Study On A Clock Generating Circuit With High Precision Based On The Temperature And Process Compensation

As an indispensable part in the vast majority of the circuit,clock circuit has been playing an important role in different kinds of circuits since it emerged.With the development of the progress of integrated circuit manufacturing technology and the expansion of it's application scope,the stability of the output signal of clock circuit more and more receives takes.This paper designes a clock circuit of the high stability applied in the mixed-signal circuit,the output signal of the clock circuit is nearly independent of process deviation,temperature change and power supply fluctuation.In this paper the working principle of the clock circuit is carefully analyzed,and the influence of temperature variation and process deviation on the circuit performance are also detaily researched.This paper finally adopts the method of digital calibration to implement the circuit after comparing the several kinds of method to realize the high stability of clock circuit.In this paper,the clock circuit mainly includes two parts:the clock generating circuit and clock calibration circuit.The clock generating circuit includes:reference circuit,low dropout linear regulators and ring oscillator.Clock calibration circuit consists of digital control circuit,current mirror array and reset circuit.Bandgap and low dropout linear regulators provide charge and discharge current and power supply volta ge for ring oscillator,the current and voltage are independent of temperature.Through the analysis of the temperature characteristic of triode,this paper adopts the way of V_BE linearization compensation to compensate the high order of triode conduction voltage.Finally,the temperature-drift of the reference voltage less than 5ppm/?.In order to restrain the power fluctuation influence on clock frequency,this paper adopts low dropout linear regulators to power a ring oscillator.In order to further improve the stability of the clock signal and reduce the error caused by the process deviation,a new kind of digital calibration algorithm is proposed in this paper,this algorithm has fast convergence speed and high precision.The clock signal feedback to digital control module,the digital control module outputs an 8-bit digital signal through a calibration algorithm,which controls the charge and discharge current of current mirror array to adjust the deviation of the clock signal caused by the process fluctuation and temperature change.This paper adopts SMIC0.18 um MMRF standard CMOS process to design the clock circuit,which is based on the temperature and process compensation.The simulation results show that under the tt,ff,ss,snfp,fnsp process angle and-40?⁸0?temperature range,2 MHZ clock signal can be output,errors are within±2%.The post-layout simulation results are correspond with the circuit simulation.Then taped out the clock circuit through MPW to verify it's correctness.Eventually the results of the test chip show that the output clock signal of the circuit can satisfy the requirements of design at different temperatures and supply voltage range.