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STMicroelectronics SMAJ40A-TR
- Part No.:
- SMAJ40A-TR
- Manufacturer:
- STMicroelectronics
- Category:
- TVS Diodes
- Package:
- DO-214AC, SMA
- Datasheet:
-
SMAJ40A-TR.pdf
- Description:
- TVS DIODE 40VWM 84VC SMA
- Quantity:
- Payment:
- Shipping:
Inventory:13,633
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Product details
Overview
SMAJ40A-TR from STMicroelectronics is a unidirectional 400 W transient voltage suppression (TVS) diode in SMA package, designed for IEC 61000-4-2 ESD protection (30 kV air/contact) and IEC 61000-4-4 surge immunity (4 kV), with 40 V standoff voltage, 64.5 V clamping voltage at 6.2 A, and 0.2 µA leakage at 25 °C. It protects power rails and signal lines in industrial power supplies and automotive body electronics.
For engineers reviewing the SMAJ40A-TR datasheet, SMAJ40A-TR pinout, SMAJ40A-TR application, or SMAJ40A-TR equivalent, key selection criteria include clamping voltage under 8/20 µs surge, junction temperature derating above 25 °C, dynamic resistance (2.49 Ω), and compliance with IPC7531 footprint and JEDEC DO-214AC outline.
Technical Context
This TVS diode uses planar silicon technology to achieve low leakage current (0.2 µA @ 25 °C) and high junction temperature capability (Tj max = 150 °C), enabling long-term reliability in thermally constrained PCB layouts. Its unidirectional configuration provides asymmetric clamping-forward conduction only during negative transients-making it suitable for DC-biased lines like 40 V battery inputs or 3.3 V/5 V rail protection with ground-referenced surges.
The device's electrical behavior is defined by three core parameters: breakdown voltage (44.4–46.7 V at 1 mA), clamping voltage (64.5 V at 6.2 A, 10/1000 µs), and dynamic resistance (2.49 Ω), which collectively determine energy absorption linearity and voltage overshoot during fast transients. Thermal impedance is optimized via the SMA package's copper pad layout per IPC7531.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Standoff Voltage (VRM) | 40 V - Maximum continuous reverse operating voltage before breakdown begins. |
| Breakdown Voltage (VBR) | 44.4–46.7 V at 1 mA - Confirmed threshold where avalanche conduction initiates reliably. |
| Clamping Voltage (VCL) | 64.5 V at 6.2 A (10/1000 µs) - Peak voltage seen by protected circuit during rated surge event. |
| Peak Pulse Power (PPP) | 400 W (10/1000 µs) - Sustained surge energy handling capacity at ambient temperature. |
| Leakage Current (IRM) | 0.2 µA at 25 °C - Minimal DC loading on sensitive analog or low-power logic inputs. |
| Dynamic Resistance (RD) | 2.49 Ω - Slope of V-I curve in avalanche region; determines voltage rise per additional surge current. |
| Junction Temperature Range | −55 to +150 °C - Enables operation in under-hood automotive or industrial motor drive environments. |
Pinout & Package
The SMAJ40A-TR is housed in a JEDEC DO-214AC (SMA) surface-mount package with two terminals: cathode (marked band) and anode. The package complies with IPC7531 footprint standards and supports reflow soldering per J-STD-020 MSL level 1.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Cathode (banded end) | Surge return path | Connected to system ground or low-impedance reference; conducts avalanche current during positive transients. |
| Anode | Protected line connection | Connected to the line being protected (e.g., 40 V supply rail); blocks reverse current until breakdown threshold is exceeded. |
Key Features
| Feature | Design Value |
|---|---|
| IEC 61000-4-2 ESD immunity | 30 kV air discharge and 30 kV contact discharge - exceeds Level 4 for robust human-body model protection. |
| IEC 61000-4-4 surge immunity | 4 kV (Level 4) - withstands repetitive fast-rise ring-wave transients in industrial AC/DC power inputs. |
| Low leakage at elevated temperature | 1 µA at 85 °C - ensures minimal standby current drain in battery-backed systems. |
| Planar silicon construction | Enables stable VBR and RD over lifetime - critical for automotive and industrial applications requiring >10-year field reliability. |
| Matte tin-plated leads | Complies with JESD 22-B102 E3 and MIL-STD-750 Method 2026 - ensures solderability and whisker resistance in high-reliability assemblies. |
Applications
| Industrial Power Supply Input Protection | Automotive Body Control Module (BCM) Power Rail |
|---|---|
Use Scenario: 40 V DC input stage of DIN-rail power supply exposed to load dump and ISO 7637-2 pulses. IC Role / Device Role / Timing Role: Unidirectional TVS placed between input rail and chassis ground to clamp positive transients within 1 ns. Use Value: Clamps to 64.5 V at 6.2 A, preventing MOSFET gate oxide failure and maintaining downstream regulator input integrity. | Use Scenario: 12 V/40 V dual-rail BCM module powering door locks, lighting, and sensors in passenger compartment. IC Role / Device Role / Timing Role: Standoff-rated TVS on 40 V auxiliary rail to suppress ESD from user interface buttons and relay coil flyback. Use Value: 0.2 µA leakage preserves sleep-mode current budget; 150 °C Tj rating supports under-dash mounting near HVAC ducts. |
| Telecom Remote Radio Unit (RRU) DC Feed Line | Smart Grid Distribution Automation Terminal |
