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Vishay General Semiconductor - Diodes Division SMAJ28AHM3/H
- Part No.:
- SMAJ28AHM3/H
- Manufacturer:
- Vishay General Semiconductor - Diodes Division
- Category:
- TVS Diodes
- Package:
- DO-214AC, SMA
- Datasheet:
-
SMAJ28AHM3/H.pdf
- Description:
- TVS DIODE 28VWM 45.4VC DO214AC
- Quantity:
- Payment:
- Shipping:
Inventory:7,682
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Product details
Overview
SMAJ28AHM3/H from Vishay General Semiconductor is a unidirectional surface-mount Transient Voltage Suppressor (TVS) diode in SMA (DO-214AC) package, designed for clamping voltage transients on power and signal lines. It features a 28 V stand-off voltage (VWM), 31.1–34.4 V breakdown voltage (VBR) at 1 mA, 45.4 V maximum clamping voltage (VC) at 8.8 A peak pulse current (IPPM), and 400 W peak pulse power (10/1000 μs waveform). It is widely used to protect MOSFETs, ICs, and sensor interfaces in automotive and industrial power supplies.
For engineers reviewing the SMAJ28AHM3/H datasheet, SMAJ28AHM3/H pinout, SMAJ28AHM3/H application, or SMAJ28AHM3/H equivalent, key selection criteria include its AEC-Q101 qualification status, halogen-free RoHS-compliant construction (HM3 suffix), low thermal resistance (RθJL = 30 °C/W), and suitability for high-reliability 12 V/24 V DC bus protection where fast response (<1 ns), low clamping ratio (VC/VBR ≈ 1.43), and surge robustness (IFSM = 40 A) are critical.
Technical Context
The SMAJ28AHM3/H operates as a unidirectional avalanche diode, conducting only when reverse voltage exceeds its breakdown threshold. Its glass-passivated junction ensures stable VBR tolerance (±5 %) and low leakage (ID ≤ 1.0 μA at 28 V), while the SMA package enables automated placement and meets MSL level 1 reflow requirements (peak 260 °C).
It delivers 400 W transient suppression capability under standard 10/1000 μs waveform conditions, derating to 300 W above 78 V - though SMAJ28AHM3/H remains fully rated at 400 W. Its clamping performance is validated with 45.4 V VC at 8.8 A IPPM, yielding a clamping ratio of 1.43 relative to nominal VBR (32.75 V avg), supporting reliable overvoltage margin design for 3.3 V–24 V logic and power rails.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VWM | 28 V - Maximum continuous reverse operating voltage before significant leakage; defines upper limit for safe DC bias in protected circuits. |
| VBR min/max | 31.1 V / 34.4 V at IT = 1 mA - Confirmed breakdown range ensures predictable turn-on across temperature and unit variation. |
| VC @ IPPM | 45.4 V at 8.8 A - Clamping voltage during 10/1000 μs surge; determines worst-case overvoltage seen by downstream components. |
| PPPM | 400 W (10/1000 μs) - Peak transient energy handling capacity; supports repeated surge events in automotive load-dump and inductive switching environments. |
| ID @ VWM | ≤ 1.0 μA - Ultra-low reverse leakage preserves battery life and signal integrity in always-on sensor or control circuits. |
| TJ max | +150 °C - Enables operation in under-hood automotive and industrial enclosures without derating at ambient up to +125 °C. |
| AEC-Q101 | Qualified - Validated for automotive-grade reliability including temperature cycling, HTRB, and ESD per AEC-Q101 Rev G. |
Pinout & Package
Package: SMA (DO-214AC), surface-mount, low-profile case with matte tin-plated leads solderable per J-STD-002 and JESD 22-B102. Cathode indicated by band marking on unidirectional device.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Forward conduction terminal | Connected to lower-potential side (e.g., ground or return path); conducts during forward surge or bias conditions. |
| Cathode | Reverse-biased clamping terminal | Connected to protected line (e.g., 24 V rail); avalanches into conduction when transient exceeds VBR, shunting surge current to ground. |
Key Features
| Feature | Design Value |
|---|---|
| AEC-Q101 qualified (HM3 suffix) | Validated for automotive applications including engine control units, body electronics, and ADAS power domains. |
| Halogen-free & RoHS-compliant | Meets IEC 61249-2-21 and JEDEC J-STD-020 MSL level 1, enabling lead-free reflow compatibility and environmental compliance. |
