Protected digital input termination with serialized state transfer

The SCLT3-8BT8 provides an 8-line protected digital input termination with serialized state transfer. This device enhances the I/O module density by cutting the dissipation (78 mW per input) and reducing the count of opto-transistors. An adjustable digital filter and an LED driver are embedded in each type 3 input section. Its 2 MHz SPI peripheral output serializes the input state transfer to the I/O module controller.

Key Features

  • 8-input circuit in common ground low side topology
  • Wide range input DC voltage VI : -30 V to 35 V
    • On state threshold: < 11 V with RI = 2.2 kW
    • Off state threshold: IIN > 1.5 mA or VI > 5 V
    • Protected against -30 V reverse polarity
  • 2.35 mA active current limiter with 10% tolerance
    • Drastic dissipation reduction: 78 mW max. per input
  • Input digital filter with adjustable delay: 20 μs to 3 ms
  • Energy-less LED visual status driver
  • Input logic state transfer through a 2 MHz SPI
    • Programmable 8 / 16-bit register length
    • Multi SCLT connection in daisy chain
    • Chip temperature OTA and under voltage UVA alarms
    • Multi parity bits and power loss detection with stop bits
    • Drastic reduction of isolated coupler count and I/O of the field bus ASIC
  • Power supply and input protection, RI = 2.2 kW:
    • IEC 61000-4-4 transient burst: ±4 kV minimum
    • IEC 61000-4-5 voltage surge: ±1 kV minimum
    • IEC 61000-4-2 ESD: ±8 kV in contact: ± 15 kV in air minimum
  • Wide range power supply voltage VC:
    • +9 V to +35 V with 10 mA output current
    • Protected against -30 V reverse polarity

Circuit Diagram

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Technical Documentation

Product Specifications
Description Version Size
DS5978 DS5978: Protected digital input termination with serialized state transfer 6.0 702 KB
Application Notes
Description Version Size
AN2846 AN2846: SCLT3-8 - guidelines for use in industrial automation applications 1.2 1 MB
AN3031 AN3031: SCLT3-8 input termination demonstration board STEVAL-IFP007V1 1.2 1 MB
Technical Notes & Articles
Description Version Size
TN1173 TN1173: Packing information for IPAD™, protection, rectifiers, thyristors and AC Switches 4.0 330 KB

Publications and Collaterals

Description Version Size
Current-limiting terminations for automation digital inputs 2.1 400 KB
Selection Guides
Description Version Size
Protection devices and integrated EMI filtering selection guide 2.0 743 KB
Description Version Size
Products and Solutions for Factory Automation and Control 1.0 3 MB

Tools and Software

Evaluation Tools
Solution Evaluation Tools

Sample & Buy

Part Number Package Packing Type Marketing Status Unit Price (US$) * Quantity ECCN (EU) ECCN (US) Country of Origin More info Order from ST Order from Distributors
SCLT3-8BT8-TR HTSSOP38 Tape And Reel Active 2.883 10 NEC EAR99 MALAYSIA MORE INFO

(*) Suggested Resale Price per unit (USD) for BUDGETARY USE ONLY. For quotes, prices in local currency, please contact your local ST Sales Office  or our Distributors

Quality & Reliability

Part Number Marketing Status Package Grade RoHS Compliance Grade Material Declaration**
SCLT3-8BT8-TR ActiveHTSSOP38IndustrialEcopack2
SCLT3-8BT8 ActiveHTSSOP38IndustrialEcopack2

(**) The Material Declaration forms available on may be generic documents based on the most commonly used package within a package family. For this reason, they may not be 100% accurate for a specific device. Please contact our sales support for information on specific devices.