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TS5A23166: Voltage at VCC when NO powered but VCC disconnected

Part Number: TS5A23166

Hi, I have a board with multiple TS5A23166 switch ICs being used to isolate a UART BUS. Each one is powered separately from a 3V3 source that may be on or off  (device present or not). I chose the TS5A23166 as it should not back power these supplies when they are powered off and to allow me to switch in a single UART to be on the BUS.


When I apply 3.3V through a 1K resistor from an FTDI cable to the BUS TX or RX (NO1/2) all of the LEDs light up and I am reading around 1.8V on the LOCAL_3V3_x lines. 

The reason I chose this IC was to avoid back powering the devices on the LOCAL supplies and to have 

What is going on and why is this happening please?