Dual current limited overvoltage protected digital termination

The PCLT-2A is a dual input current limiter device designed for 24 V DC automation applications.

This product is compatible with the type 2 (7.5 mA) or type 3 (3 mA) characteristic of the IEC 61131-2 standard. An internal resistance RREFallows the limiting current value to be adjusted from 3 to 7.5 mA.

Each input voltage clamping block protects the module input against electromagnetic interference such as those described in the IEC 61131-2 standard, IEC 61000-4-2 (ESD), 4-4 (transient burst), 4-5 (voltage surge) and 4-6 (conducted radio frequency interference) standards. The supply input is also designed with such a protection structure.

The low tolerance of the current limitation allows a drastic reduction in the dissipation of the input compared to a resistive input. The PCLT2 is packaged in TSSOP14 - a very low RTHexposed pad package that allows the PCB cooling pad to be reduced.

The output block of each termination channel transfers the input logic state to a logic output and a light emitting diode (LED).

Key Features

  • 2 channel topology: low side input with common ground
  • Wide range input DC voltage:
    • VI = - 0.3 to 30 V with RI = 0 Ω
    • VI = - 30 to 35 V with RI = 750 Ω
  • Current limiter:
    • 3 to 7.5 mA programmable reference
    • ILIM = 6.1 mA to 8.8 mA with RREF = 10 kΩ
    • ILIM = 2.8 mA to 4.3 mA with RREF = 22 kΩ
    • Narrow limiter spread: < 17%
    • Temperature compensated operation
  • Output drive:
    • No output activation below 2 mA input
    • 1.5 mA minimum output activating current in opto-coupler mode
    • Programmable CMOS output mode option (VMOD > 2.9 V)
  • LED drive for sensor status: 4.4 mA typical with RREF = 10 kΩ
  • Input protection (RI = 750 Ω CIN = 22 nF)
  • IEC 61000-4-2 ESD, Level 4
    • In contact, ± 8 kV; in air, ± 15 kV
    • Criteria B: temporary disruption
  • IEC 61000-4-5 voltage surge, Level 3
    • ± 500 V with 42 Ω series resistor in differential mode
    • Criteria B: temporary disruption
  • IEC 61000-4-4 transient burst immunity
    • ± 4 kV peak voltage; 5 kHz repetitive rate
    • Criteria A: fully functional
  • IEC 61000-4-6 conducted RFI
    • 10 VRMS
    • Criteria A: fully functional
  • Input protection against -30 V reverse polarity
  • Ambient temperature: -25 to 85 °C
  • Benefits
    • Enable input to meet type1, 2 and 3 characteristics of IEC 61131-2 standard
    • Compatible operation with 2 and 3 wires proximity sensor according EN60947-5-2 standard
    • Flexible configuration driving either opto- coupler, or CMOS bus controller input, or 12 V AS-Interface network
    • Reduced overall dissipation
    • Enhanced functional reliability
    • Compact with high integration
    • Surface mount package for highly automated assembly
    • Insensitive to the on-state sensor impedance

Circuit Diagram

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Technical Documentation

Product Specifications
Description Version Size
DS4504 DS4504: Dual current limited overvoltage protected digital termination 2.0 601 KB
Application Notes
Description Version Size
AN2482 AN2482: PCLT (Programmable current limited termination) 1.2 859 KB
Technical Notes & Articles
Description Version Size
TN1173 TN1173: Packing information for IPAD™, protection, rectifiers, thyristors and AC Switches 5.0 1 MB

Publications and Collaterals

Description Version Size
Current-limiting terminations for automation digital inputs 2.1 400 KB
ST Protection Finder - The new app for Android and iOS 1.0 1 MB
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Protection devices and integrated EMI filtering selection guide 2.0 743 KB
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Products and solutions for Smart industry 2.0 5 MB

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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

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Quality & Reliability

Part Number Marketing Status Package Grade RoHS Compliance Grade Material Declaration**
PCLT-2AT4-TR ActiveHTSSOP14IndustrialEcopack2 0 0
PCLT-2AT4 ActiveHTSSOP14IndustrialEcopack2 0 0

(**) The Material Declaration forms available on st.com 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.