This slide illustrates how the closed loop feedback is implemented in a switching converter. The error amplifier is the heart of the feedback loop. The non-inverting input is connected to the internal voltage reference, while the inverting input is connected to the feedback resistor divider. The error amplifier, like any operational amplifier, needs compensation to be stable and work properly. This compensation circuitry can be internal (predefined components are integrated in the regulator) or external. External compensation allows more flexibility in the transient response and in managing heavy capacitive loads, with the drawback that external components must be used and chosen properly to stabilize the loop, ST’s simulation tools are very helpful in that regard. This error signal and a sawtooth waveform are fed to a comparator, when the comparator trips, the PWM control turns the HS switch off. The next cycle is initiated by the clock signal turning off the LS, and turning on the HS. During each cycle, the PWM comparator modulates the power transferred to the load, based on the feedback error voltage. The families of switching converters listed on this slide use a voltage mode feedback control with external compensation.