| 400 W peak pulse power (10/1000 μs) | Supports EN 61000-4-5 Level 4 (4 kV) surge immunity testing on 50 Ω source impedance without degradation. |
| Low clamping ratio (VC/VBR ≈ 1.43) | Minimizes overvoltage stress on downstream ICs such as CAN transceivers or microcontrollers with 36 V absolute max ratings. |
| Fast response time (< 1 ns) | Clamps transients before propagation into sensitive analog or digital circuitry, preserving signal fidelity in high-speed sensor interfaces. |
Applications
| Automotive Power Rail Protection | Industrial Sensor Interface Protection |
|---|---|
|
Use Scenario: Protecting 24 V supply lines in vehicle ECUs against ISO 7637-2 pulse 1 (inductive switch-off) and pulse 3a/b (load dump). IC Role / Device Role / Timing Role: Unidirectional TVS placed between 24 V rail and chassis ground, acting as last-line clamping element after upstream filters. Use Value: Limits transient overshoot to ≤45.4 V, ensuring survival of 36 V-rated power management ICs and preventing latch-up in connected microcontrollers. |
Use Scenario: Shielding analog output lines (e.g., 4–20 mA current loop) of pressure or temperature sensors in factory automation systems. IC Role / Device Role / Timing Role: Bidirectional clamping is not required; SMAJ28AHM3/H provides targeted reverse-polarity and surge protection on powered sensor outputs. Use Value: Suppresses ESD and switching noise from nearby solenoids without adding capacitance (>100 pF), preserving loop accuracy and bandwidth. |
| DC-DC Converter Input Protection | Motor Drive Gate Driver Supply Clamp |
|
Use Scenario: Safeguarding input stage of 24 V-to-5 V buck converters in robotics controllers exposed to back-EMF from brushed DC motors. IC Role / Device Role / Timing Role: Placed directly at converter input capacitor, absorbing repetitive 100–500 V/μs transients before they reach controller IC. Use Value: Withstands ≥1000 surges at 400 W rating and maintains VBR stability over 1000+ thermal cycles due to glass passivation. |
Use Scenario: Clamping auxiliary 15 V gate driver supply in half-bridge motor drivers subject to shoot-through-induced voltage spikes. IC Role / Device Role / Timing Role: Connected between gate driver VDD and GND, limiting supply rail excursions during fault conditions. Use Value: Fast <1 ns response prevents overvoltage damage to isolated gate drivers (e.g., Si823x), while 40 A IFSM handles single-event overcurrent. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient voltage suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMAJ28AHE3/H | Same electrical specs, but RoHS-compliant commercial grade (E3) without halogen-free certification; no AEC-Q101 qualification. | Approved for non-automotive industrial and consumer use only; not suitable for automotive OEM or Tier 1 designs requiring AEC-Q101. | Select SMAJ28AHE3/H only if halogen-free content and automotive qualification are not required, and cost optimization is prioritized. |
| SMBJ28A-H | Higher 600 W PPPM rating, larger SMB (DO-214AA) package, RθJA = 85 °C/W vs. 120 °C/W, same VWM/VBR/VC specs. | Better thermal performance and surge margin; requires larger PCB footprint and may not fit space-constrained layouts. | Choose SMBJ28A-H when higher surge endurance (e.g., ISO 16750-2 12 V load dump) is needed and board area allows SMB footprint. |
Compared with SMAJ28AHM3/H, SMAJ28AHE3/H lacks halogen-free and AEC-Q101 validation, while SMBJ28A-H trades compact size for enhanced thermal and surge capability - making SMAJ28AHM3/H optimal for space-limited, automotive-qualified 24 V rail protection where footprint and compliance are decisive.
Availability
SMAJ28AHM3/H is available at Aetrix Electronics and suitable for automotive electronic control units, industrial sensor modules, and DC-DC converter input stages requiring stable component supply, long-term lifecycle support, and AEC-Q101 traceability.
Supply support for SMAJ28AHM3/H 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
Vishay General Semiconductor is a global leader in discrete semiconductors, specializing in diodes, rectifiers, MOSFETs, and protection devices with emphasis on reliability, efficiency, and application-specific optimization.
