TPS62823: TPS62823. MY output voltage is always 0.2V lower than input voltage, not 1.8v.

Part Number: TPS62823

I am trying TPS62823. 

The attachment is my testing board.

I connect SYS and EN to positive on my power supply, GND_TPS and AGND to negative on my power supply. 

Output - VCC_TPS is always 0.2V lower then input - SYS. When sys is 5V, VCC_TPS is 4.8V, sys is 4V, VCC_TPS is 3.8V.

Furthermore, when I remove EN, only connect sys on positive. When the input is 5V, the output is 3.4V.

Very strange.

Thanks