A 0.07-ppm/step differential digitally controlled crystal oscillator with guaranteed monotonicity

This paper presents a differential digitally controlled crystal oscillator with differential 26MHz sine wave outputs. The DCXO achieves a phase noise of -138dBc/Hz at 1 kHz offset and -152dBc/Hz at 10 kHz offset. And it has a ±32 ppm fine tuning range with 0.07ppm tuning step, which satisfy the GSM, WLAN and WCDMA specification. The circuit is implemented by differential architecture with a cheap off-chip crystal. The overall power consumption is 3.7 mA with 1.6 V power supply.