High efficiency on-chip charge pump DC–DC converter for LCD drivers

An on-chip charge pump (CP) DC–DC converter applicable to potable displays is described. A merged 2×/3× booster eligible for both single-phase pumping and dual-phase pumping is developed. A closed-loop sensing scheme with analog/digital mixed-mode voltage regulation helps to ensure a low ripple output voltage and high power transfer efficiency. A test vehicle was implemented for a DC input range of 2.2–3.6 V and the DC output of 5 V with a load condition of 20 mA in a standard 0.35-μm 2poly-4metal CMOS process. The test results reveal output ripple of less than 80 mV and efficiency of 77.4% in the 2× dual phase mode.