Digital isolators for consumer product designs and T&M

July 01, 2014 // By Graham Prophet
Silicon Labs’ isolators outperform optocouplers, the company says, for household appliance applications requiring multi-channel 1 kV functional isolation.

These digital isolators are positioned by Silicon Labs as offering the highest channel count, performance, reliability and data rates for cost-sensitive consumer electronics applications requiring functional isolation of up to 1 kV. Based on Silicon Labs' CMOS-based digital isolation technology, the Si80xx family provides a superior alternative to optocouplers for household appliances, as well as test and measurement equipment requiring functional isolation.

The Si80xx digital isolator architecture incorporates a transmitter and a receiver separated by a CMOS-based isolation barrier. The Si80xx isolators use a high-frequency internal oscillator on the transmitter to modulate digital input signals across the capacitive isolation barrier. On the receiver side, these signals are demodulated back to the corresponding digital output signals, which are electrically isolated from the input. This architecture provides a robust data path requiring no special considerations or initialisation at start-up. The transmitter consists of an input stage that latches in data from up to six asynchronous channels, followed by a serialiser stage where the data is compressed into serial data packets coupled across the capacitive isolation barrier. The receiver consists of a demodulator block that converts the modulated signal back into serial data packets that are deserialised and latched to the output.

The Si80xx isolators deliver 10 Mbps data rates across a wide temperature range (-40 to 125 ºC), as well as low power operation of approximately 2 mA per channel (5x lower than optocoupler alternatives) for energy-efficient system design. The Si80xx family’s robust digital isolation architecture ensures that signal integrity is maintained even while operating at high data rates and at high temperatures in harsh environments.

Optocouplers are known to be subject to output variations over input current, temperature and age. These variations reduce the operating performance of optocouplers over their lifetime, causing increased design complexity and reduced product reliability. Silicon Labs’ Si80xx digital isolators overcome these limitations through capacitive isolation based on mainstream CMOS process technology. Higher reliability and longer device