TPA3223 has fast reacting current sensors on all high-side and low-side FETs. To prevent output current from increasing beyond the overcurrent threshold, TPA3223 uses current limiting of the output current for each switching cycle (Cycle By Cycle Current Control, CB3C) in case of excess output current. CB3C prevents premature shutdown due to high output current transients caused by high level music transients and a drop of the real load impedance of the speaker, and allows the output current to be limited to a maximum programmed level. If the maximum output current persists, for example the power stage being overloaded with too low load impedance, then the device will shut down the affected output channel and the affected output is put in a high-impedance (Hi-Z) state until a RESET cycle is initiated. CB3C works individually for each full-bridge output. If an over current event is triggered, then the CB3C performs a state flip of the full-bridged output that is cleared upon beginning of next PWM frame.

Figure 9-14 CB3C Timing Example