Silicon Lab set to make optocouplers obsolete with new drop-in digital isolators

Silicon Laboratories has introduced a drop-in replacement for optocouplers that is based on mainstream CMOS technology and incorporates a light-emitting diode (LED) emulator input. The new Si87xx digital isolators offer a pin configuration, package and footprint fit that is suitable for a number of optocoupler products.

These new devices offer noise immunity, a more robust performance and greater reliability, according to the company, making them suitable for solar power inverters, switched mode power supplies (SMPS), uninterruptible power supplies (UPS), industrial drives, programmable logic controllers (PLCs), high-voltage medical equipment and other applications that often use optocouplers.

Optocouplers have been in use for over 40 years but are inherently limited by outdated LED-based technology, which exhibits significant output variation over input current, temperature and age. These variations reduce the operating performance and reliability over the optocoupler’s lifetime, resulting in increased design complexity and shorter life expectancy for end products. Because of their aging effects, optocouplers are often specified to last only 10 years, posing a serious problem for industrial system designers who want to develop products with 20+ year warranties.

The Si87xx opto-replacement devices use a patented CMOS-based isolation architecture that is immune to the output variations that tend to plague LED-based optocouplers. CMOS-based capacitive isolation technology provides more than ten times the mean-time-to-failure (MTTF) rate of optocouplers. By offering longer device lifetimes and higher reliability, the Si87xx isolators enable system manufacturers to support longer end product warranties and reduce costs associated with repair or replacement. Less variability, especially in the input turn-on current, also simplifies system designs since engineers no longer need to anticipate aging effects when using the Si87xx devices.

The Si87xx family is based on Silicon Labs’ capacitive isolation technology, with isolation ratings up to 5 kV and fully compliant with IEC 60747-5-2 including 10 kV surge protection. The family meets the requirements for IEC 60950-1, 61010-1, 60601-1 (reinforced insulation) and provides up to 1200 V working voltage with a 60+ year lifetime.

The Si87xx isolators are also able to offer a 50 percent lower input turn-on current and a 10x lower output quiescent current than competing optocouplers, reducing overall system power and the low parasitic capacitance of the Si87xx digital isolation architecture helps to improve the common mode transient immunity (CMTI) by as much as 75 percent over competing optocouplers, thereby enhancing system data integrity.

“The new Si87xx family represents the industry’s first major step along the path to drop-in optocoupler replacement by providing a package/footprint fit for a number of widely used optocoupler products,” said Mark Thompson, vice president and general manager of Access, Power and Sensor products at Silicon Labs. “Our new opto-replacement solution is the best choice for systems that currently use outmoded optocouplers but need significant improvements in power efficiency, performance, reliability and product lifetime.”


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