One of our VSD students @Akshay Kulkarni did some very interesting research work on noise analysis for SKY130 based PLL which was developed in-house by another VSD student @Tim Edwards @Matt Venn @Tim 'mithro' Ansell @mkk @jeffdi @Nickson Jose @Praharsha @Lakshmi - you might want to take a look at below report https://github.com/kulkarniakshay02/avsdpll_noise_analysis