The DRV835x family of devices provides a separate sense and reference pin for the common point of the high-side MOSFET drain. This pin is called VDRAIN. This pin allows the sense line for the overcurrent monitors (VDRAIN) and the power supply (VM) to stay separate and prevent noise on the VDRAIN sense line.
The VDRAIN pin serves as the reference point for the integrated charge pump. This makes sure that the charge pump reference stays with respect to the power MOSFET supply through voltage transient conditions.
Since the charge pump is referenced to VDRAIN, this also allows for VM to supplied either directed from the power MOSFET supply (VDRAIN) or from an independent supply. This allows for a configuration where VM can be supplied from an efficient low voltage supply to increase the device efficiency. On the DRV8350R and DRV8353R devices, the integrated buck regulator can be used to create the efficient low voltage supply.