AN023

AN023 An Useful Model for Charge Pump Converter Introduction Analysis This application note focuses on the analysis of the charge pump and its equivalent circuit. The AIC1845 is a micro-power charge pump DC/DC converter that produces a regulated 5V output. This kind of converter uses capacitors to store and transfer energy. Since the capacitors can not change their voltage level abruptly, the voltage ratio of VOUT over VIN is limited to some range. Capacitive voltage conversion is obtained by switching a capacitor periodically. It first charges the capacitor by connecting it across a voltage source and then connects it to the output. Referring to Fig.1, During the on state of internal clock, Q1 and Q4 are closed, which charges C1 to VIN level. During the off state, Q3 and Q2 are closed. The output voltage is VIN plus VC1, that is, 2 VIN. VIN CIN ION Q1 Q2 RDS-ON ESR VOU T COUT Q3 C1 Q4 RDS-ON Fig.2 The on State of Charge Pump Circuit VIN CIN RDS-ON Q1 Q2 VOU T ESR COUT Q3 RDS...