一种基于CMOS工艺的高精度片内振荡器的设计

Design of a on-chip CMOS Oscillator with High Precision

采用恒流源充放电及温度补偿技术设计了一款结构简单、易于集成的片内振荡器。该模块的核心为利用带隙基准电流源产生一路零温度系数电流,并用该电流源对电容进行充放电;设置比较器的高低阈值电压的差值为负温度系数与电容的正温度系数相互补偿,尽可能减弱温度对振荡周期的影响,产生高稳定且占空比可调的矩形波。采用华虹NEC0.35μmCZ6H工艺设计,经CadenceSpectre软件仿真表明标准状况下该模块振荡频率为6.321MHz,在-20到100℃的温度区间内其温度系数仅为42ppm/℃。

A kind of on-chip oscillator with simple structure and is easy to integrate was designed usingconstant current source charge-discharge and temperature compensation technologies .The key element of the circuit is a temperature independent bandgap current source generated from the superposition of PTA-T and NTAT currents .A capacitance was charged and discharged accurately by the current source whil-e the difference between the High threshold and Low threshold of comparator was designed to be NTA-T to compensate the PTAT of capacitance in order to weaken the impact of temperature to the period of oscillation, generating precious rectangle wave oscillation with duty ratio adjustable. This design is i-mplemented in HHNEC 0.35 μm process. Spectre simulation shows up that in standard situation this mod-ule offers A 6.321MHz clock signal, and it＇ s temperature coefficient is only 42ppm/℃ from-20℃ to 100℃.