Analysis of switch-induced error voltage for automatic conversion mode change charge pumps

This paper presents an exact expression for switch-induced error voltage which would cause a spike voltage on the output capacitor of the automatic conversion mode change (ACMC) charge pumps. The spike voltage will introduce several undesired problems—large output voltage ripple, serious frequency noise and low efficiency. Some methods used for reducing the spike voltage are provided by the proposed expression. An equivalent lumped model is used for deducing the expression. The ACMC charge pump circuit has been designed in SILTERRA 0.18 μm CMOS process. The experiment results show that the value of the spike voltage can match the expression well. Compared with three different improved versions, the spike voltage caused by the switch-induced error voltage can be reduced obviously. (paper)