Linear lines up bus buffers for stuck bus recovery

Oct. 27, 2005
Two new ICs overcome stuck bus limitations by isolating all bus connections on the upstream side while restoring the downstream bus.

Linear Technology has introduced the LTC4303 and LTC4304 2-wire bus buffers with stuck bus recovery. These ICs solve the common problem of a stuck bus by isolating all of the bus connections on the upstream side, while restoring the downstream bus.

If the serial data output SDAOUT or serial clock output SCLOUT are low for more than 30ms, the LTC4304 will automatically break the data and clock connections, issuing a Fault signal. Sequentially, the LTC4304 will automatically generate up to 16 clock pulses on the SCLOUT in an attempt to free the bus. When the bus becomes free, a connection is immediately enabled and proper operation resumes. The LTC4303 and LTC4304 don’t need a general system reset and unburden the microcontroller, providing the appropriate signals to free the bus.

The ICs provide capacitive isolation between the backplane and the card's I2C buses, even if their respective supplies are at different levels. They perform this level translation without a second supply pin or a second pair of input pull-up resistors; there is no need for a dedicated connector pin for the backplane supply voltage.

Due to the use of capacitive buffering, the backplane bus sees only the capacitance of the buffer ICs, about 10pF each, instead of seeing the entire cards' bus capacitance. This increases the number of nodes that can be supported in a given system and eliminates most signal integrity problems.

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