A f(REF)/5 Bandwidth Type-II Charge-Pump Phase-Locked Loop With Dual-Edge Phase Comparison and Sampling Loop Filter

Abstract

The bandwidth (BW) of type-II charge-pump (CP) phase-locked loop (PLL) is extended to f(REF)/5 by dual-edge phase comparison (DEPC) to achieve better phase noise suppression of voltage-controlled oscillator. The reference spur that may result from the unequal duty cycles of reference clock and feedback clock is prevented by sampling loop filter (SLF). A prototype 1.25-GHz type-II CP-PLL employing the proposed DEPC and SLF has been implemented in a 65-nm CMOS technology and achieves 50-MHz BW with 250-MHz reference clock. The phase noise is smaller than -121 dBc/Hz at 1-MHz offset from the carrier, and the reference spur is smaller than -58.5 dBc. The type-II CP-PLL consumes 14.9 mW from a 1.2-V supply and occupies 0.107-mm(2) silicon area.