Product Overview
The SM712.TCT from Semtech is a bidirectional TVS diode array specifically designed for RS-485 and RS-422 interface protection. With a working voltage of ±12V to match RS-485 common-mode ranges, it provides IEC 61000-4-2 ESD protection up to ±30kV contact discharge. The low capacitance of 75pF per channel and low clamping voltage of 16V at 5A ensure signal integrity while protecting transceivers from transient threats.
Key Specifications
| Channels | 2 (bidirectional) |
| Working Voltage (VRWM) | ±12V |
| Breakdown Voltage (VBR) | 14V min |
| Clamping Voltage (VC) | 16V max @ IPP = 5A |
| Capacitance | 75pF per channel |
| ESD Protection | IEC 61000-4-2: ±30kV contact |
| Leakage Current | 1µA max @ VRWM |
| Package | SOT-23 (3.0 x 1.3mm) |
| Operating Temperature | -55°C to +125°C |
Features
- Bidirectional protection for RS-485/RS-422 data lines
- IEC 61000-4-2 Level 4 ESD protection (±30kV)
- Low clamping voltage: 16V at 5A protects transceiver inputs
- 75pF per-channel capacitance suitable for RS-485 data rates
- Low leakage current: 1µA max
- Compact SOT-23 package for board-edge placement
- Also protects against EFT and surge per IEC 61000-4-4/5
- RS-485 and RS-422 transceiver protection
- Industrial communication bus protection
- Profibus, Modbus, and DMX512 interfaces
- Building automation and HVAC controllers
- Motor drive communication ports
- Automotive LIN bus protection
- Industrial RS-485 Bus Protection: Place the SM712 at the connector where the RS-485 bus enters the PCB. Connect pin 1 to line A and pin 3 to line B, with pin 2 connected to the bus ground or shield. The ±12V working voltage accommodates the full RS-485 common-mode range, while the ±30kV ESD rating handles cable discharge events common in long industrial cable runs.
- Modbus/Profibus Port Protection: Protect the RS-485 transceiver on Modbus RTU or Profibus DP slave nodes. The low 75pF capacitance does not degrade signal quality at Profibus data rates (up to 12Mbps). Position the SM712 within 10mm of the connector for maximum ESD shunting effectiveness.
- Building Automation Controller: Protect HVAC and BACnet controller communication ports. Cable runs in buildings are susceptible to nearby lightning strikes and switching transients. The SM712’s surge capability (5A) handles these events, while the SOT-23 package fits on the crowded connector area of multi-port controllers.
- Automotive Electronics: All automotive-grade components pass AEC-Q series certification, featuring excellent stability and durability to adapt to complex vehicle operating environments.
- Medical Devices: High-reliability components meet medical industry safety and compliance regulations, ensuring stable operation for medical equipment.
- Industrial Control & Consumer Electronics: Products conform to universal international electronic industry standards, suitable for long-term continuous operation of various equipment.
- Accepted Payment Methods
- T/T (Bank Wire Transfer): The primary settlement method for bulk orders and a widely used international payment channel.
- PayPal: Ideal for small orders, sample orders and quick payments.
Settlement Currency
US Dollar (USD) is the default settlement currency. RMB is available for domestic customers.
Bank Charges
All transfer fees, intermediary bank charges and other remittance-related expenses shall be borne by the buyer.
- Payment Requirements
- Sample and small orders: Shipment will be arranged upon full payment.
- In-stock bulk orders: Goods will be delivered within 2 to 3 working days after full payment.
- Logistics Partners
- International Express: DHL, FedEx, UPS, TNT
- Economy Logistics: Air freight and sea freight for large-volume cargo
- Domestic Delivery: SF Express, Yunda Express
- Order Processing Time
- In-stock items: Orders confirmed and fully paid before 14:00 (GMT+8) will be shipped on the same day. All other orders will be dispatched within 1 to 2 working days.
- Out-of-stock or sourced items: The delivery lead time will be confirmed separately according to brand and inventory status.
- Estimated Transit Time
- International Express: 3 – 7 working days globally
- Air Freight: 7 – 12 working days
- Sea Freight: 25 – 40 working days for heavy and large bulk cargo
- Shipping Fee Rules
- Shipping cost is calculated based on package weight, volume, destination and delivery method.
- Both freight prepaid and freight collect are available. Please provide your courier account number in advance if you choose freight collect.
- Free international express delivery is offered for large orders. Terms for long-term partners can be negotiated separately.
