Silicon Labs CMOS-based Si87xx isolators offer longer device life and reliability


Enables manufacturers to extend product warranties

Click image to enlarge: Silicon Labs Si87xx isolators

Silicon Laboratories has introduced drop-in replacement for optocouplers. Based on mainstream CMOS technology and incorporating an innovative LED emulator input, the new Si87xx digital isolators offer a pin configuration, package, and footprint match for a number of optocoupler products. Offering superior noise immunity, more robust performance, and greater reliability makes the Si87xx isolators well suited for solar power inverters, SMPS, UPS, industrial drives, PLCs, and high-voltage medical equipment. Optocouplers, used for more than 40 years, are inherently limited by outdated LED-based technology, that exhibits significant output variation over input current, temperature, and age. The 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 ageing 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 opto-replacement devices use a patented CMOS-based isolation architecture that is completely immune to the output variations that plague LED-based optocouplers. CMOS-based capacitive isolation technology provides more than 10x the 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 ageing 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 60+ year lifetime. In addition to their inherent immunity to temperature, age, and forward current effects, the Si87xx isolators offer other significant performance advantages over competing optocouplers:

  • The Si87xx devices offer a 50% 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 CMTI (common mode transient immunity) by as much as 75% 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.
All Si87xx isolators incorporate an innovative LED emulator input that, along with new package options, allows Silicon Labs to offer a fully drop-in compatible upgrade for many existing optocouplers. The base Si8710 device consists of an LED emulator input and an open-collector output. Two additional device configurations are available: the Si8711 adds an integrated pull-up resistor, and the Si8712 includes a dedicated enable pin that can asynchronously control the output. Pricing and Availability Samples and production quantities of the Si87xx digital isolators are available now in SOIC-8 and GW DIP-8 packages with isolation ratings up to 3.75 kV. Si87xx products in SO-6 and LGA-8 packages certified to 5 kV isolation ratings will be available in Q1 2013. Pricing for the new Si87xx digital isolators in 10,000-unit quantities begins at $0.43 . The Si87xxDIP8-KIT Evaluation Kit, available now for $29 (USD MSRP), enables customers to evaluate the performance of Si87xx opto-replacement isolators. The evaluation board is flexible enough to allow both hook-up to lab equipment for detailed specification evaluation as well as connection to the customer's existing board. Silicon Labs Isolation products deeplink