Low-power Relaxation Oscillator Design

At present,due to the high precision of the crystal oscillator circuit,in the synchronous communication,most of low-power devices generally use crystal oscillator circuit as a clock source,but for some ultra-low power devices such as wireless sensors,as a sleep clock and wake-up clock will lead to the entire circuit system power consumption is still relatively high.In the case of clock accuracy,the use of low-power relaxation oscillator with output frequency of Hz as the sleep clock of low power consumption system can effectively reduce the power consumption of the whole circuit system in sleep mode.Therefore,a low-power relaxation oscillation circuit was designed as a sleep clock applied to low-power RTC chip.The circuit structure of this thesis was improved based on the traditional relaxation oscillator structure and its core sub-circuit was optimized accordingly.For the chip operating temperature range is-40?85?,in order to improve the accruracy of the output frequency,low-power relaxation oscillator for the temperature drift was optimized.Because the relaxation oscillator had a low operating frequency,the focus of temperature drift optimization is mainly on the reference voltage source and the reference current source.For this reason,the reference voltage source and the reference current source were based on 2T(2-Transistor)structure improved circuit.In addition,the low-power comparator circuit was design and optimized,in order to increase its DC gain for improving the accuracy.It was based on a two-stage cascade differential amplifier circuit,and each differential circuit was added to the cross pair.Based on the TSMCO.18?m process,the design and simulation of the low power relaxation oscillator were completed.The simulation results were got:the output frequency was 125.4Hz,the power consumption was 13.2nW,the operating temperature range was-40?85?,temperature drift coefficient was 133.97ppm/?,the area was 0.11mm2.The post-simulation results showed that the designed low power relaxation oscillation circuit satisfied the design indexes and completed the expected design goal.