One chip-low power digital-TCXO with sub-ppm accuracy

The digital TCXO (DTCXO) has been studied extensively because of its high frequency accuracy and rapid start-up time. The value of compensation capacitance used in the DTCXO is stored in ROM or calculated by computing circuit. In this work, ROM and computing circuit are integrated together to obtain the merit of both schemes; accurate value and high resolution of compensation capacitance, respectively. The DTCXO contains a temperature sensor, A/D converter, controller, EEPROM, capacitor bank, and oscillator. The oscillation frequency can be pulled from /spl plusmn/25 ppm to the required frequency with sub-ppm accuracy. The maximum power consumption of the total chip is 6.6 mW at 3.3 V. The chip, die size of 9mm/sup 2/, is fabricated by a 0.5 /spl mu/m CMOS technology.