A Multi-phase Clock Generating Circuit Applied To High Precision TDC

With the continuous growth of the automotive industry,the speed of research of driverless technologies that assist people in making emergency decisions is also accelerating.Lidar ranging systems have become an indispensable part of it.Time-to-digital converters(TDC)module in ranging systemscal obtains the detection distance by calculating the time difference between the laser pulse emission and the return signal.The accurate clock pulse signal can provide a higher resolution for the TDC module to achieve finer long-range detection,and the layout of multi-phase clocks and jitter deviation and power consumption will have a crucial impact on multi-channel high-accuracy TDC.Based on the analysis and summary of the clock circuits applied to TDC at home and abroad,combined with the laser ranging requirements of this project,the4-channel high-precision TDC module is used to achieve the longest distance of 350 meters and the measurement accuracy of the centimeter level.Based on the SMIC0.11μm process,a new PLL cascade ILRO structure is designed,and a 4-channel multi-phase clock is designed.The main contents of this article include:1.Briefly introduces the development of lidar ranging system and multi-phase clock circuit at home and abroad,and proposes a new structure in combination with this project;2.Analyze the basic theory of the phase-locked loop,linear analysis of each module to obtain the linear transmission function of the phase-locked loop circuit,study the noise model of the third-order charge pump phase-locked loop,analyze the transmission characteristics of each noise source,and design this paper.The parameters of the phase-locked loop are verified by MATLAB program for stability,and modeling and simulation are performed in Simulink to analyze the lock time and so on.3.Expand the multi-phase clock circuit and analyze the structure of each module,design circuit modules to effectively avoid or eliminate the non-ideal factors,and design a delay-based circuit with a wide range of adjustments.The unit type current starvation ring oscillator analyzes the principle of injection locking.It uses the injection locked oscillator(ILRO)of a shared oscillator delay unit,based on a600 MHz phase-locked loop PLL circuit,locking 4 ILROs to the PLL clock to output four-way 16-phase clock signal,combined with TDC module for simulation,to meet design requirements.4.Complete the layout and post-simulation analysis of the design circuit,and compare the differences before and after the simulation,so that the post-simulation meets the design requirements.The multi-phase clock signal designed in this paper realizes the output of 4channels of 16-phase signals with a time interval of 104 ps,so that each TDC module can enjoy a single channel of multi-phase clock signal,and ILRO uses the oscillator delay unit in the common PLL and replicates the bias current.The method reduces the effect of PVT.The VCO phase noise is-102 dBc / Hz at 1MHz frequency offset,the lock time of the phase-locked loop is less than 1μs,the power consumption of the phase-locked loop is 6m A@1.2V,and the output of the overall multi-phase clock circuit is adjacent to the clock The maximum deviation of the interval is less than 1%,and the total power consumption is about 42mA@1.2V.The innovations in this article include:1.ILRO uses an 8-stage ring vibration structure in a common phase-locked loop to achieve 16-phase output,and the time interval reaches 104 ps,which enables measurement accuracy to achieve centimeter level.2.The injection signal of the PLL is injected into the four ILRO modules through the principle of injection locking,and four channels of 16-phase clock output signals are realized,so that each channel of the 4-channel TDC module can only enjoy one clock signal,and the overall clock is meeting the design requirements.To achieve lower power consumption.