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Linear Tech bus buffer does not compromise I?C threshold levels

Posted: 07 Jun 2004 ?? ?Print Version ?Bookmark and Share

Keywords:linear technology? bus buffer? ltc4301?

Linear Technology Corp. has introduced a supply independent, hot-swappable 2-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 LTC4301 IC provides capacitive isolation between the backplane and the card's I?C busses, even if their respective supplies are at different levels. Without compromising the I?C threshold levels, the supply independent feature eliminates the need to dedicate a connector pin for the backplane supply voltage.

The LTC4301's SDA and SCL pins withstand 8kV ESD, protecting the card from damage due to handling. According to Linear Tech, the device greatly simplifies the task of using a 2-wire bus to manage a large number of cards with different supply and bus voltage levels in a network server, desktop PC or telecom environment.

When I?C is distributed over a backplane, each individual card contributes to the whole system bus capacitance, making rise and fall time requirements difficult to meet. The company point out that the LTC4300 family addresses this problem by providing capacitive buffering for I?C 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.

During insertion, the device 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.

Housed in 8-pin MSOP and DFN packages, the LTC4301 is offered in commercial and industrial temperature ranges, with pricing starting at $1.95 each for 1,000-piece quantities.

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