This innovation presents a new enhanced V2-type constant on-time control architecture with digital implementations for solving the ripple oscillation issues when using small ESR capacitors in a converter. Instead of directly sensing the inductor current, an inductor current ramp estimator with the drift compensation is proposed as adding a virtual ESR ripple to the output voltage. Only the input voltages are required to be sampled for the estimation. And the performance with using the estimated current ramp is better than using an external ramp, which is widely used for solving the instability issue.