Op to couplers, also known as op to-isolators, are components that transfer electrical signals between two isolated circuits by using infrared light. As an isolator, an op to coupler can prevent high voltages from affecting the side of the circuit receiving the signal. Transferring signals over a light barrier by using an infrared light-emitting diode and a light-sensitive product, such as a phototransistor, is the main structure of an op to coupler. On the first page, datasheets provide the main product description, its features, suggested areas of applications, ordering information, and agency approvals, as shown in Figure 1 for the VO617A op to coupler with phototransistor output. Following pages provide key technical specifications, operating conditions, and graphs showing the behavior of the product.
Datasheets generally begin with a header stating the product’s name, which is followed by a graphic representation of the package and symbol. Key features follow, with a list of the most popular applications and available safety agency approvals. An example has been given in Figure 1, which shows the introduction page for the VO617A.
In general, all datasheets contain the following information:
- Agency approvals
- Ordering information
- Absolute maximum ratings
- Electrical characteristics
- Current transfer ratio (CTR)
- Switching characteristics
- Safety and insulation ratings
- Typical static graphs
- Typical dynamic graphs
- Packaging dimensions, markings, and packaging
Description, features, applications, and agency approval information
The description will introduce the product, the main product category, the technology used, and its features. Special specifications such as high operating temperature, high current transfer ratio, and low coupling capacitance are identified to give an overview. The application section introduces the most common applications using the component. The agency approvals section provides an overview of the product’s approvals to different standards and agencies. Above the description, a symbol and selection of package types are shown.
Op to couplers are available in many different packages and configurations. One typical symbol that can be found — an infrared diode and a phototransistor together in a 4-pin package — is shown in Figure 2. Figure 2 also highlights the different packages in which the VO617A is available. The first is the DIP 4 (dual in-line package), which is connected through the PCB. The others are SMD packages with different bending options to the pins. They are populated on the top of the PCB.
Read More: Guidelines for reading an op to coupler datasheet