Abstract

Abstract — This paper describes a dual-mode digitallycontrolled buck converter IC for cellular phone applications. An architecture employing internal power management is introduced to ensure voltage compatibility between a singlecell lithium-ion battery voltage and a low voltage integrated circuit technology. Special purpose analog and digital interface elements are developed. These include a ring-oscillator based ADC (ring-ADC), which is nearly entirely synthesizable, robust against switching noise, and has flexible resolution control, and a very low power ring oscillator-multiplexer based Digital PWM generation module (ring-MUX DPWM). The chip, which includes an output power stage rated for 400 mA, occupies 2mm 2 active area in 0.25-µm CMOS. Very high efficiencies are achieved over a load range of 0.1 to 400 mA. Measured quiescent current in PFM mode is 4 µA. I.

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