Isolators with on-chip DC/DC make 2W plug-and-play isolated power supplies

April 02, 2015 // By Graham Prophet
Silicon Labs’ Si88xx isolators with on-chip DC-DC converter target industrial applications including factory automation, solar inverters and battery management.

A family of high-speed, multi-channel digital isolators is designed to provide a complete, highly integrated solution for signal and power isolation. Silicon Labs’ Si88xx isolators feature an integrated DC-DC converter with 78% efficiency, deliver up to 2W of power, and offer very low electromagnetic interference emissions and high noise immunity. The Si88xx family is suitable for applications in harsh, noisy operating environments including factory automation, process control, programmable logic controllers (PLCs), solar inverters and automotive battery management.

The isolator family addresses, says Silicon Labs, a critical need in industrial automation for plug-and-play isolated power supplies. Developers often must design made-from-scratch isolated power supplies. Discrete power isolation solutions commonly use FETs, controllers, single-channel isolators or optocouplers, and other components. In contrast, a design based on a multi-channel Si88xx isolator requires the addition of only one miniature ferrite core transformer and a few discrete passive components.

Si88xx digital isolators provide up to 2W of isolated power by harvesting power from the primary side to supply secondary side power. The isolators offer up to four high-speed digital isolation channels with excellent timing characteristics including low propagation delay and low jitter, enabling longer system lifetimes at high voltages. The low-power, high-speed Si88xx digital isolation channels offer useful data rate, propagation delay and reliability advantages over legacy isolation technologies including optocouplers. The Si88xx family supports data rates of up to 100 Mbps, and Si8xx devices achieve typical propagation delays of 23 nsec.

The Si88xx isolators incorporate Silicon Labs’ digital isolator technology with an on-chip isolated DC-DC converter providing regulated output voltages of 3.3V or 5.0V (or over 5V with external components) at peak output power levels of up to 2W. The robust dc-dc converter architecture, coupled with a ferrite core isolated transformer, provides power to self-power the secondary side of the isolator as well as other components such as RS-485 or CAN transceivers, microcontrollers and analogue-to-digital converters. The DC-DC converter is based on a modified