Design and Implementation of a Clock Generator Based on All Digital PLL (ADPLL)
Authors: Awasthi Shashank , Yadav Satya Prakash , Chhabra Manish , Gupta Richa , Pokhariyal Rajesh 
Published: October 2024

Every electronic circuit now includes a clock, which is essential because it
regulates the speed and efficiency of electronic circuits. The need for reliable and
accurate clock generation mechanisms in the circuits thus increases. There are two
ways to generate a clock. The first option is to use a crystal oscillator, which gives the
circuit a fixed clock. However, if different clocks are required in separate system
components, we must use several crystal oscillators, which increases the circuit's size
and complexity. The second choice is to employ a phase-locked loop (PLL) clock
generator system, which allows us to produce precise and wide-ranging clocks for the
various components of the system or circuit by utilizing dividers and multipliers.
Digital methods are used in the design and implementation of a clock generator based
on an All-Digital Phase-Locked Loop (ADPLL) to provide reliable and precise clock
signals. ADPLLs are appealing substitutes for conventional analog PLLs because they
have better noise immunity, are scalable, and are simple to integrate into digital
systems. In this project, a method for all digital phase-locked loops (ADPLL) that
solely makes use of digital cell libraries is demonstrated. For use in digital circuits, this
ADPLL is intended to create a broad frequency range. The suggested ADPLL is
portable for different processes and ideal for SoC applications since it can be
implemented using standard cells. It will be created using MATLAB Simulink
modeling, and then it will be put into use on an XILINX FPGA. An ADPLL clock
generator's design and implementation process generally includes the following steps: The appropriate clock frequency range, stability criteria, phase noise specifications,
power consumption restrictions, and other performance factors should all be
determined. Architecture Selection: Based on the system requirements and trade-offs,
select a suitable ADPLL architecture. The advantages and disadvantages of various
designs, such as Bang-Bang, Sigma-Delta, and Delay-Locked Loop (DLL), vary.
Designing the ADPLL's separate parts, such as the PFD, DLF, NCO, and frequency
divider, is known as component design. Designing digital circuitry and algorithms to
carry out the necessary operations is required. Simulation and Verification: To verify
the ADPLL design's performance, functionality, and stability, specialized software
tools are used. If required, we change the design parameters. Layout and Physical
Design: Create a hardware description language (HDL) implementation of the ADPLL
design and layout and design the circuitry physically. This takes into account factors
like power distribution, noise reduction, and signal integrity. Integration and testing:
The ADPLL design should be integrated into the larger system, connected to the
reference clock source, and tested thoroughly to ensure that it operates as expected
under a variety of circumstances. The ADPLL design should be tweaked to improve
performance, such as by lowering power consumption, jitter performance, or lock time.