Research And Design Of Phase Locked Loop Based On DTOF

Direct Time of Flight(DTOF)has become a popular future development direction of 3D depth vision technology due to its long distance measuring and good low-light performance.As a key component of the DTOF image sensor,the phase-locked loop,the performance of the phase-locked loop also determines the ranging accuracy and error of the DTOF image sensor.Based on the working principle of DTOF image sensor ranging,combined with the advantages and disadvantages of different phase-locked loop design structures,this paper determines the basic parameters of the phase-locked loop,and designs a phase-locked loop circuit that meets the ranging requirements of DTOF image sensors.A low dropout linear regulator(LDO)circuit design is designed.This paper starts from the basic method of designing the circuit,and firstly learns the basic principle of the circuit.The charge pump phase-locked loop includes a voltage-controlled oscillator,a frequency discriminator,a charge pump,a loop filter and a frequency divider.Then,the transfer function of the phase-locked loop is deduced from the principle,and the stability condition is obtained.And according to the most concerned phase noise of the phase-locked loop,according to the Mersen’s law,the noise transfer function of each module is calculated and obtained.Understand how to design to reduce noise in phase-locked loops.And use verilog-A language to verify phase-locked loop parameters before circuit design.Master the theoretical knowledge of the system,and finally complete the phase-locked loop circuit design.The voltage-controlled oscillator adopts a pseudo differential pair inverter design to achieve a wide dynamic range,and the power supply noise is suppressed by LDO.The charge pump adopts the current steering charge pump,which effectively improves the working speed of the charge pump,and adopts a method to suppress the parasitic effect of the switch tube of the charge pump,which effectively improves the consistency of the upper and lower current sources.Finally,layout design and simulation are completed.Completed DTOF LDO power circuit design,pre-simulation design and layout design.Stability problems occur in post-simulation,and this paper solves the post-simulation stability problem by star connection.After the post-simulation,the phase-locked loop designed in this paper is under the TOWER 180nm process,the input frequency is 25MHz,the typical output frequency is2GHz,and the output frequency range of the oscillator is 2.6GHz to 1.6GHz.The loop lock time is 6us.The effective value of the Period jitter is 4.6ps,and the effective value of the rms JC jitter is 5.58ps in the 10Hz to 1GHz integration.The rms JCC jitter is 5.86ps rms over 10Hz to 1GHz integration.Peak-to-peak JCC jitter effective value is 32ps.The total layout area of its phase-locked loop and LDO is 0.02mm~2.The phase noise of the VCO is92d Bc/Hz@1MHz.The maximum output current of the LDO is 80m A,the load regulation rate is 1.9%,and the linear modulation rate is 4.36%.The phase-locked loop designed in this paper is suitable for DTOF image sensor,which can meet the distance measuring requirement of 5M,and the ranging error is controlled within 2cm.The phase-locked loop has the advantages of simple structure,small area,high oscillation frequency,and small output jitter,which meets the requirements of DTOF ranging.And the LDO designed in this paper is used to supply power for the phase-locked loop and the charge pump alone,which can effectively suppress the noise from the power supply.The voltage-controlled oscillator of the phase-locked loop has a simple structure and a small layout area,and can form an array with a time-to-digital converter in DTOF applications,thereby fulfilling the DTOF ranging requirement.The array formed by the voltage-controlled oscillator is also powered by the LDO designed in this paper.Further suppress the noise of the power supply.The ranging error is reduced.