The CA9511 is a hot-swappable I²C bus buffer designed to allow safe insertion of I/O cards into a live backplane without corrupting data or clock signals. Its internal control logic ensures that the backplane I²C lines (IN) are not connected to the card-side lines (OUT) until a STOP condition or an idle state is detected, preventing any bus contention.

Once safely connected, the device provides bidirectional buffering that isolates the capacitance of the backplane and the card, improving signal integrity. During insertion, SDA and SCL are pre-charged to 1 V to reduce inrush currents caused by parasitic capacitance. The CA9511 can enter a low-power shutdown mode when EN is low, and return to normal operation when EN is high.

An open-drain READY output indicates whether the backplane and card sides are currently linked. Additional features include rise-time accelerators, compatibility with I²C Standard-mode, Fast-mode and SMBus, support for clock stretching and multi-master arbitration, and operation from 2.7 V to 5.5 V. It is available in SOP-8 and MSOP-8 packages, making it ideal for servers and telecom systems.