This paper explores the benefits and costs of integrating an on-chip DC-DC converter as voltage regulator module for reliable power delivery networks (PDNs). We perform detailed time-domain and frequency analyses on PDNs to assess the impact of on-chip DC-DC converter on PDN impedance and overall supply noise behavior. As results show, the reliability of PDNs depends on the DC-DC converter design and its efficiency. Various switching scenarios are analyzed for multiple voltage distributions on circuits of different sizes to explore the benefits of on-chip DC-DC conversion.