Use Scenario: 48 V PoE-like DC feed line delivering power and data to outdoor RRU units subject to lightning-induced surges. IC Role / Device Role / Timing Role: First-stage TVS on DC input before DC-DC converter, coordinated with upstream GDT and downstream ceramic capacitor. Use Value: 400 W peak pulse power handles induced surges up to 6.2 A without thermal runaway; DO-214AC package enables automated placement. | Use Scenario: 40 V backup battery input in distribution automation terminal installed in utility substations. IC Role / Device Role / Timing Role: Unidirectional clamping device protecting supercapacitor charging circuitry from grid switching transients. Use Value: 2.49 Ω dynamic resistance limits voltage overshoot during 8/20 µs surges, preserving supercapacitor voltage rating margin. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar unidirectional TVS diode applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMAJ40A from Vishay (SMCJ40A) | Same DO-214AC package, but 65.8 V clamping at 6.1 A (10/1000 µs); 2.7 Ω RD. | Slightly higher clamping increases risk of downstream overvoltage in tight-margin 40 V systems. | Prefer SMAJ40A-TR when clamping voltage headroom is ≤0.5 V below next-stage IC absolute maximum rating. |
| P6SMB40A from ON Semiconductor | DO-214AA package (slightly larger footprint); 64.5 V clamping at 6.2 A, but 3.1 Ω RD and 0.5 µA leakage at 25 °C. | Higher RD degrades clamping linearity; larger footprint may conflict with dense PCB layouts. | Select SMAJ40A-TR for space-constrained designs requiring lowest possible leakage and best thermal performance. |
Compared with SMAJ40A-TR, the Vishay SMCJ40A offers identical power rating but looser clamping control, while the ON Semiconductor P6SMB40A trades package compatibility and leakage performance for broader distributor availability-making SMAJ40A-TR optimal for thermally demanding, low-leakage 40 V rail protection.
Availability
SMAJ40A-TR is available at Aetrix Electronics and suitable for industrial power supplies, automotive body control modules, telecom remote radio units, and smart grid distribution terminals requiring stable component supply across extended temperature and surge stress conditions.
Supply support for SMAJ40A-TR 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
STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, specializing in power management, automotive ICs, and discrete protection devices with vertical manufacturing and AEC-Q101 qualification capabilities.
The SMAJ series belongs to ST's transient protection product line, engineered specifically for high-reliability ESD and surge suppression in harsh-environment applications where low leakage, high Tj, and precise clamping are mandatory.
FAQ
What is the maximum clamping voltage of SMAJ40A-TR under a 10/1000 µs surge?
The maximum clamping voltage is 64.5 V at 6.2 A for a 10/1000 µs waveform, measured at 25 °C ambient. This value increases with junction temperature due to the 10.1 × 10⁻⁴/°C temperature coefficient (αT), reaching approximately 67.2 V at 125 °C junction temperature.
Can SMAJ40A-TR be used in bidirectional signal line protection?
No - SMAJ40A-TR is unidirectional and only clamps positive transients relative to ground. For bidirectional protection (e.g., RS-485, USB D+/D−), the SMAJ40CA variant must be used, which provides symmetrical clamping for both polarities.
Does SMAJ40A-TR meet automotive AEC-Q101 requirements?
No - while SMAJ40A-TR operates up to 150 °C junction temperature and passes JESD22-A108 thermal cycling, it is not AEC-Q101 qualified. For automotive-grade TVS diodes, ST recommends the Automotive Qualified SMAJ40A-Q, which includes full stress testing per AEC-Q101 Rev H.
How does the dynamic resistance affect system-level surge protection design?
With a measured RD of 2.49 Ω, SMAJ40A-TR adds predictable voltage rise (ΔV = RD × ΔI) beyond its base clamping voltage. This allows accurate worst-case overshoot calculation-for example, a 10 A surge yields ~64.5 V + (2.49 Ω × 3.8 A) ≈ 73.9 V-enabling proper margining of downstream IC absolute maximum ratings.
SMAJ40A-TR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Package/Case:
- DO-214AC, SMA
- Series:
- SMAJ, TRANSIL™
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Type:
- Zener
- Unidirectional Channels:
- 1
- Bidirectional Channels:
- -
- Voltage - Reverse Standoff (Typ):
- 40V
- Voltage - Breakdown (Min):
- 44.4V
- Voltage - Clamping (Max) @ Ipp:
- 84V
- Current - Peak Pulse (10/1000µs):
- 27A (8/20µs)
- Power - Peak Pulse:
- 400W
- 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-214AC (SMA)
SMAJ40A-TR FAQ
1.How can I place an order for SMAJ40A-TR through Aetrix?
Please submit a Request for Quotation (RFQ) for SMAJ40A-TR 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 SMAJ40A-TR reliable?
The price and inventory of SMAJ40A-TR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMAJ40A-TR is usually 5 days.
3.What payment methods are accepted for SMAJ40A-TR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMAJ40A-TR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMAJ40A-TR?
SMAJ40A-TR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMAJ40A-TR 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 SMAJ40A-TR?
For technical support, including SMAJ40A-TR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMAJ40A-TR requirements.
6.How does Aetrix verify that SMAJ40A-TR is sourced from the original manufacturer or authorized distributors?
All SMAJ40A-TR 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 SMAJ40A-TR meets industry standards.
7.What is the process for return or replacement of SMAJ40A-TR?
All SMAJ40A-TR units undergo pre-shipment inspection (PSI). If there is an issue with SMAJ40A-TR, 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 SMAJ40A-TR part is unused and in its original packaging.
Return procedure for SMAJ40A-TR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SMAJ40A-TR Tags
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