Isolating I2C Interfaces:The Inter-Integrated Circuit (I2C?) bus is a two-wire bidirectional bus used for low speed, short-distance communication between integrated circuits. Developed by Philips1 in the early 1980s for use amongst ICs on a single board, I2C today is increasingly being used in multiboard applications as new bus extensions and control devices help overcome the original 400 pF maxi- mum allowable load capacitance.Often, in multicard applications such as blade servers or digitally-controlled power converters, it is desired that each interface be isolated to allow for trouble-free card insertion/removal or for safety considerations. However, isolating I2C interfaces is complicated by the bidirectional
nature of the I2C bus. This characteristic is not compatible
with the unidirectional behavior of optocouplers. This application note provides a brief overview of the I2C bus (focusing on its physical layer), discusses the challenges in isolating I2C interfaces, and describes iCoupler? solutions for isolating I2C interfaces.