The TLP283 is a compact photocoupler (optocoupler) developed by Toshiba. By combining a gallium-arsenide infrared LED with a phototransistor, it provides electrical isolation between circuits, making it especially valuable in power supplies, I/O boards, and industrial control systems. Although the TLP283 has been discontinued in newer production runs, it is still widely discussed in electronics communities and serves as a great reference for optocoupler design.
Key Features
The TLP283 offers strong isolation with a rating of around 2500 Vrms, protecting low-voltage circuits from high-voltage environments. Its collector-emitter voltage can reach 100V, ensuring safe operation in demanding applications. The current transfer ratio (CTR) typically starts at 100% when driven with 1mA input current, and it can scale up significantly depending on circuit requirements. The maximum forward current is about 50mA, with the ability to handle short pulse currents of up to 1A. Switching speed is modest, with delays within the 100µs range, making it suitable for many industrial and consumer-level systems but less ideal for high-speed digital communication. The operating temperature range spans from –55°C to +100°C, supporting use in harsh environments.
Why Use the TLP283?
Optocouplers like the TLP283 provide galvanic isolation, which separates the control side of a system from the high-power domain. This not only protects sensitive microcontrollers but also ensures system safety in case of surges or spikes. The TLP283’s compact SOP-4 package makes it convenient for surface-mount PCB designs, saving board space while maintaining functionality. It also offers strong noise immunity, a key advantage in industrial and switching power supply circuits.
Typical Applications
The TLP283 has been widely used in circuits where isolation and reliability are critical. Designers implement it in microcontroller interfaces, ensuring safe signal transfer between low-voltage logic and high-voltage loads. It finds a place in switching power supplies, AC adapters, and programmable logic controllers (PLCs). Additionally, it has been used in office automation equipment, industrial drivers, and signal input/output boards. Its durability makes it suitable for both consumer electronics and heavy-duty industrial machinery.
Design Considerations
When designing with the TLP283, engineers usually include an input resistor to regulate LED current, ensuring proper operation without exceeding forward current limits. The switching delay must also be considered, especially in timing-sensitive circuits. For applications in hotter environments, derating the LED current is recommended to maintain long-term reliability. Since the TLP283 is now classified as obsolete, new designs may prefer modern replacements with improved switching speeds and extended availability. However, for maintaining or repairing existing systems, the TLP283 remains a dependable choice.
Example: Driving with Arduino
A common educational example involves using an Arduino to drive the LED input of the TLP283, isolating it from a higher voltage load. By toggling an Arduino output pin, the optocoupler activates a transistor on the output side, allowing safe and isolated control of motors, relays, or AC circuits.
const int inputPin = 7;
void setup() {
pinMode(inputPin, OUTPUT);
}
void loop() {
digitalWrite(inputPin, HIGH); // Activate optocoupler
delay(1000);
digitalWrite(inputPin, LOW); // Deactivate
delay(1000);
}
This demonstrates how an optocoupler serves as a simple bridge between logic-level signals and higher voltage systems without direct electrical contact.
Conclusion
The TLP283 optocoupler is a versatile isolation component that has proven its value across industrial and consumer applications. Its combination of compact design, high isolation voltage, and stable CTR made it a popular choice in legacy designs. While modern replacements are recommended for new projects, understanding the TLP283 provides a solid foundation for anyone learning about optocouplers and their role in safe circuit design.
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