SLUSD37E October 2017 – November 2019 UCC28056
The VOSNS pin monitors output capacitor voltage via an external resistor divider comprising ROS1 and ROS2. An internal comparator (Ovp1) monitors the VOSNS pin voltage (VOS). If the voltage on this pin rises above VOvp1Rise, indicating excessive output capacitor voltage, then the controller transitions to its BstOffb state. In this state switching halts to prevent further increase in the output capacitor voltage. The controller returns to the Runb state, and resumes switching operation, only after VOS falls below VOvp1Fall, indicating that the output voltage has returned to normal range. To limit audible noise, the on-time pulse duration ramps during the transition between Runb and BstOffb states. This ramp method is identical to that for Burst Mode operation.