Drop-in digital isolators replace optocouplers

Silicon Laboratories Inc. has introduced the industry's first drop-in replacement for optocouplers based on mainstream CMOS technology and incorporating an LED emulator input.

The Si87xx digital isolators are aimed at 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.

Silicon Labs’ Si87xx opto-replacement devices use a patented CMOS-based isolation architecture that is immune to the output variations that 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

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 and 60601-1 (reinforced insulation) and provides up to 1200 V working voltage with a 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 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.

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 (USD).

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.

Datasheet: Click here.