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onsemi SMF85AT1
- Part No.:
- SMF85AT1
- Manufacturer:
- onsemi
- Category:
- TVS Diodes
- Package:
- SOD-123F
- Datasheet:
-
SMF85AT1.pdf
- Description:
- TVS DIODE 85VWM 137VC SOD123FL
- Quantity:
- Payment:
- Shipping:
Inventory:2,974
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Product details
Overview
SMF85AT1 from onsemi is a unidirectional transient voltage suppressor (TVS) diode designed for overvoltage protection in DC power rails and signal lines. It features a working peak reverse voltage (VRWM) of 85 V, maximum clamping voltage (VC) of 137 V at 1.3 A peak pulse current (IPP), 200 W peak pulse power rating (10/1000 µs), <1 ns response time, and IEC61000-4-2 Level 4 ESD immunity (>16 kV HBM). It is used in industrial power supplies and telecom interface circuits requiring robust surge suppression.
For engineers reviewing the SMF85AT1 datasheet, pinout, applications, or equivalent options, key selection criteria include VRWM ≥ system operating voltage, VC margin relative to protected IC absolute maximum ratings, IPP capability under defined surge waveforms (10/1000 µs), thermal derating at elevated ambient temperatures, and SOD−123FL footprint compatibility with high-density PCB layouts.
Technical Context
The SMF85AT1 operates as a Zener-based avalanche clamp, entering conduction when reverse voltage exceeds its breakdown threshold (VBR = 94.4–104 V @ IT = 1 mA). Its low dynamic impedance ensures stable clamping during fast transients such as ESD or lightning-induced surges. The device is optimized for single-polarity (unidirectional) protection where the protected line remains biased near ground or a fixed DC rail.
Thermal performance is governed by RθJA = 325°C/W (with recommended FR-4 pad layout), limiting steady-state dissipation to 385 mW at 25°C ambient. Pulse power handling relies on junction thermal mass and short-duration energy absorption-derated per Figure 4 above 25°C-and requires no external heat sinking due to its surface-mount SOD−123FL construction.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VRWM | 85 V - Maximum continuous reverse voltage before significant leakage; must exceed circuit's peak operating voltage to avoid false triggering. |
| VBR (min/max) | 94.4 V / 104 V @ 1 mA - Breakdown onset range; defines minimum clamping threshold and ensures margin against overvoltage misfire. |
| VC @ IPP | 137 V @ 1.3 A (10/1000 µs) - Maximum clamped voltage seen by downstream components during worst-case surge event. |
| IPP (max) | 1.3 A - Peak pulse current the device safely shunts without degradation; determines survivability under IEC61000-4-4 40 A surge (with appropriate series impedance). |
| Response Time | <1 ns - Enables protection of high-speed interfaces (e.g., RS-485, CAN) against sub-nanosecond ESD transients. |
| ESD Rating | >16 kV HBM, IEC61000-4-2 Level 4 - Validated immunity to human-body-model and contact-discharge ESD events per international standards. |
| Package | SOD−123FL (Case 498) - Low-profile (1.0 mm max height), small-footprint (8.45 mm²) surface-mount package compatible with automated reflow assembly. |
Pinout & Package
SOD−123FL is a two-terminal surface-mount package with cathode indicated by a polarity band. The device has no internal active circuitry-only an integrated Zener junction-so terminal roles are strictly anode/cathode for unidirectional clamping.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (Banded End) | Cathode | Connected to protected line's higher-potential side (e.g., VCC rail); reverse-biased during normal operation; conducts surge current to ground when clamping. |
| 2 (Non-banded End) | Anode | Connected to circuit reference (typically GND); provides return path for surge current; must be routed with low-inductance connection to maintain clamping integrity. |
Key Features
| Feature | Design Value |
|---|---|
| Low Clamping Ratio (VC/VBR) | 1.37–1.45 - Tight ratio ensures minimal overvoltage overshoot during surge, protecting downstream ICs with narrow absolute maximum voltage margins. |
| Ultra-Fast Response | <1 ns turn-on - Critical for suppressing ESD events before logic-level interfaces (e.g., microcontroller GPIOs) experience latch-up or gate oxide damage. |
| High Surge Robustness | 200 W peak power (10/1000 µs) - Withstands repeated industrial-grade surges (IEC61000-4-4) without parameter shift or failure when properly applied. |
