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Protected digital input termination with serialized state transfer
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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.

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Errata Sheet
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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

Design Resources


Technical Documentation

Product Specifications

Description Version Size
DS5978: Protected digital input termination with serialized state transfer
6.0 702 KB

Application Notes

Description Version Size
AN2846: SCLT3-8 - guidelines for use in industrial automation applications
1.2 1,077 KB
AN3031: SCLT3-8 input termination demonstration board STEVAL-IFP007V1
1.2 1,372 KB

Technical Notes & Articles

Description Version Size
TN1173: Packing information for IPAD™, protection, rectifiers, thyristors and AC Switches
3.1 333 KB

Related Tools and Software

Related Tools and Software

Part Number Description
STEVAL-IFP007V1 16-bit PLC digital input card demonstration board based on the SCLT3

Publications and Collaterals


Description Version Size
Current-limiting terminations for automation digital inputs
1.0 401 KB

Selection Guides

Description Version Size
Protection devices and integrated EMI filtering selection guide
1,537 KB


Description Version Size
Products and Solutions for Factory Automation and Control
Jan 2015 3,105 KB

Sample & Buy

Part Number Marketing StatusPackagePacking TypeOrder From STUnit Price (US$)*
@ 10
Distributor AvailabilityRoHS Compliance GradeDownload
Material Declaration**
SCLT3-8BT8ActiveHTSSOP38Tube-2.883Distributor reported inventory date: 2016-02-13
Distributor NameRegionStockMin. order
Farnell Element14Order NowEUROPE831
SCLT3-8BT8-TRActiveHTSSOP38Tape And Reel-2.883No availability reported, please contact our Sales officeEcopack2-

(*) 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
(**) 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.
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