Method provides fast, glitch-free isolation of [I.sup.2]C and SMBus signals.(design ideas)

EDN, June, 2004 by Thoren, Mark

[I.sup.2]C IS A POPULAR SERIAL protocol for power controllers, ADCs and DACs, EEPROMs, and other devices. In certain data-acquisition and power-control situations, you must isolate the [I.sup.2]C master from one or more slave de vices for noise, grounding, or safety issues. Also, although 128 peripherals may connect to the bus, at some point, differences in ground potential and excessive bus capacitance begin to erode noise and timing margins. This Design Idea shows how to provide fast, glitch-free optical isolation of [I.sup.2]C or SMBus signals by using a method that meets the requirements for the 400-kHz enhanced-[I.sup.2]C-bus specification. The FC bus consists of bidirectional clock and data lines (SCL and SDA) that are pulled up with resistors or current...

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