EL357N-C Phototransistor Opto-Coupler SOP-4

EL357N-C Phototransistor Opto-Coupler SOP-4 is a compact and highly reliable solution for achieving electrical isolation between two separate circuits, safeguarding sensitive components from voltage spikes and ground loops. This device pairs a gallium arsenide infrared emitting diode with a silicon NPN phototransistor, creating a complete optical barrier within a small SOP-4 package. Consequently, it enables digital or low-voltage control circuits to safely switch or sense signals from high-voltage or noisy power circuits. The ‘C’ suffix indicates a high current transfer ratio (CTR) range, meaning the output phototransistor efficiently amplifies the input LED signal, making it a robust choice for various interface applications. Therefore, utilize the EL357N-C to implement secure signal transfer, general purpose switching, and feedback control loops in power electronics.

Key Features:

• High Isolation Voltage: Provides a high isolation voltage rating of 3750 V_RMS, ensuring robust safety and effective separation between input and output stages.
• Compact SOP-4 Package: The Small Outline Package (SOP-4) minimizes the required PCB footprint, making it ideal for high-density, surface-mount designs.
• High Current Transfer Ratio (CTR): The ‘C’ version offers a guaranteed CTR range of 100% to 200%, ensuring high efficiency and low drive requirements for the input LED.
• Fast Switching Speed: Achieves a typical rise time (t_r) and fall time (t_f) of a few microseconds, making it suitable for medium-speed digital signal transmission.
• Lead-Free and RoHS Compliant: Adheres to strict environmental standards, confirming its suitability for modern electronic manufacturing processes.

Technical Specifications:

• Isolation Voltage (V_ISO): 3750 V_RMS minimum
• Collector-Emitter Voltage (V_CEO): 80 V maximum
• Collector Current (I_C): 50 mA maximum
• Input Forward Voltage (V_F): Typically 1.2 V (≤ 1.4 V max)
• Current Transfer Ratio (CTR): 100% to 200% (at I_F = 5 mA, V_CE = 5 V)
• Operating Temperature Range: −55°C to +110°C
• Switching Time (t_r/t_f): Typically 4 μs / 3 μs

Mechanical Specifications:

• Package Type: SOP-4 (Surface Mount Device)
• Lead Finish: Solder Plating (Lead-free)
• Pin Count: 4 Pins
• Case Material: High-grade plastic compound, meeting UL 94 V-0 flammability standards.

Dimensions:

• Body Length: ≈ 4.4 mm
• Body Width: ≈ 4.4 mm
• Pin Pitch (E-to-C): ≈ 2.54 mm
• Overall Height: ≈ 2.1 mm (Low profile for thin designs)

Pinout and Wiring:

• Pin 1 (Anode): Connect to the positive power supply of the input control circuit (requires a series current-limiting resistor).
• Pin 2 (Cathode): Connect to the microcontroller’s output pin or ground to control the LED current flow.
• Pin 3 (Emitter): Connect to the output circuit’s ground or reference potential.
• Pin 4 (Collector): Connect to the positive supply of the output circuit via a pull-up resistor (R_L). The output signal is typically taken from this pin.

Datasheet Reference:

• Download Everlight EL357N Optocoupler Datasheet

Commonly Used in:

• Switch Mode Power Supplies (SMPS): Essential for feedback loops (secondary to primary side isolation) to regulate output voltage.
• Digital Isolation: Bridging communication between microcontrollers and high-power peripherals.
• Communication Interfaces: Isolating RS-232, RS-485, and I²C buses from noise.

Applications:

• DC/DC Converters: Providing isolated voltage sensing and error amplification.
• Motor Control Circuits: Separating the sensitive motor controller logic from the high-current motor drivers.
• I/O Port Isolation: Implementing isolated input channels in Programmable Logic Controllers (PLCs) and industrial controls.
• Battery Monitoring Systems: Safely transmitting status signals from high-voltage battery packs.

Equivalent Models:

• PC817C (Sharp/Socle): A very common and widely cross-referenced phototransistor optocoupler, often used interchangeably, however, verify the package type (DIP vs. SOP).
• LTV-817C (Lite-On): Another industry-standard phototransistor coupler with similar specifications and CTR binning.
• TLP181 (Toshiba): A high-performance miniature SOP-4 coupler with comparable isolation and faster switching speeds.

Package Includes:

• 1 x EL357N-C Phototransistor Opto-Coupler SOP-4