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onsemi 1SMA28AT3
- Part No.:
- 1SMA28AT3
- Manufacturer:
- onsemi
- Category:
- TVS Diodes
- Package:
- DO-214AC, SMA
- Datasheet:
-
1SMA28AT3.pdf
- Description:
- TVS DIODE 28VWM 45.4VC SMA
- Quantity:
- Payment:
- Shipping:
Inventory:2,092
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Product details
Overview
1SMA28AT3 from ON Semiconductor is a unidirectional 400 W peak power Zener transient voltage suppressor (TVS) designed for clamping high-energy transients in DC power lines and signal paths. It features a 28 V working peak reverse voltage (VRWM), 32.75 V nominal breakdown voltage (VBR) at 1 A test current, 45.4 A maximum peak pulse current (IPP), and clamps to ≤45.4 V at that current. It is used in automotive power supply protection and industrial control I/O interfaces.
For engineers reviewing the 1SMA28AT3 datasheet, pinout, applications, or equivalent options, key selection criteria include VRWM ≥ system operating voltage, clamping voltage margin relative to protected IC absolute maximum ratings, surge current capability under 10/1000 µs waveform, and SMA package thermal performance on FR-4 PCBs.
Technical Context
The 1SMA28AT3 operates as a unidirectional avalanche diode, conducting only during negative transients relative to its anode–cathode orientation. Its clamping action begins at VRWM = 28 V and fully engages at VBR = 32.75 V (min) with IT = 1 A, delivering VC ≤ 45.4 V at IPP = 45.4 A under 10/1000 µs pulse conditions.
It exhibits low zener impedance and sub-1 ns response time, enabling effective suppression of ESD (Class 3, >16 kV HBM) and lightning-induced surges. The device is rated for TJ = −65 °C to +150 °C and requires no bias circuitry-functioning passively in series with protected lines or across rails.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VRWM | 28 V - Maximum continuous reverse voltage before significant leakage; must exceed normal operating voltage of protected circuit. |
| VBR (min/typ/max) | 31.1 / 32.75 / 34.4 V @ IT = 1 A - Confirms reliable avalanche onset within defined tolerance band for predictable clamping threshold. |
| VC @ IPP | ≤45.4 V @ 45.4 A - Clamping voltage under worst-case 400 W surge; determines maximum stress on downstream components. |
| PPK | 400 W @ 1 ms - Peak transient energy handling per non-repetitive 10/1000 µs pulse; defines single-event robustness. |
| IR @ VRWM | ≤2.5 µA - Reverse leakage at stand-off voltage; ensures minimal power loss and signal integrity in standby. |
| ESD Rating | Class 3 (>16 kV HBM) - Validated human-body-model ESD immunity; qualifies for harsh-environment interface protection. |
| Response Time | <1 ns - Enables suppression of fast-rising transients before sensitive logic or analog circuitry is damaged. |
Pinout & Package
The 1SMA28AT3 is housed in an SMA (DO-214AC) surface-mount plastic package (Case 403D-02), featuring a low-profile, flat handling surface optimized for automated placement and top- or bottom-side PCB mounting. Polarity is marked by a cathode band.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Current entry terminal during forward conduction; connected to lower-potential side of protected line. | Provides low-VF path (<3.5 V @ 30 A) for fault currents when TVS is forward-biased during negative transients. |
| Cathode | Current exit terminal during reverse avalanche; connected to higher-potential side (e.g., VCC rail or signal line). | Defines polarity-sensitive clamping direction; cathode band must align with PCB silkscreen marking for correct installation. |
Key Features
| Feature | Design Value |
|---|---|
| 400 W peak pulse power | Enables robust protection against IEC 61000-4-5 Level 4 surges (4 kV line-to-ground) without derating on standard FR-4 layouts. |
| Low zener impedance | Minimizes voltage overshoot during high di/dt events, maintaining clamping accuracy under fast-rising transients. |
| Flat handling surface | Ensures consistent pick-and-place yield and coplanarity during reflow, critical for automated SMT assembly. |
| Pb-free (1SMA28AT3G) option | Meets RoHS Directive 2011/65/EU and JEDEC J-STD-020 moisture sensitivity level (MSL) requirements. |
| −65 °C to +150 °C operation | Supports deployment in under-hood automotive ECUs and industrial motor drives with wide ambient temperature swings. |
Applications
| Automotive Power Rail Protection | Industrial PLC Digital Input Protection |
|---|---|
Use Scenario: Suppresses load-dump spikes (up to 120 V, 400 ms) and alternator ripple on 12 V battery-fed ECUs. IC Role / Device Role / Timing Role: Unidirectional TVS placed between battery rail and local regulator input to clamp overvoltage before LDO damage. Use Value: Limits rail voltage to ≤45.4 V during 45.4 A surge, protecting 40 V-rated input capacitors and regulators. | Use Scenario: Shields 24 V digital input channels in programmable logic controllers from field-wiring induced transients. IC Role / Device Role / Timing Role: Standoff device mounted across input terminals to shunt surge energy away from optocoupler input LED and series resistor. Use Value: Maintains <2.5 µA leakage at 24 V nominal, preserving input threshold accuracy while clamping 1 kV/0.5 A transients. |
| Medical Equipment ESD Interface Protection | Telecom Line Card Surge Suppression |
Use Scenario: Guards RS-232/USB ports on diagnostic imaging systems against operator ESD events (>15 kV contact discharge). IC Role / Device Role / Timing Role: Primary-level TVS on connector side of ESD protection network, preceding TVS arrays and filtering. Use Value: Responds in <1 ns to divert >16 kV HBM energy, preventing latch-up in UART transceivers with 3.3 V I/O. | Use Scenario: Protects Ethernet PHY power pins and data lines in carrier-grade access switches from lightning-induced surges. IC Role / Device Role / Timing Role: Secondary-stage clamping device after gas discharge tube (GDT), limiting let-through voltage to PHY ICs. Use Value: Delivers 400 W peak dissipation with 45.4 V clamping, compatible with IEEE 802.3af PoE voltage margins. |
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), but 600 W PPK rating and SMB package (larger footprint, lower RJA). | Higher surge margin for IEC 61000-4-5 Level 5 testing; requires PCB layout change due to larger case size. | Select when 600 W surge headroom is required and board space permits SMB footprint. |
| 1.5SMC28A | Same VRWM (28 V), 1500 W PPK, DO-214AB package; higher VF (3.5 V max @ 30 A same as 1SMA28AT3). | Designed for chassis-level primary protection; not suitable for board-level point-of-load clamping due to slower response. | Choose for upstream bulk suppression where clamping speed is secondary to energy absorption. |
Compared with SMBJ28A and 1.5SMC28A, the 1SMA28AT3 offers optimal balance of 400 W surge capability, compact SMA footprint, and sub-1 ns response-making it ideal for space-constrained, high-speed point-of-load protection where moderate energy levels dominate.
