Toshihiko Shimizu

A 1.8 mm 2 , 11 mA, 23.2 dB-NF, discrete-time filter for GSM/WCDMA/WLAN using retiming technique

A discrete-time filter for GSM/WCDMA/WLAN with area reduction technique is presented. The discrete-time filtering is suitable for pass band selection and anti-alias filtering. Reduction of large switched-capacitor area is a key issue for the filter. In this paper, we propose the retiming technique and the optimization of unit capacitor to reduce the number of capacitors. The area of the filter with IQ channels is 1.8 mm2 . Noise Figure (NF) and current consumption in GSM mode are 23.2 dB and 11 mA, respectively. This filter is fabricated in 0.13 um CMOS.

A New Control Method for Switched Buck-Boost DC-DC Converters with Delta-Sigma Modulation for Mobile Equipment

This paper presents a new approach to creating high-performance DC-DC converter systems for mobile-phone applications. The required supply voltage is 2.5 V, and the output voltage of recent lithium-ion secondary-batteries ranges from 4.2 V to about 2 V as they discharge. We have developed a bridge-configuration switching regulator that toggles between voltage-buck and voltage-boost modes, and maintains output voltage regulation even with a small input-output voltage differential. It uses delta-sigma modulation, switches smoothly between voltage-buck and voltage-boost modes with plusmn6 mV ripple (at constant load), and load regulation is within plusmn20 mV for a load current step of 0.5 A