Design Of Low Power CMOS Temperature Sensor For Temperature Compensated Crystal Oscillators

Battery-powered low-power wireless sensor nodes are periodically woken up to enter the working state to transmit data.Most of the time they are in the sleep state and only maintain clock timing.A high-precision,low-power clock system is required to avoid wasted dynamic energy consumption when the node is awaked with a long synchronization time and save dormancy energy consumption.Temperature compensation is a common method to achieve a high-precision clock,but its power consumption is much greater than the clock circuit.As a result,low-power temperature sensor is the key to achieve low-power clock system.A low-power CMOS temperature sensor is designed by using sub-threshold MOSFETs to design low-power temperature sensing elements and two-stage operational amplifiers and replacing traditional analog-to-digital converters with frequency-to-digital converters together with custom circuit technology.The main work is as follows:1)A low-power temperature sensing element is designed based on the 2T voltage reference structure by using sub-threshold circuit design technique.2)A sub-threshold two-stage operational amplifier is designed based on the basic two-stage operational amplifier by adjusting transistors' operating regions.3)The current mirror is replaced with voltage-to-current converters with a stack structure to avoid a dual current path and save half of the current consumption of the current generation circuit.4)Frequency-to-digital converters are composed of oscillators and asynchronous counters.A ring oscillator with a new structure is designed by the use of transmission gates and inverters in cascade form,reducing the oscillator series.Besides,custom circuit technology is used to design inverters and triggers.And asynchronous counters are designed with fully custom triggers and the control logic and timing of the counters are optimized.The temperature sensor is designed based on the TSMC 0.18?m CMOS process.The sensor operates at 1.2V and occupies 0.078mm2.Simulation results show that the temperature sensor consumes 84nW at 25?of TT corner.With a conversion time of 17ms,0.14?/LSB resolution is achieved.The temperature sensor consume,s 1.428nJ per conversion.After 4-point calibration,an inaccuracy of-1.88?/+1.86? is achieved across-40? to 85?.