A Ramp Integrating Capacitor Current Constant On-time (RICCCOT) Controlled Buck Converter with High Noise Immunity in DCM

This paper proposes a ramp integrating capacitor current mode constant on-time (RICCCOT) controlled buck converter. A capacitor current-controlled modulation scheme ensures an ultra-fast load transient response. However, this scheme suffers from sensing circuit mismatch-induced instability, hence an integrated ramp is proposed to mitigate the problem. Moreover, the proposed integrated ramp improves noise immunity and provides accurate trigger in discontinuous-conduction mode (DCM). Implemented in a 28nm CMOS process with a 5-MHz high switching frequency, this circuit occupies a total area of 605 μm by 431 μm in width and length. Finally, the chip simulation results show a fast load transient response, which is 48mV voltage drop and 1μs response time under the conditions of 1.1V output voltage and 0.9A load step-up with 0.9A/1ns slew rate.