Fast dual bidirectional bus buffer with hot insertion logic
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The PCA9522 is a monolithic bipolar integrated circuit for bus buffering in applications including I²C-bus, SMBus, etc. It includes hot insertion logic for detecting stop and idle conditions, making it ideal for live insertion into backplanes. The buffer extends the busload limit by buffering both the SCL and SDA lines. The PCA9522 is a drop-in replacement for the IES5502, with only the maximum bus voltage reduced from 15 V to 10 V.
Hot insertion logic allows the IC to be plugged into live backplanes without causing data corruption on the bus. The open-collector ready signal (RDY) indicates when the connection has been made. Precharging of the backplane ports minimizes disruptions to the bus during hot insertion.
The enable function allows sections of the bus to be isolated. Individual parts of the system can be brought on-line successively. Bus level translation between a very wide range of bus voltages, from 1.8 V to 10 V, is supported. These features provide enormous flexibility in interfacing systems of different technologies, operating speeds and loads.
The operation of the PCA9522 provides one of the fastest response times of such bidirectional buffers. It does this without the need for rise-time accelerators which, combined with low noise margins, may cause glitches outside of the I²C-bus specification.