STMicroelectronics PCLT-2AT4-TR

Overview

PCLT-2AT4-TR from STMicroelectronics is a dual-channel digital input termination IC for 24 V industrial automation systems, implementing IEC 61131-2 Type 2 (7.6 mA typical) or Type 3 (3.6 mA typical) current-limited logic inputs with overvoltage protection, programmable CMOS/opto-coupler output mode via VMOD pin, and integrated LED status indication. It operates from −30 V to +35 V input (with 750 Ω series resistor), delivers <17% current limiter spread, and supports AS-Interface bus termination.

For engineers reviewing the PCLT-2AT4-TR datasheet, PCLT-2AT4-TR pinout, PCLT-2AT4-TR application, or PCLT-2AT4-TR equivalent, key selection considerations include its dual-channel current-limiting accuracy across −25 °C to +85 °C, IEC 61000-4-2/4-4/4-5/4-6 immunity compliance, TSSOP14 exposed-pad thermal performance (R_TH(j-a) = 100 °C/W), and flexible output configuration (opto-coupler drive ≥1.5 mA or CMOS level-shifting).

Technical Context

The PCLT-2AT4-TR integrates two independent current-limiting channels, each with programmable reference (R_REF = 10 kΩ or 22 kΩ), temperature-compensated clamping, and dual-mode output interface selectable by VMOD voltage (≤0.75 V for opto-coupler drive; ≥2.9 V for CMOS buffer). Input protection includes reverse polarity tolerance (−30 V), ESD (±8 kV contact), surge (±500 V differential), and burst (±4 kV) immunity per IEC 61000-4 standards.

Each channel features low-threshold activation (V_LOW = 1.5–3 V), precise ON-state current sharing (60% to LED, 30% to output in opto mode), and propagation delays of 0.1 µs (TPHL) and 16 µs (TPLH) at 24 V supply. The device uses internal biasing to maintain stable current limiting independent of output voltage up to 2.5 V.

Key Specifications

Pinout & Package

Package: TSSOP14 with exposed thermal pad - provides low junction-to-ambient thermal resistance (100 °C/W) for high-density industrial PCB layouts without heatsinks.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-channel digital input termination applications.

Compared with MAX14912 and IL420, the PCLT-2AT4-TR uniquely combines dual-channel programmable current limiting, full IEC 61000-4 immunity, LED status, and hardware-selectable output mode in a single TSSOP14 package-reducing component count by ≥60% versus discrete alternatives while maintaining direct compatibility with existing PLC and AS-Interface hardware.

Availability

PCLT-2AT4-TR is available at Aetrix Electronics and suitable for industrial automation, AS-Interface bus nodes, and programmable logic controller I/O modules requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for PCLT-2AT4-TR 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

STMicroelectronics is a global semiconductor leader specializing in automotive, industrial, and power management ICs, with over 40 years of expertise in high-reliability analog and mixed-signal products for harsh environments.

The PCLT-2AT4-TR belongs to ST's Industrial Digital Input Interface product line, designed specifically to replace discrete resistor-diode-LED networks in PLCs, distributed I/O, and fieldbus nodes-prioritizing IEC standard compliance, thermal efficiency, and layout simplification.

FAQ

What is the maximum allowable input voltage for PCLT-2AT4-TR when using a 750 Ω series resistor?

The absolute maximum input voltage is −30 V to +35 V with RI = 750 Ω, as verified in Table 1 of the official datasheet (Doc ID 11821 Rev 2). This rating covers reverse polarity events and transient surges per IEC 61000-4-5 Level 3 testing, and remains valid across the full −25 °C to +85 °C operating ambient range.

How does the VMOD pin determine output behavior, and what voltage thresholds are guaranteed?

The VMOD pin selects between opto-coupler drive (VMOD ≤ 0.75 V) and CMOS buffer mode (VMOD ≥ 2.9 V), with guaranteed hysteresis to prevent oscillation. In CMOS mode, the output sources 35–65 µA and swings between 20% and 80% of VMOD voltage, enabling direct interfacing with 3.3 V or 5 V bus controllers without level shifters.

Can PCLT-2AT4-TR be used with both 2-wire and 3-wire proximity sensors, and what external components are required?

Yes-it supports both topologies per EN 60947-5-2. For 2-wire sensors, connect INx to sensor output and COMS to sensor return; for 3-wire, use INx and COMS with external 750 Ω resistor. Required external parts are only R_REF (10 kΩ or 22 kΩ), RC (2.2 kΩ), and optional LED anode resistor-no TVS diodes or optocouplers needed due to integrated protection.

What thermal derating applies when operating at 85 °C ambient temperature?

At T_AMB = 85 °C, the maximum power dissipation is limited by R_TH(j-a) = 100 °C/W to ensure T_J ≤ 150 °C. With typical channel dissipation of 120 mW (24 V × 5 mA), junction temperature rises to 85 °C + (120 mW × 100 °C/W) = 97 °C-well within safe margin. No derating is required for standard operation.