A 3.3-GHz Integer N-Type-II Sub-Sampling PLL Using a BFSK-Suppressed Push–Pull SS-PD and a Fast-Locking FLL Achieving −82.2-dBc REF Spur and −255-dB FOM

This brief describes an integer-N-type-II sub-sampling phase-locked loop (SS-PLL) incorporating a push–pull sub-sampling phase detector to significantly suppress the spur-induced binary frequency shift keying modulation (BFSK) effect and a low-power fast-locking frequency-locked loop (FLL) to shorten the settling time. Prototyped in 65-nm CMOS, the SS-PLL at 3.3 GHz shows a reference spur of −82.2 dBc, an integrated jitter of 64.9 fs
_rms
(1 kHz to 40 MHz), and an in-band phase noise (PN) of −128.4 dBc/Hz at 1-MHz offset. The corresponding jitter power figure of merit (FOM) is −255 dB. The entire SS-PLL consumes 7.5 mW, with only
$90~\mu \text{W}$
associated with the FLL.