Hot swap two-wire bus buffer

Linear Technology has introduced the LTC4301, a supply independent, hot-swappable two-wire bus buffer that allows I/O card insertion into a live backplane without corruption of the bus data (SDA) and clock (SCL) lines.

The IC provides capacitive isolation between the backplane and the card’s I²C busses, even if their respective supplies are at different levels. Without compromising the I²C threshold levels, the supply independent feature eliminates the need to dedicate a connector pin for the backplane supply voltage, said the firm.

The SDA and SCL pins can withstand 8kV ESD, thus protecting the card from damage due to handling.

The device provides capacitive buffering for I²C busses connected across the backplane. As a result, the backplane bus sees only the capacitance of the buffer ICs, about 10pF each, instead of the entire cards’ bus capacitance. This increases the number of nodes that can be supported in a given system and helps eliminate signal integrity problems.

During insertion, the LTC4301 pre-charges the SDA and SCL lines to 1V to minimize bus disturbance. Control circuitry prevents the backplane from being connected to the card until a stop bit or a bus idle is present. The READY output pin indicates that the backplane and card sides are connected together.

The LTC4301 is offered in commercial and industrial temperature ranges. Pricing begins at $1.95 each for 1,000-piece quantities.