Other Parts Discussed in Thread: TCA6408A, , TCA9548A
I am having the same problem as "user4646208": No ACK (SDA is high on ACK clock pulse) from a TCA6416A as well as a TCA6408A device.
Both devices are connected to a TCA9548A I2C switch and the port pins of the switch (the SCL and SDA pins of the I2C expanders) are active and sending out the correct write sequence. A third I2C device connected to the same switch (Si7021 thermometer from Silicon Devices) is accessed in the same manner and is providing a valid acknowledge (ACK low) on the SDA line.
Below is the schematic of the I2C expanders. The power supply voltages are verified and the chips are properly soldered. I can provide O-scope pictures if needed, but they are essentially identical to the ones "user4646208" provided in his post.