SMAJ28A-TR STMicroelectronics TVS Diode (Uni-directional) (Other) In Stock
The SMAJ28A-TR is a unidirectional 400 W transient voltage suppressor diode with a 28 V standoff voltage and 45.4 V maximum clamping voltage at peak pulse current. It is housed in a compact SMA 2-pin surface-mount package and provides fast response transient protection for sensitive electronics. This device is suited for protecting signal lines, I/O ports, and power supply rails from ESD and surge events.
- Manufacturer
- STMicroelectronics
- Package
- Other
- Pin Count
- 2
- Lifecycle
- ACTIVE
- Datasheet
- SMAJ28A-TR Datasheet PDF
- Category
- TVS Diode (Uni-directional)
- Price
- From $0.0547(MOQ 1)
- Temp Range
- -55.0°C to 150.0°C
- RoHS
- Compliant
- Lead Time
- 3–7 business days
- Shipping
- DHL Express · Worldwide
Key Features
- 28 V standoff voltage with 45.4 V maximum clamping voltage
- 400 W peak pulse power dissipation (10/1000 µs waveform)
- Unidirectional silicon TVS for positive transient suppression
- Fast response time below 1 ps for ESD protection
- Compact SMA surface-mount package for automated PCB assembly
- MOS-compatible for direct protection of CMOS I/O lines
- 31.1 V minimum breakdown voltage with tight voltage tolerance
Applications
The SMAJ28A-TR is widely used for ESD and surge protection on 24 V industrial I/O signal lines, RS-485 and CAN bus interfaces in factory automation equipment, and 28 V nominal power supply rails in aerospace and military electronics. It protects sensitive CMOS and MOSFET gate inputs from voltage transients exceeding 28 V that could otherwise cause latch-up or gate oxide damage. Automotive body electronics and truck lighting control modules operating on 24 V systems also rely on this device for robust overvoltage protection.
Specifications
| Reach Compliance Code | Not Compliant |
| Factory Lead Time | 13Weeks |
| YTEOL | 6 |
| Additional Feature | MOS COMPATIBLE |
| Breakdown Voltage-Min | 31.1V |
| Breakdown Voltage-Nom | 32.7V |
| Clamping Voltage-Max | 45.4V |
| Configuration | SINGLE, 1 CHANNEL |
| Diode Element Material | SILICON |
| Diode Type | TRANS VOLTAGE SUPPRESSOR DIODE |
| JEDEC-95 Code | DO-214AC |
| JESD-30 Code | R-PDSO-C2 |
| JESD-609 Code | e3 |
| Non-rep Peak Rev Power Dis-Max | 400W |
| Number of Elements | 1 |
| Package Body Material | PLASTIC/EPOXY |
| Package Shape | RECTANGULAR |
| Package Style | SMALL OUTLINE |
| Peak Reflow Temperature (Cel) | 260 |
| Polarity | UNIDIRECTIONAL |
| Power Dissipation-Max | 3.3W |
| Qualification Status | Not Qualified |
| Reference Standard | IEC-61000-4-2, 4-4, 4-5; MIL-STD-750 |
| Rep Pk Reverse Voltage-Max | 28V |
| Reverse Current-Max | 2 µA |
| Reverse Test Voltage | 28V |
| Surface Mount | YES |
| Technology | AVALANCHE |
| Terminal Finish | Matte Tin (Sn) - annealed |
| Terminal Form | C BEND |
| Terminal Position | DUAL |
| Package | Other |
Compliance & Regulatory
| RoHS Status | Compliant |
| Lead-Free | Yes (Pb-Free) |
| Moisture Sensitivity Level | MSL 1 |
| ECCN | EAR99 |
| HTS Code | 8541.10.00.50 |
| Country of Origin | Mainland China |
Alternate & Equivalent Parts
No known alternates. Submit an RFQ and our team can suggest alternatives.
Frequently Asked Questions
What clamping voltage does SMAJ28A-TR maintain during a 400 W surge pulse?
During a peak pulse of 400 W applied as a 10/1000 µs surge waveform, the SMAJ28A-TR clamps the protected line to a maximum of 45.4 V at the corresponding peak pulse current. This ensures downstream circuits rated at 60 V or higher are fully protected against transients on a 28 V nominal bus. The nominal clamping voltage at 1 mA reverse current is approximately 32.7 V.
How does the SMAJ28A-TR protect CMOS I/O lines in a 24 V industrial controller?
Placed in parallel with the I/O signal line between the line and ground, the SMAJ28A-TR remains reverse-biased during normal 24 V operation and only conducts when a positive transient exceeds its 28 V standoff voltage. Its sub-picosecond response time ensures ESD pulses following IEC 61000-4-2 waveforms are clamped before reaching CMOS input protection structures, preventing gate oxide breakdown in process controllers and PLCs operating at 24 V logic levels.
In which package does SMAJ28A-TR ship, and how does it fit on a standard SMD footprint?
The SMAJ28A-TR is housed in the SMA (DO-214AC) 2-pin surface-mount package, measuring approximately 4.4 mm x 2.7 mm with a 2.3 mm body height. This package is compatible with standard 0805-scale SMD land patterns on two-layer FR4 PCBs and is handled by standard pick-and-place equipment. The -TR suffix indicates tape-and-reel packaging in 3000-unit reels for high-volume automated assembly.
Can SMAJ28A-TR replace SMAJ28CA for bidirectional AC line protection?
No, the SMAJ28A-TR is a unidirectional TVS and conducts only for positive transients above its 28 V standoff threshold, with forward conduction for negative transients above 1.2 V like a standard rectifier diode. For AC lines or differential signals subject to both positive and negative transients, the bidirectional SMAJ28CA variant should be used instead, as it provides symmetric clamping at ±45.4 V for the same 400 W peak pulse rating.
What is the maximum continuous reverse standoff voltage for SMAJ28A-TR and why does it matter for selection?
The SMAJ28A-TR has a maximum reverse standoff voltage (VRWM) of 28 V, meaning it remains non-conducting at any DC bias below 28 V. Selecting a TVS with a standoff voltage above the circuit's maximum operating voltage—here at least 28 V for a 24 V nominal rail with 15% tolerance headroom—prevents false triggering during normal operation, which would cause unwanted current draw, excessive power dissipation, and potential destruction of the device.
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| Qty. | Unit Price | Ext. Price |
|---|---|---|
| 1+ | $0.1500 | $0.15 |
| 5000+ | $0.1010 | $505.00 |
| 20000+ | $0.0574 | $1148.40 |
| 40000+ | $0.0561 | $2242.00 |
| 80000+ | $0.0547 | $4379.20 |
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