Hot carrier effects on CMOS phase-locked loop frequency synthesizers

Abstract

Two CMOS phase-locked loop chips are designed and fabricated in 0.5 µm n-well CMOS process using single-ended voltage-controlled oscillator and differential voltage-controlled oscillator circuits. Hot carrier effects, jitter and phase noise performances are investigated and analyzed. On-chip measured experimental results show that for the phaselocked loop with the single-ended voltage-controlled oscillator working at 500 MHz carrier frequency, phase noise is −76 dBc/Hz at 10 kHz offset frequency and −119 dBc/Hz at 1 MHz offset frequency. For the phase-locked loop with differential voltage-controlled oscillator working at 500 MHz, phase noise reaches −82 dBc/Hz at 1 kHz offset frequency and −122 dBc/Hz at 1 MHz offset frequency. Tuning frequencies of the two phase-locked loops decrease about 100–200 MHz when subjected to four hours of hot carrier stress. The single-ended VCO gain decreases from 260 MHz to 70 MHz due to hot carrier stress. For the phase-locked loop with the differential voltage-controlled oscillator, a 50 ps RMS jitter increase is observed under hot carrier stress.