The LTC?4300 series hot swappable 2-wire bus buffers
allow I/O card insertion into a live backplane without corruption
of the data and clock busses. When the connection
is made, the LTC4300-1/LTC4300-2 provide bidirectional
buffering, keeping the backplane and card capacitances
isolated. Rise-time accelerator circuitry* allows the use of
weaker DC pull-up currents while still meeting rise-time
requirements. During insertion, the SDA and SCL lines are
precharged to 1V to minimize bus disturbances.
The LTC4300-1 incorporates a CMOS threshold digital
ENABLE input pin, which forces the part into a low current
mode when driven to ground and sets normal operation when
driven to VCC. It also includes an open drain READY output
pin, which indicates that the backplane and card sides are
connected together. The LTC4300-2 replaces the ENABLE
pin with a dedicated supply voltage pin, VCC2, for the card
side, providing level shifting between 3.3V and 5V systems.
Both the backplane and card may be powered with supply
voltages ranging from 2.7V to 5.5V, with no contraints on
which supply voltage is higher. The LTC4300-2 also replaces
the READY pin with a digital CMOS input pin, ACC, which
enables and disables the rise-time accelerator currents.
The LTC4300 is available in a small 8-pin MSOP package.