Availability
1SMA28AT3 is available at Aetrix Electronics and suitable for automotive power rail protection, industrial PLC digital input protection, and medical equipment ESD interface protection requiring stable component supply and full traceability.
Supply support for 1SMA28AT3 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 is a global semiconductor manufacturer specializing in power management, analog, sensor, and discrete devices for automotive, industrial, and communications markets.
The 1SMA28AT3 belongs to ON Semiconductor's SMA-series transient voltage suppressors-a family engineered for cost-effective, high-reliability overvoltage protection in space-limited surface-mount applications.
FAQ
What is the maximum clamping voltage of the 1SMA28AT3 under surge conditions?
The 1SMA28AT3 has a maximum clamping voltage (VC) of 45.4 V when subjected to its rated peak pulse current (IPP) of 45.4 A under the standardized 10/1000 µs waveform. This value is measured at TJ = 25°C and defines the upper voltage limit imposed on protected circuitry during a worst-case transient event. The 1SMA28AT3 maintains this clamping performance consistently across its qualified temperature range.
Is the 1SMA28AT3 suitable for bidirectional transient suppression?
No, the 1SMA28AT3 is a unidirectional TVS diode and conducts only in reverse avalanche mode-intended for DC rail or polarized signal line protection. For bidirectional applications such as AC lines or differential data buses, ON Semiconductor offers the 1SMA28CAT3 variant. Using the 1SMA28AT3 in bidirectional configurations may result in forward conduction damage during negative half-cycles.
What is the thermal resistance from junction to ambient (RJA) for the 1SMA28AT3?
The 1SMA28AT3 has a thermal resistance from junction to ambient (RJA) of 250 °C/W when mounted on an FR-4 PCB using ON Semiconductor's minimum recommended footprint (Case 403D-02 outline). This value assumes TA = 25°C and governs steady-state power derating; the device's 0.5 W DC power dissipation rating is derived directly from this RJA and its maximum junction temperature limit of +150°C.
Does the 1SMA28AT3 meet RoHS requirements?
Yes-the 1SMA28AT3 is available in a Pb-free version designated as 1SMA28AT3G, which complies with the EU RoHS Directive 2011/65/EU. The "G" suffix indicates lead-free terminations and halogen-free molding compound. Standard 1SMA28AT3 units are also RoHS-compliant per ON Semiconductor's product stewardship policy, with full material declarations available upon request.
How does the 1SMA28AT3 compare to the 1SMA24AT3 in terms of voltage rating and application scope?
The 1SMA28AT3 has a higher working peak reverse voltage (VRWM = 28 V) than the 1SMA24AT3 (VRWM = 24 V), making it suitable for 24 V nominal systems with wider voltage tolerances or higher transient margins. Its VBR (32.75 V typ) and VC (45.4 V) are correspondingly elevated, providing greater headroom before clamping engages-ideal for automotive 12 V/24 V dual-voltage platforms where load dump peaks exceed 30 V. The 1SMA28AT3 retains identical package, surge rating, and thermal specs.
1SMA28AT3 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Package/Case:
- DO-214AC, SMA
- 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):
- 8.8A
- Power - Peak Pulse:
- 400W
- Power Line Protection:
- No
- Applications:
- General Purpose
- Capacitance @ Frequency:
- 430pF @ 1MHz
- Operating Temperature:
- -65°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SMA
1SMA28AT3 FAQ
1.How can I place an order for 1SMA28AT3 through Aetrix?
Please submit a Request for Quotation (RFQ) for 1SMA28AT3 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 1SMA28AT3 reliable?
The price and inventory of 1SMA28AT3 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 1SMA28AT3 is usually 5 days.
3.What payment methods are accepted for 1SMA28AT3?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 1SMA28AT3 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 1SMA28AT3?
1SMA28AT3 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 1SMA28AT3 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 1SMA28AT3?
For technical support, including 1SMA28AT3 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 1SMA28AT3 requirements.
6.How does Aetrix verify that 1SMA28AT3 is sourced from the original manufacturer or authorized distributors?
All 1SMA28AT3 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 1SMA28AT3 meets industry standards.
7.What is the process for return or replacement of 1SMA28AT3?
All 1SMA28AT3 units undergo pre-shipment inspection (PSI). If there is an issue with 1SMA28AT3, 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 1SMA28AT3 part is unused and in its original packaging.
Return procedure for 1SMA28AT3:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
1SMA28AT3 Tags
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