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STMicroelectronics SMAJ85CA-TR
- Part No.:
- SMAJ85CA-TR
- Manufacturer:
- STMicroelectronics
- Category:
- TVS Diodes
- Package:
- DO-214AC, SMA
- Datasheet:
-
SMAJ85CA-TR.pdf
- Description:
- TVS DIODE 85VWM 178VC SMA
- Quantity:
- Payment:
- Shipping:
Inventory:9,148
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Product details
Overview
SMAJ85CA-TR from STMicroelectronics is a bidirectional transient voltage suppression (TVS) diode designed for ESD and surge protection in DC power rails and signal lines. It features a standoff voltage (VRM) of 85 V, clamping voltage (VCL) of 137 V at 2.9 A (10/1000 µs), peak pulse power of 400 W, and operates up to 150 °C junction temperature. It is used in industrial power supplies, automotive body electronics, and telecom interface protection.
For engineers reviewing the SMAJ85CA-TR datasheet, SMAJ85CA-TR pinout, SMAJ85CA-TR application, or SMAJ85CA-TR equivalent, key selection criteria include bidirectional clamping behavior, low leakage (<0.2 µA at 25 °C), JEDEC DO-214AC (SMA) package compatibility, IEC 61000-4-2 level 4 (±30 kV contact/air) and IEC 61000-4-4 level 4 (4 kV) compliance, and thermal stability across -55 °C to +150 °C.
Technical Context
This TVS diode uses planar silicon technology to achieve low leakage current and high junction temperature capability. Its bidirectional configuration enables symmetrical clamping for AC-coupled or floating signal paths without polarity dependency.
The device complies with IEC 61000-4-2 (ESD) and IEC 61000-4-4 (EFT) immunity standards, delivering 30 kV air/contact discharge protection and 4 kV surge immunity. Its dynamic resistance (RD = 5.70 Ω at 25 °C) ensures predictable voltage limiting under fast transients.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Standoff Voltage (VRM) | 85 V - Maximum continuous reverse working voltage before clamping begins |
| Breakdown Voltage (VBR) | 94–99 V at 1 mA - Confirmed avalanche onset range ensuring reliable triggering |
| Clamping Voltage (VCL) | 137 V at 2.9 A (10/1000 µs) - Peak voltage seen by protected circuit during surge |
| Peak Pulse Power (PPP) | 400 W (10/1000 µs) - Sustained surge energy handling per IEC standard waveform |
| Leakage Current (IRM) | 0.2 µA max at 25 °C - Minimal DC loading on high-impedance circuits |
| Junction Temperature (Tj) | -55 °C to +150 °C - Enables operation in under-hood automotive or industrial enclosures |
| ESD Rating | ±30 kV (IEC 61000-4-2, contact/air) - Full level 4 immunity without external shielding |
Pinout & Package
Package: DO-214AC (SMA), JEDEC registered, IPC-7531 compliant footprint, matte tin-plated leads, MSL Level 1.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Cathode (K) | Surge return path (bidirectional) | Shared terminal for both polarities; connects to ground or common reference plane |
| Anode (A) | Surge return path (bidirectional) | Shared terminal opposite cathode; forms symmetrical clamping pair with K |
Key Features
| Feature | Design Value |
|---|---|
| Bidirectional clamping | Enables protection of AC signals or floating buses without polarity constraints |
| Low junction capacitance | ~100 pF at 0 V (typical) - Minimizes signal distortion in data lines up to 100 Mbps |
| High-temperature reliability | Rated for 150 °C Tj - Supports long-term operation in thermally stressed environments |
| JEDEC-compliant solderability | MSL Level 1, 260 °C lead temperature - Compatible with standard reflow profiles without baking |
| UL94 V0 flammability rating | Self-extinguishing epoxy housing - Meets safety requirements for enclosed industrial equipment |
Applications
| Industrial Power Input Protection | Automotive Body Control Module (BCM) |
|---|---|
Use Scenario: 24 V DC input rail in programmable logic controllers exposed to load dump and inductive switching transients. IC Role / Device Role / Timing Role: Primary overvoltage clamp placed between VIN and GND, responding within <1 ns to limit voltage to ≤137 V. Use Value: Prevents damage to downstream DC-DC converters and microcontrollers during ISO 7637-2 pulse 5a (load dump) events. | Use Scenario: LIN bus transceiver power supply line in door module electronics subject to ESD and battery reversal. IC Role / Device Role / Timing Role: Bidirectional TVS placed across VCC-GND to suppress ±30 kV ESD and clamp reverse polarity surges. Use Value: Maintains LIN communication integrity by limiting voltage excursions below transceiver absolute maximum ratings (typically ±40 V). |
| Telecom Ethernet PHY Interface | Smart Meter RS-485 Port |
Use Scenario: 3.3 V bias rail feeding Ethernet magnetics and PHY ICs in outdoor base station equipment. IC Role / Device Role / Timing Role: Secondary protection device after gas discharge tube (GDT), clamping fast-rising EFT bursts on power domain. Use Value: Limits transient-induced latch-up risk in PHY ICs by holding rail voltage within 10 % of nominal during 4 kV IEC 61000-4-4 bursts. | Use Scenario: VCC line of isolated RS-485 transceiver in utility smart meters installed in electrically noisy substations. IC Role / Device Role / Timing Role: Standoff-rated TVS on transceiver VCC, triggered only during >85 V surges to avoid false activation during normal operation. Use Value: Extends field lifetime by preventing cumulative degradation of transceiver internal LDOs from repeated low-energy surges. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar TVS diode applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMBJ85CA-TR | Higher PPP (600 W), larger SMB (DO-214AA) package, same VRM/VCL | Requires more PCB area; better suited for higher-energy surges | Select when system-level testing reveals >400 W surge margin is insufficient |
| P6SMB85CA | Same VRM/VCL/PPP, but legacy SMB package with non-MSL-1 lead finish | Limited reflow compatibility; not recommended for new designs with lead-free assembly | Use only for legacy repair or backward-compatible BOMs where MSL Level 1 is not required |
Compared with SMBJ85CA-TR and P6SMB85CA, SMAJ85CA-TR offers optimal balance of compact DO-214AC footprint, MSL Level 1 manufacturability, and verified 400 W surge handling-making it ideal for space-constrained, high-volume industrial and automotive modules requiring robust ESD immunity without over-engineering.
