This paper presents the design of an LDO-assisted DC-DC voltage regulator in Cadence Virtuoso® based on a 350-nm CMOS technology. This kind of voltage regulator consists of a switching converter together with a classic or LDO (low dropout) linear voltage regulator. While the linear regulator provides the constant output voltage, the switching converter conducts nearly all the current provided to the output load, and keeping the regulator current close to zero where the higher efficiency is achieved. In addition, this paper shows the modeling in Matlab/Simulink. Notice that, this modeling is mandatory in order to predict and assure the stability of the circuit. In addition, it will help to improve the transient response and performance of the circuit.