As ASIC supply voltages approach one volt, the source-impedance goals for power distribution networks are driven ever lower as well. One approach to achieving these goals is to add decoupling capacitors of various values until the desired impedance profile is obtained. An unintended consequence of this approach can be reduced power supply stability and even oscillation. In this paper, we present a case study of a system design which encountered these problems and we describe how these problems were resolved. Time-domain and frequency-domain analysis techniques are discussed and measured data is presented.