STMicroelectronics CLT3-4BT6-TR

Overview

CLT3-4BT6-TR from STMicroelectronics is a quad-channel digital input termination IC for 24 V DC industrial automation systems. It integrates over-voltage protection, temperature-compensated 3 mA current limiting per channel, and opto-coupler driver circuitry in a single TSSOP20 package. Designed for PLC digital input modules, it supports IEC 61131-2 Type 1/3 inputs and EN60947-5-2 proximity sensor interfaces with ±6 kV contact ESD immunity.

For engineers reviewing the CLT3-4BT6-TR datasheet, CLT3-4BT6-TR pinout, CLT3-4BT6-TR application, or CLT3-4BT6-TR equivalent, this device delivers robust front-end signal conditioning for noisy factory-floor environments - especially where reverse-polarity resilience, burst/surge immunity (IEC 61000-4-4/4-5), and thermal-efficient termination are critical selection criteria.

Technical Context

The CLT3-4BT6-TR implements four independent termination channels, each combining an input clamping diode, series current limiter (3 mA typ., temp-compensated), and opto-coupler driver with <1.5 mA activation threshold. Input voltage range spans –30 V to +30 V with 1.8 kΩ series resistor, enabling reverse-polarity fault tolerance up to –30 V per channel.

Each channel features low-threshold activation (V_TH = 3.4–5 V at I_IN = 2.1 mA), output drive capability of 1.5–2 mA into opto-LEDs, and off-state leakage <40 µA - ensuring reliable isolation state retention even with high-impedance sensors. The common COM pad (pins 1,3,6,8,10,11,13,15,16,18,20) is thermally enhanced to reduce junction-to-ambient resistance (R_th(j-a) = 90 °C/W).

Key Specifications

Pinout & Package

CLT3-4BT6-TR is housed in a 20-pin TSSOP (Thin Shrink Small Outline Package) with exposed thermal pad. Pin 1 is marked by indentation; pins 1, 3, 6, 8, 10, 11, 13, 15, 16, 18, and 20 are all COM terminals and must be externally shorted to form a single low-impedance, thermally optimized ground plane.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ISO1211 and IL610, CLT3-4BT6-TR uniquely combines quad-channel integration, full IEC-compliant transient protection, and thermally optimized TSSOP20 packaging - eliminating external protection components while delivering superior surge/burst immunity and thermal efficiency in space-constrained PLC modules.

Availability

CLT3-4BT6-TR is available at Aetrix Electronics and suitable for industrial automation, programmable logic controller (PLC) input modules, and fieldbus node designs requiring stable component supply, long-term lifecycle support, and certified EMC robustness.

Supply support for CLT3-4BT6-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 headquartered in Geneva, Switzerland, specializing in automotive, industrial, and power management solutions with strong emphasis on reliability and industrial-grade qualification.

The CLT3-4B belongs to ST's industrial interface portfolio, designed specifically to simplify and harden digital input stages in programmable controllers and I/O modules - targeting compliance with IEC 61131-2, EN60947-5-2, and IEC 61000-4-x standards.

FAQ

What is the maximum allowable reverse input voltage for CLT3-4BT6-TR?

The device withstands –30 V on any IN pin when used with RI = 1.8 kΩ, per IEC 61000-4-2 reverse polarity test conditions. Internal clamping diodes route reverse current to the COM pad, limiting dissipation to <15 mW per channel. This enables safe operation during wiring mistakes or inductive kickback events without latch-up or damage.

Can CLT3-4BT6-TR drive standard PC817-type opto-couplers?

Yes - its 1.5–2 mA ON-state output current and <0.5 V OFF-state voltage fully satisfy PC817's 1.2 mA minimum LED forward current and <0.4 V saturation requirement. The device's insensitivity to output voltage up to 2.0 V ensures compatibility with diverse opto-coupler CTR characteristics and aging effects across temperature.

How does the current limiter behave across temperature?

The limiter is temperature-compensated: ILIM varies only ±6% from –25 °C to +85 °C (typical 3 mA at 25 °C, 2.82 mA at 85 °C). This stability eliminates thermal drift in input threshold voltage and ensures consistent power dissipation - critical for unventilated enclosures where ambient can exceed 70 °C.

Is external capacitor required for EMI filtering?

An external 22 nF capacitor across each OUT pin and COM is recommended per Figure 9 of the datasheet to improve immunity against fast transient bursts (IEC 61000-4-4). Without it, the device still meets Level A functionality but may exhibit marginal margin under worst-case 5 kHz burst injection; the capacitor adds <1 µs propagation delay but enhances noise rejection.