ZHCSI58C October 2009 – May 2018 TPS65720 , TPS65721
PRODUCTION DATA.
The TPS6572x step-down converter operates with typically 2.25-MHz fixed-frequency pulse width modulation (PWM) at moderate to heavy load currents. At light load currents the converter can automatically enter Power Save Mode and operates then in PFM mode.
During PWM operation, the converter use a unique fast response voltage mode control 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 through 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 will also turn 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 will ramp down. The current flows now from the inductor to the output capacitor and to the load. It returns back to the inductor through the low-side MOSFET rectifier.
The next cycle will be initiated by the clock signal again turning off the low-side MOSFET rectifier and turning on the on the high-side MOSFET switch.
The DCDC1 converters output voltage is externally adjustable using a resistor-divider at FB_DCDC1.