Design of a Transient Voltage Clamp (TVC) Based On Output Impedance Analysis

This paper presents a new design of methodology of the transient voltage clamp (TVC) based on the output impedance. TVC works in parallel with a voltage regulator (VR)´s ceramic cap to achieve a faster voltage regulation without huge bulk capacitor. Hence it acts as a replacement of the bulk cap. Due to the limited control bandwidth, traditional VR could not respond rapidly to the load transient. As a result, a large output voltage spike can occur during load transient hence requiring large amount of bulk cap to decouple the VR from the load. The specific function of TVC is to replace the bulk cap and sink or source large currents similar to the bulk cap. This will allow fast transient response without large bulk capacitor. The main challenge in applying the TVC is how to design the TVC that will not interfere with VR operation. In this paper, the total system output impedance, the TVC impedance concept, system control bandwidth and transient response are discussed. The theoretical analysis will be confirmed by the cadence simulation results.