The TPS62065-Q1 pulling the MODE pin low enables power save mode. For the TPS62067-Q1, 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 1% (typical) 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 when the inductor current in the low-side MOSFET switch becomes zero, which indicates discontinuous conduction mode.

During 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 turns on and the inductor current ramps up. After the on-time expires, the switch is turned off and the low-side MOSFET switch is turned on until the inductor current becomes zero. In case the output voltage is still below the PFM comparator threshold, further PFM current pulses are generated until the PFM comparator reaches its threshold. The converter starts switching again after the output voltage drops below the PFM comparator threshold due to the load current.

If power save mode is enabled (TPS62065-Q1, MODE = Low), the device regularly checks to see if PFM mode must be entered. The checking occurs at about a 100-kHz rate and can show up as a small ripple on the output. Enabled forced PWM mode (MODE = High) disables the checking circuit. The TPS62067-Q1 always checks for PFM mode.