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Main Control Loop The LTC3408 usesa constantfrequency, current mode step- down architecture. The main (P-channel MOSFET), syn- chronous (N-channel MOSFET) and bypass (P-channel MOSFET) switches are inte rnal. During normal operation, the internal main switch is turned on each cycle when the oscillator sets the RS latch, and turned off when the cur- rent comparator, ICOMP, resets the RS latch. The peak in- ductor current at which ICOMP resets the RS latch, is con- trolled by the output of error amplifier EA. When the load current increases, it causes a slight decrease in the feed- back voltage, FB, relative to the exte rnal reference, which in turn, causesthe EA amplifier's output voltage to increase untilthe ave rageinductorcurrent matchesthe newload cur- rent. While the main switch is off, the synchronous switch is turned on until the beginning of the next clock cycle.