A 1.5 GHz phase-locked loop with leakage current suppression in 65 nm CMOS

In the nanoscale CMOS process, the problem of leakage current causes the performance of the analog circuits to degrade. The leakage current of a loop filter, which is realised by MOS capacitors, significantly degrades the jitter performance of a phase-locked loop. A leakage suppression circuit is presented by using a combination of switchable varactors and current sources to compensate the leakage of MOS capacitors in a loop filter. This PLL has been fabricated in a 65 nm CMOS process and the core area is 0.4 x 0.5 mm(2). With the leakage suppression circuit, the peak-to-peak jitter and the rms jitter are 43 and 5.36 ps, respectively. The power is 17 mW for a 1.2 V supply.