一种低功耗CMOS晶振电路设计

A Design of Low Power CMOS Crystal Oscillator Circuit

在组成反相器的两个晶体管的栅端添加一个串联电容,直流通过连接在反相器内部的大电阻偏置这两个晶体管,P管被低于电源电压一个阈值的电压偏置,N管被高于低电压一个阈值的电压偏置,偏置电压通过电流镜镜像,因此受温度和工艺的影响较低。一种低功耗CMOS晶体振荡电路利用上述反相器,它的开启电压低于P管和N管的阈值之和,整体电路消耗的电流大概为传统电路的1/5。此晶振电路基于MXIC 0.5μm仿真模型验证实现,整体电路消耗的功耗电流小于750 nA。

A CMOS inverter of two-transistors has two transistor gates coupled together by a coupling capacitor. DC gate bias is supplied to each transistor through high value resistors. The P-channel transistor is biased to a threshold below the power and the N-channel transistor is biased to a threshold above ground. The biasing voltage are developed through the use of a current mirror so that the biasing is independent of processing variables and temperature. A crystal oscillator created using such an inverter and biasing will operate at voltage substantially below sum of P and N thresholds and at a current level about one-fifth of that of a conventional CMOS oscillator. This low power CMOS crystal oscillator circuit was designed based on MXIC＇s 0.5 μm CMOS process,the current consumption of the whole circuit is under 750 nA.