TLP781 surface-mount optocoupler SOP-4

TLP781 Surface-Mount Optocoupler SOP-4 is a standard, highly reliable photocoupler that provides critical electrical isolation between two circuits, protecting sensitive low-voltage control systems from high-voltage power lines and noisy environments. This component effectively couples an infrared emitting diode to a silicon NPN phototransistor. The compact SOP-4 (Small Outline Package) design saves significant space on the printed circuit board, making it indispensable for modern, densely packed electronic assemblies. Therefore, the TLP781 is the ideal choice for developers who require excellent isolation voltage, low input current, and fast response times in a surface-mount form factor. Furthermore, its small size and superior performance make it a foundation component in power supply and signaling applications globally.

Key Features:

• High Isolation Voltage: Provides guaranteed minimum isolation voltage of 5000 V_RMS, ensuring superior safety and separation between input and output stages.
• Surface-Mount Package: Utilizes the SOP-4 (Small Outline Package) format, offering a high-density mounting solution that saves PCB real estate compared to standard DIP packages.
• Low Current Transfer Ratio (CTR) Range: Offers a wide range of CTR bins, typically from 50% to 600%, giving designers flexibility in input drive current requirements.
• Fast Switching Speed: Achieves a typical rise time (t_r) and fall time (t_f) in the range of 2 μs to 5 μs, making it suitable for digital signal transfer.
• UL/cUL/VDE Certified: Meets major international safety standards, consequently, simplifying compliance procedures for final products.

Technical Specifications:

• Isolation Voltage (V_ISO): 5000 V_RMS minimum (1 minute)
• Collector-Emitter Voltage (V_CEO): 80 V maximum
• Forward Current (I_F): 50 mA maximum (Input LED)
• Collector Current (I_C): 50 mA maximum (Output Transistor)
• Current Transfer Ratio (CTR): 50% to 600% (I_F = 5 mA, V_CE = 5 V)
• Operating Temperature Range: −55°C to +110°C

Mechanical Specifications:

• Package Type: SOP-4 (Small Outline Package)
• Mounting: Surface Mount Technology (SMT)
• Lead Material: Solderable Alloy
• Moisture Sensitivity Level (MSL): MSL 1 (Unlimited floor life at ≤ 30°C / 85% RH)

Dimensions:

• Body Length (L): ≈ 4.4 mm
• Body Width (W): ≈ 3.6 mm
• Body Height (H): ≈ 2.1 mm (Maximum)
• Pin Pitch (e): 1.27 mm (Standard for SOP packages)
• Weight: ≈ 0.05 g (Extremely low profile and weight)

Pinout and Wiring:

• Pin 1 (Anode): Connect to the control signal source’s positive terminal via a current-limiting resistor (R_limit).
• Pin 2 (Cathode): Connect to the control circuit’s ground (GND).
• Pin 3 (Emitter): Connect to the output circuit’s ground/return path.
• Pin 4 (Collector): Connect to the pull-up resistor (R_L) and the positive supply (V_CC2) of the output circuit. The output signal is typically taken from this pin.

Datasheet Reference:

• Download Toshiba TLP781 Datasheet

Commonly Used in:

• Switching Power Supplies (SMPS): Essential for feedback loops and control signals requiring high-voltage isolation.
• AC/DC Converters: Used for signal coupling and voltage sensing across the isolation barrier.
• Industrial Control Equipment: Protecting sensitive logic circuits from noise and transients generated by relays, motors, and contactors.

Applications:

• Digital Signal Isolation: Transfers digital logic signals between grounds that might have large potential differences.
• Noise Reduction: Effectively eliminates common-mode noise interference in signal lines by breaking the direct electrical connection.
• High-Voltage Safety Interlocks: Provides safety critical isolation in medical equipment and test instrumentation.

Equivalent Models:

• PC817C (Sharp): A very common and often interchangeable optocoupler, although the TLP781 typically offers a higher V_CEO and isolation voltage.
• EL817 (Everlight): Another industry-standard 4-pin transistor output optocoupler that functions as a direct replacement.
• LTV-817S (Lite-On): A functional equivalent available in a surface-mount package, frequently used in similar designs.

Package Includes:

• 1 x TLP781 Surface-Mount Optocoupler SOP-4