The device enters UVLO if the L+ voltage falls below V(UVLO). (For the device without the integrated LDO, the device monitors VCC_IN in addition to L+. UVLO happens if either supply falls below the threshold.)
As soon as the supply falls below V(UVLO), NFAULT is pulled low, the LDO is turned off and the CQ output is disabled (Hi-Z). Receiver performance is not specified in this mode.
When the supply rises above V(UVLO), NFAULT returns to Hi-Z (given no other fault conditions present) and the LDO will be enabled immediately. The CQ output is turned on after T(UVLO) delay.