The input power supply to the TPS8268x must have a current rating according to the input voltage and output current of the TPS8268x. TPS8268x provides a fast transient response due to its high switching frequency and fast control loop. For highly dynamic loads, the device demands high inputs currents within a short time. The power supply to TPS8268x therefore needs to have a low output impedance in order to keep the input voltage stable during fast load changes. Make sure the input voltage to TPS8268x at any time is above the minimum voltage level required to supply the load at the output. See the electrical characteristics for the minimum input voltage for a given load current for the different output voltage versions. Additional input capacitance needs to be added if the input voltage dops below the minimum level required.