Isolating digital data from high voltage has traditionally been the role of optoelectronics or other isolation techniques that include giant magnetoresistors, pulse transformers or galvanic isolators. The limitations of the optoelectronics, one of the lowest-cost approaches, includes a limited data rate of 10 Mbps or less, performance degradation at a higher temperature, and only a single channel per 8-pin package. Using RF technology, Silicon Laboratories designed an isolating technique that offers improvements over these competing techniques, especially the optoisolators.
Instead of using light, the Si844x channel modulates an RF carrier. A single, 16-pin wide-body SOIC contains four RF isolators that have a maximum isolation voltage of 2500 VRMS. The design uses a chip-scale transformer fabricated in a standard CMOS process and an RF encoding/decoding technique. Using a 2.1 GHz carrier frequency, the isolator modulates and decodes logic 1's and logic 0's at a rate of up to 150 Mbps with a propagation delay of less than 10ns. When operating at 100 Mbps, each channel consumes less than 12 mA.
In addition to performance advantages, the integration of four isolators in a single package provides a function that is three times smaller than the optocoupler approach, which can reduce the bill of material costs by as much as 50 percent.
Units comply with UL, CSA and VDE electrical standards. Target applications include switch mode power supplies, isolated analog data acquisition, motor control, plasma TVs, Ethernet/CAN networks and isolated point-to-point communications.
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 High Speed Data Isolation
RF encoding and decoding of a 2.1 GHz frequency signal provides up to 2500 VRMS of isolation and data transfer rates as high as 150 Mbps. Click here for a larger image.
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For more information about Silicon Laboratories Si844x digital isolators, visit http://rbi.ims/ca/4924-500.
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