A buck converter circuit provides the output voltage responsive to the boosted input voltage from the capacitor pump circuit in the first mode of operation and provides the output voltage responsive to the input voltage in {HEAD ~ a second mode} of {TAIL ~ operation} when the input voltage is above the desired voltage level 
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A buck converter circuit provides the output voltage responsive to the boosted input voltage from the capacitor pump circuit in the first mode of operation and provides the output voltage responsive to the input voltage in { HEAD ~ a second mode } of { TAIL ~ operation } when the input voltage is above the desired voltage level
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