The Design Of Ultra Low Power Real Time Clock Crystal Oscillator

Ultra-low power chip systems(such as wireless sensor nodes)are widely used in biomedical,environmental monitoring and other fields.However,due to the limited battery storage capacity,power consumption has become a key factor in system design.In order to conserve energy,the wireless sensor network node usually has a short activity,followed by a long idle mode.Reducing the idle mode power consumption can effectively improve the system's standby time,and the clock source is usually the only functional circuit in the idle mode for "wake-up" and the synchronization system.Among the oscillators that are used as clock sources,the quartz crystal oscillator is widely used for its extremely high frequency stability,and low power consumption is the primary starting point for design.In this thesis,an ultra-low power crystal oscillator using multi-voltage domain and pulse-driven method was designed.Firstly,the inverting amplifier in the conventional crystal oscillator circuit is decomposed into a preamplifier stage and a driver stage.The preamplifier stage output in the high voltage domain avoids the driver-level circuit operating in the subthreshold region and ensures the low on-resistance required for stable oscillation of the circuit,while the driver-stage circuit operates in the low voltage domain so that the amplitude of the crystal is very low,then the energy required to compensate for the steady oscillation of each cycle of the crystal is also reduced.Then,in order to further reduce the power consumption,the preamplifier stage is constituted by a pulse generating circuit based on the Schmitt trigger,uses the delay stability of the Schmitt trigger to determine the position of the pulse and uses the inverter delay chain to determine the pulse width,the final pulse signal from the bootstrap circuit boost output to the drive circuit.Finally,in order to improve the efficiency of the power supply,the different power required in the circuit is generated by the switched capacitor networkBased on the TSMC 0.18?m CMOS process,the design of the ultra-low power crystal oscillator circuit is completed.The layout area is 0.08mm2.The simulation results show that the operating temperature range is-20?-80?.In the TT process corner,0.6V power supply voltage and room temperature,the minimum power consumption of the circuit is 11.44nW.The operating voltage range is 0.6V-0.74V and power supply sensitivity is 71.4 ppm/V.