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Low-offset buffer improves I2C reliability

Milpitas, Calif.&#8212Linear Technology's LTC4307 is an I2 C bus buffer with low offset and a “stuck bus” recovery feature designed to significantly increase system reliability.

The addition of each new device to a plug-in board adds to the accumulated offset voltage and can result in exceeding the valid logic-low specification. The LTC4307 adds just 50 mV of (logic-low) offset voltage between input and output, versus the typical 100 mV or more, and thus it's suited for high availability systems, such as AdvancedTCA and TCA based servers and networking equipment, which generally require large I2 C buses. Users can also cascade several LTC4307's in series for bus expansion, thus allowing the designer to effectively divide the system into many smaller, less capacitive (and therefore faster) bus segments.



The LTC4307 “stuck bus” recovery circuitry basically eliminates the need for a general system reset. If the serial data output SDAOUT or serial clock output SCLOUT are low for more than 30 ms, the LTC4307 will automatically break the data and clock bus connections and generate up to sixteen clock pulses on the SCLOUT in an attempt to free the bus. Normal operation resumes once the bus condition is cleared.

The LTC4307 also provides capacitive isolation between the backplane and the card's I2 C buses, even if their respective supplies are at different levels. Level-translation is performed without a second supply pin or a second pair of input pull-up resistors; a dedicated connector pin for the backplane supply is not required. In addition to facilitating live card insertion or removal, the chip, via its SDA and SCL pins, provides ±8 kV ESD protection for extra ruggedness.

Click here for the product datasheet. The LTC4307 is available in 8-lead MSOP and 3-by-3 mm DFN packages. Specified over the commercial and industrial temperature ranges, it's priced beginning at $2.15 each in 1k pieces.

Linear Technology , 1-800-4LINEAR, www.linear.com

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