1MHz multi mode regulated charge pump with improved light load efficiency without sacrificing output ripple

The design of a 1 MHz regulated multi mode charge pump using IBM7RF technology is described in this paper. This charge pump converts 2.7-4.5 V input voltage to a regulated 5 V output. The power stage includes nine PMOS switches and one NMOS acting as a controlled current source with 50% duty cycle. Together with three flying capacitors and the output capacitors, the converter can work in 2×, (3/2)× and (4/3)× modes, which allows high efficiency over a wide input voltage range. To obtain 500 mA maximum output current, the sizes of the PMOS switches and the NMOS device are big. This makes it difficult to obtain good efficiency at light load. An adaptive device size method is proposed to solve this problem.