| Small Footprint & Low Profile | 8.45 mm² area, 1.0 mm max height - Enables placement directly at connector or IC entry points in space-constrained portable and telecom equipment. |
| ESD & Surge Dual Certification | IEC61000-4-2 Level 4 + IEC61000-4-4 40 A - Single-device compliance eliminates need for cascaded protection stages in cost-sensitive designs. |
Applications
| Industrial Power Supply Input Protection | Telecom Line Interface Protection |
|---|---|
Use Scenario: 24–48 V DC input stage of programmable logic controllers (PLCs) exposed to load dump and inductive switching transients. IC Role / Device Role / Timing Role: Unidirectional TVS placed between VIN and GND to clamp positive-going surges before they reach DC-DC converter input capacitors and control ICs. Use Value: Limits transient voltage to ≤137 V, preventing overstress of 60 V-rated input MOSFETs and ensuring uninterrupted operation during EN 61000-4-4 testing. |
Use Scenario: RS-485 data lines in building automation nodes connected to long outdoor cable runs susceptible to induced lightning surges. IC Role / Device Role / Timing Role: Paired SMF85AT1 devices (one per line) referenced to local ground, providing common-mode surge suppression on differential bus lines. Use Value: Clamps 1 kV/10/1000 µs surges to safe levels (<137 V) while maintaining signal integrity up to 10 Mbps due to low capacitance (~50 pF at 0 V). |
| Automotive Body Control Module (BCM) Inputs | Medical Equipment Sensor Interface Protection |
Use Scenario: 12 V supply inputs to BCM microcontrollers receiving signals from door switches, seat sensors, and lighting controls. IC Role / Device Role / Timing Role: Primary overvoltage clamp on fused 12 V rail, positioned upstream of LDO regulators to absorb ISO 7637-2 Pulse 1/2a transients. Use Value: Survives 100 V/100 ms load-dump pulses (via series impedance limiting IPP) and maintains VRWM margin above nominal 13.5 V battery voltage. |
Use Scenario: Analog front-end of patient monitoring devices where thermistor or pressure sensor lines enter the main PCB from external probes. IC Role / Device Role / Timing Role: Low-leakage (IR ≤ 1 µA @ 85 V) TVS on sensor analog lines to prevent ESD-induced offset drift or ADC saturation without affecting DC accuracy. Use Value: Provides >16 kV HBM ESD protection while adding <0.1% gain error to 24-bit sigma-delta ADC measurements due to sub-µA leakage at operating bias. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient voltage suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMAJ85A | Same VRWM (85 V), but SMA package (larger footprint, higher RθJA = 40°C/W), 400 W peak power rating. | Better thermal handling for higher-duty-cycle surges; less suitable for ultra-compact layouts. | Select SMAJ85A only if board space allows larger package and higher pulse energy (e.g., automotive alternator load dump) is required. |
| 1.5SMC85A | Same VRWM, DO-214AB package, 1500 W peak power, higher VC (139 V), slower response (~5 ns). | Higher surge capacity but greater clamping overshoot and larger board area; not ideal for high-speed signal lines. | Choose 1.5SMC85A for mains-connected AC/DC adapters needing higher IEC61000-4-5 surge rating, not for space- or speed-critical DC rails. |
Compared with SMAJ85A and 1.5SMC85A, the SMF85AT1 offers optimal balance of compact size, fast response, and certified ESD/surge performance for modern embedded systems-making it preferred where PCB real estate and signal integrity are constrained, despite lower absolute pulse power than larger packages.
Availability
SMF85AT1 is available at Aetrix Electronics and suitable for industrial power supplies, telecom interface modules, automotive body electronics, and medical sensor interfaces requiring stable component supply and full traceability through production lifecycles.
Supply support for SMF85AT1 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
onsemi (formerly ON Semiconductor) is a global semiconductor supplier specializing in energy-efficient power management, analog, sensing, and connectivity solutions for automotive, industrial, cloud, and consumer markets.
The SMF5.0AT1 Series-including SMF85AT1-is part of onsemi's transient voltage suppressor portfolio engineered specifically for reliable, low-profile overvoltage protection in high-volume, space-constrained applications across industrial and communications infrastructure.
FAQ
What is the maximum clamping voltage of the SMF85AT1 under standard test conditions?
