the 1SMB28AT3 delivers optimal balance of compact SMB form factor, industry-leading clamping voltage (45.4 V), UL 497B certification, and proven field reliability in automotive and industrial deployments-making it the preferred choice for space-constrained, safety-certified designs.
Availability
1SMB28AT3 is available at Aetrix Electronics and suitable for automotive electronics, industrial PLCs, and telecom infrastructure requiring stable component supply with full traceability and long-term lifecycle support.
Supply support for 1SMB28AT3 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
ON Semiconductor (now onsemi) is a global semiconductor supplier specializing in energy-efficient power management, analog, sensor, and connectivity solutions for automotive, industrial, and cloud power applications.
The 1SMB28AT3 belongs to the SMB series of unidirectional TVS diodes engineered for high-reliability transient suppression in harsh electromagnetic environments-designed specifically for cost-sensitive, high-volume applications demanding UL certification and robust surge immunity.
FAQ
What is the maximum clamping voltage of the 1SMB28AT3 under standard surge conditions?
The 1SMB28AT3 has a maximum clamping voltage (VC) of 45.4 V when subjected to its rated peak pulse current (IPP) of 13.2 A, measured using the standardized 10/1000 µs double-exponential waveform. This value is guaranteed across temperature and represents the highest voltage seen by downstream circuitry during a worst-case transient event. The 1SMB28AT3 maintains this clamping performance while delivering 600 W peak power dissipation capability.
Does the 1SMB28AT3 meet UL safety standards for isolated loop protection?
Yes, the 1SMB28AT3 carries UL 497B recognition under file #E210057 in the "Protectors" category (QVGQ2), validating its suitability for isolated loop circuit protection in telecom and industrial field wiring. This certification covers rigorous testing including strike voltage breakdown, endurance conditioning, dielectric withstand, and discharge performance-going beyond basic flammability requirements. The 1SMB28AT3's UL 497B status is explicitly confirmed in the official ON Semiconductor datasheet Rev. 11.
What is the reverse leakage current specification for the 1SMB28AT3 at its working voltage?
The 1SMB28AT3 specifies a maximum reverse leakage current (IR) of 5.0 µA when biased at its working peak reverse voltage (VRWM) of 28 V, tested at TA = 25°C. This low leakage ensures minimal power loss in always-on systems such as battery-backed medical devices or remote IoT sensors. The 1SMB28AT3 maintains this IR limit across its full operating temperature range (−65°C to +150°C), supporting reliable performance in wide-temperature deployments.
Can the 1SMB28AT3 be used in bidirectional transient protection applications?
No, the 1SMB28AT3 is a unidirectional TVS diode and is not suitable for bidirectional protection. Its electrical characteristics-including breakdown voltage, clamping behavior, and polarity marking-are defined only for reverse-biased operation. For AC or dual-polarity signal lines (e.g., RS-485 differential pairs), a dedicated bidirectional part such as the 1SMB28CAT3 must be used. Using the 1SMB28AT3 in bidirectional configurations risks failure during positive half-cycle transients.
What is the thermal resistance from junction to lead (RJL) for the 1SMB28AT3, and why does it matter?
The 1SMB28AT3 has a thermal resistance from junction to lead (RJL) of 40 °C/W, measured under specified conditions (1 in² copper pad, FR-4 board). This parameter directly impacts sustained surge handling: lower RJL enables faster heat transfer from the silicon junction to the PCB copper, improving reliability during repetitive or high-duty-cycle transients. When designing layouts for the 1SMB28AT3, maximizing copper area connected to both anode and cathode pads is essential to realize this thermal performance.
1SMB28AT3 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Package/Case:
- DO-214AA, SMB
- Series:
- -
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Type:
- Zener
- Unidirectional Channels:
- 1
- Bidirectional Channels:
- -
- Voltage - Reverse Standoff (Typ):
- 28V
- Voltage - Breakdown (Min):
- 31.1V
- Voltage - Clamping (Max) @ Ipp:
- 45.4V
- Current - Peak Pulse (10/1000µs):
- 13.2A
- Power - Peak Pulse:
- 600W
- Power Line Protection:
- No
- Applications:
- General Purpose
- Capacitance @ Frequency:
- 590pF @ 1MHz
- Operating Temperature:
- -65°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SMB
1SMB28AT3 FAQ
1.How can I place an order for 1SMB28AT3 through Aetrix?
Please submit a Request for Quotation (RFQ) for 1SMB28AT3 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 1SMB28AT3 reliable?
The price and inventory of 1SMB28AT3 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 1SMB28AT3 is usually 5 days.
3.What payment methods are accepted for 1SMB28AT3?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 1SMB28AT3 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 1SMB28AT3?
1SMB28AT3 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 1SMB28AT3 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 1SMB28AT3?
For technical support, including 1SMB28AT3 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 1SMB28AT3 requirements.
6.How does Aetrix verify that 1SMB28AT3 is sourced from the original manufacturer or authorized distributors?
All 1SMB28AT3 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 1SMB28AT3 meets industry standards.
7.What is the process for return or replacement of 1SMB28AT3?
All 1SMB28AT3 units undergo pre-shipment inspection (PSI). If there is an issue with 1SMB28AT3, 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 1SMB28AT3 part is unused and in its original packaging.
Return procedure for 1SMB28AT3:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
1SMB28AT3 Tags
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