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TCA9548A: TCA9548A: Design help

Part Number: TCA9548A
Hi all,

I'm using TCA9548A as the I2C switch in my design.

My main I2C is 3V3. and the secondary side i need to control multiple voltage of I2C device .such as 3v3 & 1v8
I saw that the switch structure inside the IC is a MOS switch. 

Logically, the voltage on the secondary side should not be higher than that on the primary side.

It should be able to operate normally, and it is also written in the data sheet that it can be used in this way.

But when I used it, I found that when I switch the channel to SD2/SC2 ,which i want to control 1V8 device ,

even if the secondary was not connected to any other device,

there would still be a 2.xv voltage on it, which would cause my 1v8 device to be abnormal.

In the picture in red.

Please help to confirm whether there is any design abnormality. 

Thanks.