FPGA VALIDATION OF EVENT-DRIVEN ADPLL

1SCHOOL OF ELECTRICAL AND ELECTRONIC ENGINEERING, UNIVERSITY COLLEGE DUBLIN, IRELAND

2LIP6, SORBONNE UNIVERSITY PARIS, FRANCE

Eugene Koskin1, Pierre Bisioux1, Dimitri Galayko2, and Elena Blokhina1

Outline:

• Motivation

• The model of an event-driven PLL

• Structural blocks of the PLL

• Noise modeling

• Transient response

• Phase portraits

• Conclusions

Motivation:

• Need for synchronisation in several fields of science and engineering, including power networks, IoT,

semiconductor laser arrays, brain networks, chemical oscillations and others.

• Clock generators in microprocessor engineering.

Schematic diagram

Block diagram of an ADPLL that includes the digital time detector, the loop filter,the frequency divider, the reference clock and DCO.

Digital Time Detector

Block diagram of the implemented DTD and the schematic of the 10-bit TDC.

Digitally Controlled Oscillator

Block diagram of the inverter ring used as the DCO, with a 6-bit input DCOin and 5-bit output LOC.

Noise measurements

DCO’s properties: (a) Dependence of period standard deviation on its average; (b) PDF for normalised periods.

Measured step response of the ADPLL on the reference signal for several value of PIC parameters.

Phase Portraits

Phase Portraits

Phase Portraits

Conclusions:

We studied dynamical properties of an event-driven ADPLL through FPGA modelling and compared the results with the theoretical model developed in recent works.

• We showed that the FPGA model stays in a very good agreements with theoretical predictions. This was supported by comparison of the ADPLL behaviour in the frequency acquisition and stationary regimes.

• We demonstrated that ADPLL is out of control when the ratio Ki/Kp > 0.5. Below that value, ADPLL locks to the reference signal having jitter depending on the control parameters.

• The measurements of the slope in the transient regime showed that the frequency acquisition rate depends mostly on Ki and does not depend on Kp. Such a frequency acquisition rate can be used as a constraint for an optimisation problem aimed to minimise the timing error.