Low-dropout (LDO) regulator output impedance analysis and transient performance enhancement circuit

This paper presents a low-dropout regulator with a transient performance enhancement circuit. The transient performance enhancement circuit improves the transient response time by sinking a remaining current in a power delivery path. Due to the limited control bandwidth, traditional LDO could not respond rapidly to the load transients. As a result, a large output voltage spike can be occurred and the output voltage settling time is long during the load transients. In this paper, the stability conditions and the output impedance of LDO are discussed, and the output voltage spike and current distributions in the power delivery path are analyzed. The theoretical analysis will be confirmed by the cadence simulation results.