8.1 Overview

The TPS6229x step down converters operate with typically 2.25-MHz fixed frequency pulse width modulation (PWM) mode at moderate to heavy load currents. At light load currents, the converters can automatically enter power save mode and operate then in pulse frequency modulation (PFM) mode.

During PWM operation, the converters use a unique fast response voltage mode controller scheme with input voltage feed-forward to achieve good line and load regulation allowing the use of small ceramic input and output capacitors. At the beginning of each clock cycle initiated by the clock signal, the high side MOSFET switch is turned on. The current flows now from the input capacitor via the high side MOSFET switch through the inductor to the output capacitor and load. During this phase, the current ramps up until the PWM comparator trips and the control logic will turn off the switch. The current limit comparator also turns off the switch in case the current limit of the high side MOSFET switch is exceeded. After a dead time preventing shoot through current, the low side MOSFET rectifier is turned on and the inductor current ramps down. The current flows now from the inductor to the output capacitor and to the load. It returns to the inductor through the low side MOSFET rectifier.

The next cycle is initiated by the clock signal again turning off the low side MOSFET rectifier and turning on the high side MOSFET switch.