Isolators with on-chip DC/DC make 2W plug-and-play isolated power supplies
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 fly-back architecture with secondary side sensing and feedback to the controller with external compensation. The power switches use zero voltage switching (ZVS) techniques to minimise power losses as well as dithering to minimise EMI.
The Si88xx isolators incorporate multiple safety features including a built-in soft-start function providing protection from inrush currents, a cycle-by-cycle current limiting capability and thermal detection/shutdown. The integrated DC-DC converter includes a built-in secondary sensing and feedback signal, eliminating the need for an additional opto feedback path while enabling excellent line and load regulation for greater system stability. The DC-DC converter also features a shut-down option and user-adjustable switching frequency for fine-tuning the EMI profile to suit each developer’s application needs.
In 20-pin WB SOIC packages, options include a choice of DC-DC converter features, isolation channel configurations and a fail-safe mode. All Si88xx products are certified by UL, CSA, VDE and CQC. Si88xx family pricing begins at $2.42 (10,000). Silicon Labs’ Si88xxxISO-KIT evaluation kit is available now for $29.
Silicon Labs; www.silabs.com/Si88xx
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