In datasheet ADP7182，it said ‘’The exposed pad is electrically connected to VIN inside the package. and must be connected to the VIN plane on the board for proper operation‘.
But I tested the chip and found they are not connected.
Why？ And in my PCB，exposed Pad is not connected to any net . Is there any problem for noise or other performance?
The same question is for ADM7151. Is the exposed pad must connected to ground?
The reason why you are not seeing a hard short between VIN and EPAD is because the conductive material between the EPAD and substrate is not really low impedance. For proper operation of the ADP7182, the EPAD must be connected to VIN.
One of the most importance function of the exposed pad is to dissipate the heat from the IC, thus is is recommended to connect it to the lowest potential which is "VIN" for ADP7182 and "GND" for ADM7151.