Hi, I use the PCA9745B on a shared SPI bus system with other three non PCA9745B devices in parallel.
Problem: The SDO output signal goes not in the high-impedance state when /CS is high like described in the datasheet section 8.1 :
"8.1 SPI-compatible 4-wire serial interface signals
CS — The active LOW chip select line is used to activate and access the SPI slaves. As
long as CS is HIGH, all slaves will not accept the clock signal or data, and the output SDO
is in high-impedance state. Whenever this pin is in a logic LOW state, data can be
transferred between the master and all slaves."