The LTC4309 hot swappable 2-wire bus buffer allows I/O card insertion into a live backplane without corruption of the data and clock busses. The LTC4309 provides bidirectional buffering, keeping the backplane and card capacitances isolated. Low offset and high VOL tolerance allows cascading of multiple devices on the clock and data busses. If SDAOUT or SCLOUT are low for 30ms, FAULT will pull low indicating a stuck bus low condition. If DISCEN is tied high, the LTC4309 will automatically break the bus connection and generate up to 16 clock pulses and a stop bit in an attempt to free the bus. A connection will resume if the stuck bus is cleared. If DISCEN is connected to GND, the busses will remain connected with no clock or stop bit generation. ACC input enables rise-time accelerators for high capacitively loaded busses.