The LTC4310 provides bidirectional I2C communications between two I2C buses whose grounds are isolated from one another. Each LTC4310 encodes I2C bus logic states into signals that are transmitted across an isolation barrier to another LTC4310. The receiving LTC4310 decodes the transmission and drives its l2C bus to the appropriate logic state. The isolation barrier can be bridged by an inexpensive Ethernet, or other transformer, to achieve communications across voltage differences reaching thousands of volts, or it can be bridged by capacitors for lower voltage isolation. The LTC4310-1 is intended for use in 100kHz I2C systems. The LTC4310-2 is intended for 400kHz I2C systems. Rise time accelerators provide strong pull-up currents on SCL and SDA rising edges to meet rise time specifications for heavily loaded systems. Data and clock Hot SwapTM circuitry prevent data corruption when a card is inserted into or removed from a live bus. When a bus is stuck low for 37ms, the LTC4310 turns off its pull-down devices and generates up to sixteen clocks and a STOP bit in an attempt to free the bus. Driving EN low sets the LTC4310 in a very low current shutdown mode to conserve power.