Low Offset Bus Buffer

15th July 2007

ES Admin

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Linear Technology has introduced the LTC4307, an I2C bus buffer with low offset and stuck bus recovery that significantly increases the reliability of systems utilizing the I2C bus. With the growth in the number and complexity of plug-in boards, the addition of each new device adds to already accumulated offset voltages and can result in exceeded valid logic low specification. The LTC4307 adds only 50mV of logic low offset voltage between input and output, instead of the typical 100mV or more, allowing users to cascade several LTC4307's in series, while meeting VOL levels and maintaining large noise margins.

As a result, larger systems can be divided into many smaller, less capacitive, and therefore faster bus segments. The low offset feature of the LTC4307 makes it ideal for high availability systems, such as AdvancedTCA and µTCA based servers and networking equipment, which require large I2C busses for critical system management functions.

The LTC4307 also features stuck bus recovery circuitry that helps maintain system integrity by detecting and clearing stuck busses. If the serial data output SDAOUT or serial clock output SCLOUT are low for more than 30ms, the LTC4307 will automatically break the data and clock bus connections and will generate up to sixteen clock pulses on the SCLOUT in an attempt to free the bus. When the bus becomes free, a connection will be immediately enabled for a proper operation to resume, and in essence the LTC4307 will effectively eliminate the need for a general system reset. Furthermore, the LTC4307 provides capacitive isolation between the backplane and the card's I2C busses, even if their respective supplies are at different levels. Since the 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 voltage is not required. In addition to facilitating live card insertion or removal, the SDA and SCL pins withstand ±8kV ESD, providing extra ruggedness and protecting the cards from damage due to handling.

The rich feature set of the LTC4307 makes it well suited for advanced computing, networking and data storage systems that utilize a large number of I/O cards with different supply and bus voltage levels. The LTC4307 is available in 8-lead MSOP and 3mm x 3mm DFN packages. Specified over the commercial and industrial temperature ranges, pricing begins at $2.15 each for 1,000-piece quantities.