Availability
SMAJ85CA-TR is available at Aetrix Electronics and suitable for industrial power input protection, automotive body control modules, telecom Ethernet PHY interfaces, and smart meter RS-485 ports requiring stable component supply and full IEC 61000-4-2/4-4 compliance.
Supply support for SMAJ85CA-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, analog, MEMS, and microcontroller technologies for industrial, automotive, and consumer markets.
The SMAJ series belongs to ST's transient protection product line, engineered specifically for high-reliability DC and signal-line surge suppression in harsh electromagnetic environments where low leakage, thermal stability, and standardized packaging are critical.
FAQ
What is the difference between SMAJ85CA-TR and SMAJ85A-TR?
SMAJ85CA-TR is bidirectional, providing symmetrical clamping for AC or floating circuits, while SMAJ85A-TR is unidirectional and must be oriented with cathode toward the protected line. The CA version has identical electrical specs except for polarity behavior and slightly higher leakage above 85 °C due to dual-junction structure.
Can SMAJ85CA-TR be used in place of a 75 V standoff TVS?
No-substituting a higher VRM device risks inadequate clamping during lower-voltage transients. SMAJ85CA-TR is rated for 85 V standoff; using it where 75 V is specified may allow damaging overvoltage before clamping initiates. Always match VRM to the protected circuit's maximum steady-state voltage.
Does this device require a heatsink for 400 W pulse handling?
No-its 400 W rating applies to single 10/1000 µs pulses with no sustained power dissipation. Thermal design focuses on PCB copper area: ≥1.64 cm² per pad (per Figure 12) ensures adequate transient heat spreading without heatsinks or forced airflow.
Is SMAJ85CA-TR compliant with AEC-Q200 for automotive use?
No-it is not AEC-Q200 qualified. While it meets IEC 61000-4-2/4-4 and operates up to 150 °C, ST does not certify SMAJ devices for automotive qualification. For AEC-Q200 applications, consider ST's Automotive-grade SMxJ series (e.g., SMAJ85CAQ-TR) with full stress test documentation.
SMAJ85CA-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:
- -
- Bidirectional Channels:
- 1
- Voltage - Reverse Standoff (Typ):
- 85V
- Voltage - Breakdown (Min):
- 94V
- Voltage - Clamping (Max) @ Ipp:
- 178V
- Current - Peak Pulse (10/1000µs):
- 13A (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)
SMAJ85CA-TR FAQ
1.How can I place an order for SMAJ85CA-TR through Aetrix?
Please submit a Request for Quotation (RFQ) for SMAJ85CA-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 SMAJ85CA-TR reliable?
The price and inventory of SMAJ85CA-TR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMAJ85CA-TR is usually 5 days.
3.What payment methods are accepted for SMAJ85CA-TR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMAJ85CA-TR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMAJ85CA-TR?
SMAJ85CA-TR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMAJ85CA-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 SMAJ85CA-TR?
For technical support, including SMAJ85CA-TR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMAJ85CA-TR requirements.
6.How does Aetrix verify that SMAJ85CA-TR is sourced from the original manufacturer or authorized distributors?
All SMAJ85CA-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 SMAJ85CA-TR meets industry standards.
7.What is the process for return or replacement of SMAJ85CA-TR?
All SMAJ85CA-TR units undergo pre-shipment inspection (PSI). If there is an issue with SMAJ85CA-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 SMAJ85CA-TR part is unused and in its original packaging.
Return procedure for SMAJ85CA-TR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SMAJ85CA-TR Tags
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Diodes Incorporated
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