TIL191 Optocoupler Technical Summary

Overview

The TIL191 is a single-channel optocoupler designed to provide electrical isolation between input and output circuits. It consists of a gallium-arsenide (GaAs) infrared light-emitting diode (LED) optically coupled to a silicon NPN phototransistor. This configuration ensures reliable signal transmission while maintaining high voltage isolation. The TIL191 is part of a family of optocouplers that includes the dual-channel TIL192 (8-pin package) and quad-channel TIL193 (16-pin package).

Key to its performance is the current-transfer ratio (CTR), which defines the efficiency of signal transfer between the LED and phototransistor. The standard TIL191 is tested for a minimum CTR of 20%, while higher-performance variants (TIL191A and TIL191B) offer guaranteed minimum CTRs of 50% and 100% respectively.

Features

• High Isolation Voltage: Provides safe electrical isolation between input and output circuits
• Compact 4-Pin Package: Space-efficient DIP (Dual In-line Package) design
• GaAs LED with Silicon Phototransistor: Optimized for efficient infrared light coupling
• Current-Transfer Ratio Options: Standard (20% min), A-grade (50% min), and B-grade (100% min) versions available
• Fast Response Time: Suitable for moderate speed digital signal isolation
• Wide Operating Temperature Range: Typically -55°C to +100°C
• Reliable Performance: Robust construction for industrial applications

Applications

The TIL191 optocoupler finds use in numerous applications requiring electrical isolation and signal transmission:

• Industrial Control Systems: Isolating logic circuits from power stages
• Power Supply Feedback Circuits: Providing isolated voltage feedback
• Medical Equipment: Meeting safety isolation requirements
• Telecommunications: Signal isolation in communication interfaces
• Microprocessor System Interfaces: Protecting sensitive logic from high voltages
• Automotive Electronics: Noise-resistant signal transmission
• Test and Measurement Equipment: Isolating measurement circuits

Electrical Characteristics

Absolute Maximum Ratings

• LED Forward Current: 60 mA (continuous)
• LED Peak Forward Current: 1 A (1 μs pulse width, 300 Hz max)
• Reverse Voltage (LED): 3 V
• Collector-Emitter Voltage: 30 V
• Emitter-Collector Voltage: 7 V
• Collector Current: 50 mA
• Total Power Dissipation: 150 mW at 25°C
• Isolation Voltage: 2500 V_rms (1 minute)
• Operating Temperature Range: -55°C to +100°C
• Storage Temperature Range: -55°C to +125°C

Typical Electrical Characteristics (T_A = 25°C unless otherwise noted)

• LED Forward Voltage: 1.15 V (typical) at I_F = 10 mA
• LED Reverse Current: 10 μA (max) at V_R = 3 V
• Collector-Emitter Breakdown Voltage: 30 V (min)
• Dark Current: 50 nA (max) at V_CE = 10 V
• Current-Transfer Ratio (CTR):
  • TIL191: 20% minimum
  • TIL191A: 50% minimum
  • TIL191B: 100% minimum
• Rise Time: 3 μs (typical) at I_F = 10 mA, V_CC = 10 V, R_L = 100 Ω
• Fall Time: 2 μs (typical) under same conditions
• Isolation Resistance: 10¹¹ Ω (min) at V_ISO = 500 V
• Input-Output Capacitance: 0.5 pF (typical)

Package Information

4-Pin DIP Package Dimensions

• Package Type: Standard DIP-4 (Dual In-line Package)
• Body Material: Molded plastic, UL 94V-0 rated
• Lead Material: Copper alloy, tin-plated
• Pin Spacing: 2.54 mm (0.1 inch) between pins
• Row Spacing: 7.62 mm (0.3 inch) between rows
• Body Length: 5.08 mm (0.2 inch)
• Body Width: 6.35 mm (0.25 inch)
• Height: 3.81 mm (0.15 inch)
• Lead Length: 3.18 mm (0.125 inch) below seating plane

Pin Configuration

• Pin 1: Anode of LED (Input side)
• Pin 2: Cathode of LED (Input side)
• Pin 3: Emitter of Phototransistor (Output side)
• Pin 4: Collector of Phototransistor (Output side)

Performance Considerations

Current-Transfer Ratio (CTR) Characteristics

The CTR is a critical parameter defined as the ratio of output collector current to input LED current, expressed as a percentage. The TIL191 family offers three CTR grades:

• Standard Grade (TIL191): 20% minimum CTR ensures basic signal transfer capability
• A Grade (TIL191A): 50% minimum CTR provides improved efficiency
• B Grade (TIL191B): 100% minimum CTR offers highest sensitivity

CTR is temperature-dependent, typically decreasing at higher temperatures. Designers should account for this variation in critical applications.

Temperature Performance

The TIL191 maintains reliable operation across its specified temperature range (-55°C to +100°C). Key temperature-related considerations include:

• LED forward voltage has a negative temperature coefficient (~2 mV/°C)
• Phototransistor gain decreases with increasing temperature
• Dark current increases exponentially with temperature
• Maximum allowable power dissipation decreases at higher ambient temperatures

Reliability and Safety

The TIL191 optocoupler meets industry standards for reliability and safety: