The LTC4309 is a hot-swappable 2-wire bus buffer that allows I/O card insertion into a live backplane without corruption of the data and clock buses. It provides bidirectional buffering, keeping the backplane and card capacitances isolated. Low offset and high VOL tolerance allow cascading of multiple devices on the clock and data buses. 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 buses will remain connected with no clock or stop bit generation. ACC input enables rise-time accelerators for high capacitively loaded buses. During insertion, the SDA and SCL lines are precharged to 1V to minimize bus disturbances. When driven high, the ENABLE input allows the LTC4309 to connect after a stop bit or bus idle. Driving ENABLE low breaks the connection between SDAIN and SDAOUT, SCLIN and SCLOUT. READY is an open drain output which indicates that the backplane and card sides are connected.
The LTC4309 is a hot‑swappable 2‑wire bus buffer that enables live board insertion without corrupting I²C/SMBus data and clock lines. It provides bidirectional buffering, low offset, and optional bus‑disconnect and recovery features. The device pre‑charges SDA and SCL lines to 1 V during insertion and can generate up to 16 clock pulses and a stop bit to free a stuck bus.
The part is offered in a 12‑lead DFN (4 mm × 3 mm) and a 16‑lead narrow‑profile SSOP package. It supports supply voltages from 0.3 V to 6 V, offers up to +6 kV HBM ESD protection, and includes rise‑time accelerators that can be enabled via the ACC pin for faster bus transitions.
| Supply Voltage (VCC) | 3.3 V |
|---|---|
| ESD Ruggedness (HBM) | +6 kV |
| Package Options | 12‑lead DFN (4 mm × 3 mm) and 16‑lead SSOP |
During insertion the device pre‑charges SDA and SCL lines to 1 V, isolates the bus, and prevents data corruption while the backplane powers up.
The part is offered in a 12‑lead plastic DFN (4 mm × 3 mm) and a 16‑lead narrow‑profile SSOP package.