The SMF85AT1 has a maximum clamping voltage (VC) of 137 V when subjected to its rated peak pulse current (IPP) of 1.3 A using the 10/1000 µs waveform. This value is measured at the device terminals and represents the highest voltage that will appear across the SMF85AT1 during a standardized surge event-critical for verifying margin against downstream component absolute maximum ratings.
Can the SMF85AT1 be used for bidirectional transient protection?
No, the SMF85AT1 is a unidirectional TVS diode and is not suitable for bidirectional protection. It conducts only in reverse bias (cathode positive relative to anode) and blocks forward current like a standard diode. For AC or bipolar signal lines, a bidirectional variant such as SMBJ85CA or a back-to-back SMF85AT1 pair would be required-not the SMF85AT1 alone.
What is the leakage current specification for SMF85AT1 at its working voltage?
The SMF85AT1 specifies a maximum reverse leakage current (IR) of 1 µA at its working peak reverse voltage (VRWM) of 85 V, measured at 25°C. This low leakage ensures minimal power loss and negligible impact on high-impedance sensor or reference circuits where the SMF85AT1 is deployed-such as medical analog front-ends or precision voltage monitors.
Does the SMF85AT1 meet IEC61000-4-2 and IEC61000-4-4 immunity standards?
Yes, the SMF85AT1 is rated for IEC61000-4-2 Level 4 ESD protection (>16 kV contact discharge) and provides 40 A surge immunity per IEC61000-4-4 (5/50 ns rise, 50 ns duration) when used with appropriate series impedance. These certifications are explicitly stated in the official onsemi datasheet for the SMF5.0AT1 Series, confirming the SMF85AT1's suitability for end-equipment compliance testing.
What is the thermal resistance and power derating behavior of SMF85AT1?
The SMF85AT1 has a junction-to-ambient thermal resistance (RθJA) of 325°C/W when mounted on the recommended FR-4 PCB footprint. Its steady-state power dissipation is derated linearly above 25°C ambient, reaching zero at 150°C. At 85°C ambient, the SMF85AT1 is limited to approximately 200 mW continuous power-important for thermal design in enclosed industrial enclosures where the SMF85AT1 may operate near other heat-generating components.
SMF85AT1 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Package/Case:
- SOD-123F
- Series:
- -
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Type:
- Zener
- Unidirectional Channels:
- 1
- Bidirectional Channels:
- -
- Voltage - Reverse Standoff (Typ):
- 85V
- Voltage - Breakdown (Min):
- 94.4V
- Voltage - Clamping (Max) @ Ipp:
- 137V
- Current - Peak Pulse (10/1000µs):
- 1.3A
- Power - Peak Pulse:
- 200W
- 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:
- SOD-123FL
SMF85AT1 FAQ
1.How can I place an order for SMF85AT1 through Aetrix?
Please submit a Request for Quotation (RFQ) for SMF85AT1 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 SMF85AT1 reliable?
The price and inventory of SMF85AT1 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMF85AT1 is usually 5 days.
3.What payment methods are accepted for SMF85AT1?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMF85AT1 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMF85AT1?
SMF85AT1 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMF85AT1 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 SMF85AT1?
For technical support, including SMF85AT1 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMF85AT1 requirements.
6.How does Aetrix verify that SMF85AT1 is sourced from the original manufacturer or authorized distributors?
All SMF85AT1 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 SMF85AT1 meets industry standards.
7.What is the process for return or replacement of SMF85AT1?
All SMF85AT1 units undergo pre-shipment inspection (PSI). If there is an issue with SMF85AT1, 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 SMF85AT1 part is unused and in its original packaging.
Return procedure for SMF85AT1:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SMF85AT1 Tags
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ESD9B5.0ST5G
onsemi
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DESD3V3E1BL-7B
Diodes Incorporated
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ESD5Z3.3T1G
onsemi
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D5V0H1B2LP-7B
Diodes Incorporated
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D5V0P1B2LP-7B
Diodes Incorporated
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DESD5V0U1BA-7
Diodes Incorporated
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ESD5Z5.0T1G
onsemi
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DESD5V0U1BB-7
Diodes Incorporated
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D12V0L1B2LP-7B
Diodes Incorporated
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PESD2V0Y1BSFYL
Nexperia USA Inc.
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DF2S5M4CT,L3F
Toshiba Semiconductor and Storage
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D5V0L1B2WS-7
Diodes Incorporated
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