The SMAJ series was developed for high-reliability transient suppression in harsh environments - particularly automotive and industrial systems - where consistent clamping, low leakage, and AEC-Q101 validation are mandatory.
FAQ
What is the meaning of the 'HM3' suffix in SMAJ28AHM3/H?
The 'HM3' suffix in SMAJ28AHM3/H indicates halogen-free, RoHS-compliant construction and AEC-Q101 qualification. It confirms compliance with JEDEC J-STD-020 MSL level 1, matte tin plating per J-STD-002, and full automotive reliability testing - distinguishing it from commercial-grade E3 variants. This makes SMAJ28AHM3/H suitable for under-hood and safety-critical automotive applications where material content and qualification are audited.
Does SMAJ28AHM3/H support bidirectional transient suppression?
No, SMAJ28AHM3/H is a unidirectional TVS diode - it clamps only in reverse bias and conducts forward current like a standard diode. Its cathode band marks the clamping terminal. For bidirectional protection, Vishay offers the SMAJ28CA variant. Using SMAJ28AHM3/H in bidirectional configurations risks forward conduction during negative transients and inadequate clamping, so SMAJ28AHM3/H must be applied with correct polarity in DC systems.
What is the maximum clamping voltage of SMAJ28AHM3/H under surge conditions?
The maximum clamping voltage (VC) of SMAJ28AHM3/H is 45.4 V at 8.8 A peak pulse current (IPPM), tested with a 10/1000 μs waveform. This value is guaranteed across temperature and process variation, and defines the highest voltage that will appear across the protected line during a standardized surge event - critical for verifying margin against downstream IC absolute maximum ratings.
Can SMAJ28AHM3/H be used in 12 V automotive systems?
Yes, SMAJ28AHM3/H is commonly deployed in 12 V automotive systems - especially for protecting 12 V battery-fed circuits against load dump (ISO 16750-2) and inductive switching transients. Its 28 V stand-off voltage provides sufficient margin above nominal 12 V (with tolerance), while its 45.4 V clamping voltage stays well below the 60 V absolute maximum rating of most automotive power ICs, making SMAJ28AHM3/H a robust choice for this voltage class.
How does the thermal resistance of SMAJ28AHM3/H affect PCB layout?
SMAJ28AHM3/H has a typical junction-to-lead thermal resistance (RθJL) of 30 °C/W and junction-to-ambient (RθJA) of 120 °C/W on 0.2" × 0.2" copper pads. To maintain reliability under repetitive surges, PCB layout must provide adequate copper area at both terminals - minimum 5.0 mm × 5.0 mm per pad - and avoid narrow traces. Poor thermal design risks localized overheating and premature failure, especially in high-duty-cycle industrial applications using SMAJ28AHM3/H.
SMAJ28AHM3/H Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Vishay General Semiconductor - Diodes Division
- Package/Case:
- DO-214AC, SMA
- Series:
- TransZorb®
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Discontinued at Digi-Key
- 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:
- Telecom
- Capacitance @ Frequency:
- -
- Operating Temperature:
- -55°C ~ 150°C (TJ)
- Grade:
- Automotive
- Qualification:
- AEC-Q101
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- DO-214AC (SMA)
SMAJ28AHM3/H FAQ
1.How can I place an order for SMAJ28AHM3/H through Aetrix?
Please submit a Request for Quotation (RFQ) for SMAJ28AHM3/H 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 SMAJ28AHM3/H reliable?
The price and inventory of SMAJ28AHM3/H are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMAJ28AHM3/H is usually 5 days.
3.What payment methods are accepted for SMAJ28AHM3/H?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMAJ28AHM3/H transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMAJ28AHM3/H?
SMAJ28AHM3/H orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMAJ28AHM3/H 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 SMAJ28AHM3/H?
For technical support, including SMAJ28AHM3/H datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMAJ28AHM3/H requirements.
6.How does Aetrix verify that SMAJ28AHM3/H is sourced from the original manufacturer or authorized distributors?
All SMAJ28AHM3/H 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 SMAJ28AHM3/H meets industry standards.
7.What is the process for return or replacement of SMAJ28AHM3/H?
All SMAJ28AHM3/H units undergo pre-shipment inspection (PSI). If there is an issue with SMAJ28AHM3/H, 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 SMAJ28AHM3/H part is unused and in its original packaging.
Return procedure for SMAJ28AHM3/H:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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