Design of new capacitor-switch array usable on DTCXOs

Abstract

A new capacitor array scheme, called TACA (temperature adaptive capacitor array) is proposed. It guarantees monotonicity and saves the silicon area at the same time. We also have developed TCXO, which can be used over wide range of frequency. The oscillator and the capacitor array were fabricated with a 0.5 mm CMOS process. Complete digital trimming of the DTCXO with 0.2 ppm trimming accuracy was achieved. Design consideration for the crystal oscillator is presented. The accurate analysis of the oscillation amplitude is described and compared with the simulation, the measurement and the previous model.