
Switched-Capacitor DC-DC Converters
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Moreover, in such a PFM-controlled DC-DC converter, for a given load imped-
ance and a fi xed conversion ratio, the duration of the idle mode will be decreased as
the load current increases, because the converter must boost the output voltage to
keep up with the increasing product of the load current and impedance. However,
under the same conditions, the duration of the active mode will be decreased once
the input battery voltage reaches a point when the resulting output voltage is equal to
or higher than the desired voltage (V
desired
). In an intuitive sense, we can say that the
switching frequency, whic