Optocouplers have existed in various forms since the late 1960s and find use in many different applications, but they suffer from technical issues and are generally regarded as just “good enough.” In this article, learn about the new generation of pin-compatible digital isolators from Skyworks, designed to be a replacement for outdated optocoupler technology.
21st Century Alternatives to Optocouplers
Developers have long recognized that optocouplers are based on outdated technology, and only recently have cost-effective and easy-to-use alternatives become available. These advanced package-and pin-compatible drop-in optocoupler replacements provide substantially higher performance and reliability with none of the technical liabilities of optocouplers.
For example, the Si87xx digital isolators from Skyworks directly replace 6- and 8-pin optocouplers and are suitable for both optocoupler retrofit and new system designs. They directly connect to existing external optocoupler input circuits, including those that reverse-bias the optocoupler input LED. These devices use a CMOS-based isolation architecture that is ten times more reliable than optocouplers, enabling manufacturers to support longer end-product warranties and reduce costs associated with repairs or replacement. In addition, device operating parameters vary only slightly across voltage and temperature, simplifying system designs since engineers no longer need to account for optocoupler aging effects.
Grail Isolation
The latest generation of CMOS isolators supports isolation ratings as high as 5 kV with compliance to IEC 60747-5-2 including 10 kV surge protection per IEC 60065. These next-generation isolators also meet the requirements of IEC 60950-1, 61010-1, 60601-1 (reinforced insulation) with working voltages up to 1200 V. The strength and reliability of digital isolators like the Si87xx family enable them to be used in a wide range of end applications while withstanding the harshest electrical environments over a continuous period of 60+ years and a -40 ºC to +125 ºC temperature range.
Conclusion
Pin-compatible digital isolators provide an ideal upgrade solution to replace outdated optocouplers. Advanced optocoupler replacements, such as the Si87xx digital isolators, are now available to replace 6- and 8-pin optocouplers, connecting directly to existing external optocoupler input circuits, including designs that reverse-bias the anode input. These optocoupler replacements are useful in both new and retrofit applications, offer more than 10x higher reliability than optocouplers, use less power, and provide faster and more uniform timing performance. Put simply, modern optocouplers cannot match the performance and reliability of the latest generation of CMOS isolators.