Low pass filter-less pulse width controlled PLL with zero phase offset using pulse width accumulator

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This paper proposes a pulse width controlled Type-II PLL without using a charge pump nor a RC low pass filter. The loop filter is realized in a pulse width in time-domain instead of an analog voltage in voltage domain. The PLL has a pulse width P-I controlled oscillator whose oscillation frequency is controlled by two pulse widths, one of which is the PFD output pulse width (P), and the other is the integrated pulse width from the PFD output (I). The pulse width controlled oscillator directly converts the input pulses into soft-thermometer codes without a voltage-domain averaging, and the codes control the oscillation frequency. The PLL is designed with 0.18μm CMOS technology, and simulation results show that it consumes 7.2mW with 1.4GHz output frequency under 1.8V supply voltage.