The TPS54561 is designed to operate with input voltages above 4.5 V. When the VIN voltage is above the 4.3 V typical rising UVLO threshold and the EN voltage is above the 1.2 V typical threshold the device is active. If the VIN voltage falls below the typical 4-V UVLO turn off threshold the device stops switching. If the EN voltage falls below the 1.2-V threshold the device stops switching and enters a shutdown mode with low supply current of 2 µA typical.

The TPS54561 will operate in CCM when the output current is enough to keep the inductor current above 0 A at the end of each switching period. As a non-synchronous converter it will enter DCM at low output currents when the inductor current falls to 0 A before the end of a switching period. At very low output current the COMP voltage will drop to the pulse skipping threshold and the device operates in a pulse-skipping Eco-mode. In this mode the high-side MOSFET does not switch every switching period. This operating mode reduces power loss while keeping the output voltage regulated. For more information on Eco-mode see Section 7.3.3.