Area efficient low power crystal oscillator with automatic amplitude control

A CMOS Crystal Oscillator with automatic amplitude control (AAC) is presented which occupies low area and consumes lower current when compared to existing state of the art designs. Amplitude control loop based implementations of low frequency crystal oscillators usually achieve low-power operation at the expense of die area. The proposed design aims at reducing the overall area by replacing the bulky RC loop filter with a switched capacitor filter operating on the clock generated by the oscillator itself. The circuit is reduced to its basic form after removing redundant branches and devices consuming high voltage headroom, thereby minimizing power dissipation and maximizing operational supply range. The implementation and comparisons are done for 32 kHz in TSMC 65nm CMOS process. The crystal oscillator core consumes 82nA, occupies 12500μm2 and works reliably over PVT variations.