Easy Drop-in Replacement for Optocoupler Solutions
The Si87xx digital isolator family is available in popular optocoupler configurations shown below, and most applications require no PCB modification — simply install the Si87xx into the optocoupler footprint (package options include SOCI8, DIP8, LGA8 and SDIP6). The Si87xx series feature are open drain outputs. Any external components used to improve optocoupler common mode transient immunity (CMTI), such as "speed-up" capacitors, negative voltage supplies and input buffers can be left intact or removed to reduce external BOM.
Optocoupler Replacement Technology
Used for more than 40 years, optocouplers are inherently limited by outdated LED-based technology, which exhibits significant output variation over input current, temperature and age.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.
Silicon Labs’ Si87xx optocoupler-replacement devices use a patented CMOS-based isolation architecture that is completely immune to the output variations that plague LED-based optocouplers. The innovative light-emitting diode (LED) emulator input included in the Si87xx devices eliminates the need to redesign existing systems.
Reliability over Time and Temperature
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’ industry-leading 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 and 60601-1 (reinforced insulation) and provides up to 1200 V working voltage with a 60+ year lifetime. The wide -40 to +125 °C operating range makes the Si87xx the perfect optocoupler replacement in high temperature applications such as solar inverters.
The Si87xx products are CSA
The Si87xx products are VDE
Performance Enhancements over Optocoupler Solutions
In addition to their inherent immunity to temperature, age and forward current effects, the Si87xx isolators offer other significant performance advantages over competing optocoupler solutions:
- The Si87xx devices offer a 50 percent lower input turn-on current and a 10x lower output quiescent current than competing optocouplers, reducing overall system power.
- The low parasitic capacitance of the Si87xx digital isolation architecture improves the common mode transient immunity (CMTI) by as much as 75 percent over competing optocouplers, thereby enhancing system data integrity. Due to the inherent high parasitic capacitance of their LED-based architecture, optocouplers suffer from poor CMTI, which can lead to incorrect data being passed across the isolator.
- The Si87xx isolators outperform optocouplers in key timing specifications, such as propagation delay and pulse-width distortion, enabling faster, more accurate data transfer and improved efficiency.