At TPS62065 pulling the MODE pin low enables power save mode. In TPS62067 power save mode is enabled per default. If the load current decreases, the converter enters power save mode operation automatically. During power save mode the converter skips switching and operates with reduced frequency in PFM mode with a minimum quiescent current to maintain high efficiency. The converter positions the output voltage typically +1% above the nominal output voltage. This voltage positioning feature minimizes voltage drops caused by a sudden load step.

The transition from PWM mode to PFM mode occurs once the inductor current in the low-side MOSFET switch becomes zero, which indicates discontinuous conduction mode.

During the power save mode the output voltage is monitored with a PFM comparator. As the output voltage falls below the PFM comparator threshold of V_OUTnominal +1%, the device starts a PFM current pulse. For this the high-side MOSFET switch will turn on and the inductor current ramps up. After the on-time expires the switch will be turned off and the low-side MOSFET switch will be turned on until the inductor current becomes zero.

The converter effectively delivers a current to the output capacitor and the load. If the load is below the delivered current the output voltage will rise. If the output voltage is equal or higher than the PFM comparator threshold, the device stops switching and enters a sleep mode with typically 18 µA current consumption.

In case the output voltage is still below the PFM comparator threshold, further PFM current pulses will be generated until the PFM comparator threshold is reached. The converter starts switching again once the output voltage drops below the PFM comparator threshold due to the load current.

The PFM mode is exited and PWM mode entered in case the output current can no longer be supported in PFM mode.