- Shipment Tracking
Within 24 hours after dispatch, we will send the tracking number, commercial invoice, packing list and other documents to your email or communication account. You may check the shipment status online in real time.
MOQ & Sample Service
We support flexible minimum order quantities for samples, small-batch and large-batch orders. All sample orders shall comply with the above shipping and payment policies.
Packaging Standard
All electronic components are packed with professional anti-static and shockproof materials. Original factory packaging is available for branded chips and integrated circuits.
Import Duties & Taxes
All import duties, customs clearance fees and local taxes incurred for international shipments shall be borne by the buyer. We will provide complete customs documents to assist you with clearance procedures.
- Handling of Lost or Damaged Goods
- In case of loss or severe damage during transit, please contact us within 48 hours after receiving the tracking information. We will assist you in filing a claim with the logistics provider.
- We shall not be liable for any losses caused by incorrect delivery address, wrong contact information or the buyer’s refusal to complete customs clearance.
- Address: Room 2919, Guoli Building, Huaqiang North, Futian District, Shenzhen, Guangdong Province, China
- Business Hours: 09:00 – 18:00, Monday to Friday. Closed on weekends and official public holidays.
- Notice: Please make an appointment via email or communication tools one day in advance, and present your order information upon pickup.
- All components are packed separately to avoid damage caused by friction and collision;
- Shockproof buffer materials are added for fragile products to ensure transportation safety;
- Each package is clearly marked with part number, quantity, batch number and specifications for easy inventory counting and management.
- Anti-static Packaging: Static-sensitive components such as chips, circuit boards and sensors are packaged with anti-static bags, shielding boxes and conductive foam in strict accordance with international anti-static standards to prevent static damage.
- Vacuum Moisture-proof Packaging: Moisture-sensitive components are vacuum-sealed with desiccants to isolate humid air, suitable for ocean transportation and long-term storage.
- Original Factory Packaging: Integrated circuits of brands such as NXP are delivered with original reels, trays or tubes by default, retaining complete original packaging and adapting to automated SMT production lines.
- Discrete Device Packaging: Discrete devices such as SMD resistors, power resistors and LEDs are quantitatively and classifiedly packaged with accurate quantity and clear marking.
- Connector / Aviation Connector Packaging: Hard outer packaging is adopted to prevent pin bending and structural deformation.
Applications
The SM712.TCT is a bidirectional transient voltage suppression (TVS) diode array from Semtech, specifically designed for RS-485 and RS-422 interface protection. The ±12V working voltage precisely matches the RS-485 common-mode voltage range of -7V to +12V, allowing the device to protect both the A and B bus lines without interfering with normal signal levels. It provides IEC 61000-4-2 Level 4 ESD protection up to ±30kV contact discharge, as well as protection against electrical fast transients (EFT) and surge events. The low clamping voltage of 16V at 5A ensures that the protected transceiver’s absolute maximum ratings are not exceeded. The compact SOT-23 package allows placement directly at the connector for maximum effectiveness.
The SM712 contains two bidirectional TVS diode structures, each connected between a protected line (A or B) and ground. Under normal operation, the RS-485 signal on each line swings between the common-mode limits (-7V to +12V). The TVS diodes remain in their high-impedance state with only 1µA leakage, having no effect on the signal. When a transient event (ESD, EFT, or surge) pushes the line voltage beyond the ±12V working voltage, the TVS diode avalanches, shunting the transient current to ground. The bidirectional structure provides equal protection for both positive and negative transients. The low clamping voltage (16V at 5A) limits the voltage seen by the transceiver to a safe level. The 75pF capacitance is low enough to not degrade RS-485 signal quality at standard data rates up to 10Mbps.
| Pin | Name | Description |
|---|---|---|
| 1 | Line 1 (A) | Protected RS-485 line A (non-inverting) |
| 2 | GND | Ground connection |
| 3 | Line 2 (B) | Protected RS-485 line B (inverting) |
| Model | VRWM | ESD Rating | Capacitance | Key Difference |
|---|---|---|---|---|
| SM712-02HTG | ±12V | ±30kV | 75pF | Same in SOT-23-6L package |
| TISP4240M3BJR-S | ±12V | ±8kV | 60pF | Bourns alternative, lower cap |
| PRTR5V0U2X | 5V | ±8kV | 0.9pF | Nexperia, USB, not RS-485 |
| NUP4201MR6 | 5V | ±15kV | 4pF | onsemi, CAN bus protection |
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