TIL924 Dual-Channel Optocoupler Technical Summary

Overview

The TIL924 is a dual-channel optocoupler device that provides electrical isolation between input and output circuits through optical coupling. Each channel consists of a gallium-arsenide (GaAs) light-emitting diode (LED) optically coupled to a silicon n-p-n Darlington phototransistor. This component is part of a series that includes single-channel (TIL923) and quad-channel (TIL925) variants in different package configurations.

The TIL924 is particularly designed for applications requiring high current transfer ratio (CTR), with standard devices tested for a minimum CTR of 500%. This makes it suitable for interfacing between low-current control circuits and higher-current loads while maintaining complete electrical isolation.

Key Features

• Dual-channel isolation: Two independent optocoupler channels in a single 8-pin package
• High current transfer ratio: Minimum 500% CTR for standard devices
• Darlington phototransistor output: Provides high current gain for improved sensitivity
• GaAs LED input: Offers high radiant intensity and reliability
• Electrical isolation: Typical isolation voltage of 2500V_rms between input and output
• Wide operating temperature range: Suitable for industrial environments
• Compact package: 8-pin DIP configuration for space-efficient designs

Applications

The TIL924 optocoupler is designed for a wide range of applications requiring signal isolation and interface between different voltage domains:

• Industrial control systems: PLC I/O isolation, motor control interfaces
• Power supply feedback circuits: Isolated voltage sensing in SMPS designs
• Medical equipment: Patient-isolated monitoring circuits
• Telecommunications: Signal isolation in communication interfaces
• Microprocessor system interfaces: Level shifting and noise isolation
• Automotive electronics: Battery monitoring and high-voltage isolation
• Test and measurement equipment: Isolated signal acquisition

Electrical Characteristics

Absolute Maximum Ratings

• LED forward current (I_F): 60 mA (continuous)
• LED reverse voltage (V_R): 3 V
• Collector-emitter voltage (V_CEO): 30 V
• Emitter-collector voltage (V_ECO): 7 V
• Collector current (I_C): 150 mA
• Total power dissipation: 250 mW per channel
• Isolation voltage: 2500 V_rms (1 minute)
• Operating temperature range: -55°C to +100°C
• Storage temperature range: -55°C to +125°C

Recommended Operating Conditions

• LED forward current (I_F): 10 mA to 20 mA (typical)
• Collector-emitter voltage (V_CE): Up to 15 V
• Ambient temperature (T_A): -40°C to +85°C

Optical Characteristics

• Current transfer ratio (CTR): 500% minimum (standard devices)
• LED forward voltage (V_F): 1.2 V typical at I_F = 10 mA
• Dark current (I_CEO): 100 nA maximum at V_CE = 10 V
• Response time (t_r): 15 μs typical (10% to 90% of I_C)
• Fall time (t_f): 100 μs typical (90% to 10% of I_C)

Package Information

8-Pin Dual Inline Package (DIP)

The TIL924 is available in a standard 8-pin dual inline package with the following mechanical characteristics:

• Package type: Plastic DIP-8
• Mounting style: Through-hole
• Lead material: Solder-plated copper alloy
• Package dimensions: 9.8 mm × 6.35 mm × 3.3 mm (typical)
• Lead pitch: 2.54 mm (0.1 inch)
• Creepage distance: 7.62 mm minimum between input and output sides
• Weight: Approximately 1.2 grams

Pin Configuration

• Pin 1: Anode, Channel 1 LED
• Pin 2: Cathode, Channel 1 LED
• Pin 3: Anode, Channel 2 LED
• Pin 4: Cathode, Channel 2 LED
• Pin 5: Emitter, Channel 2 Phototransistor
• Pin 6: Collector, Channel 2 Phototransistor
• Pin 7: Emitter, Channel 1 Phototransistor
• Pin 8: Collector, Channel 1 Phototransistor

Reliability and Safety

The TIL924 optocoupler is designed to meet stringent reliability and safety standards:

• Isolation voltage: Tested to 2500V_rms for 1 minute between input and output
• UL recognition: Typically recognized under UL1577 for optical isolators
• VDE certification: Compliant with DIN EN 60747-5-2 (VDE 0884-5)
• CTI: Comparative Tracking Index ≥ 175 (material group IIIa)
• Flammability rating: UL94 V-0 for package material

Design Considerations

LED Drive Circuit

For optimal performance, the input LED should be driven with a current-limiting resistor:

• Calculate resistor value: R = (V_CC - V_F) / I_F
• Typical forward current of 10-20 mA provides good balance between CTR and power consumption
• Consider derating for high temperature operation

Output Circuit Design

The Darlington phototransistor output requires careful consideration: