A four-phase integrated buck converter in 45 nm silicon-on-insulator (SOI) technology is presented. The controller uses unlatched pulse-width modulation (PWM) with nonlinear gain to provide both stable small-signal dynamics and fast response (700 ps) to large input and output transients. This fast control approach reduces the required output capacitance by 5 in comparison to a conventional, latched PWM controller at a similar operating point. The converter switches package-integrated air-core inductors at 80 MHz and delivers 1 A/mm at 83% efficiency and 0.66 conversion ratio. A network-on-chip (NoC) serves as a realistic digital load along with a programmable current source capable of generating load current steps with slew rate of 1 A/100 ps for characterization of the control scheme.