I2C bus buffer with hot-swap — what it does on the board
The LTC4309IDE#PBF from Analog Devices is a two-channel I2C bus buffer and accelerator designed for hot-swap applications. It sits between a live backplane and a plug-in card, isolating bus capacitance and preventing data corruption during insertion or removal. The part operates from a 2.3 V to 5.5 V supply, drawing 7 mA typical, and supports standard I2C data rates up to 400 kHz (Fast Mode). Its 10 pF input capacitance keeps the bus load light on the upstream controller side.
Hot-swap sequencing and bus isolation
The device detects a valid bus voltage on its supply pin before connecting the upstream and downstream bus segments. This prevents glitches and stuck buses when a card is plugged into a live system.
Package and board layout notes
Housed in a 12-lead WFDFN with exposed pad (4x3 mm DFN), the part requires a surface-mount footprint with a thermal via pattern under the pad for heat sinking.
Lifecycle and sourcing posture
The LTC4309IDE#PBF carries an Active product status with ROHS3 compliance.