Low-noise wideband PLL with dual-mode ring-VCO

Abstract

A low-jitter 110 MHz-to-620 MHz phase-locked loop (PLL) that includes a low-noise wide-frequency-range ring oscillator with a dual-mode operation is presented. The measurement results using a 65 nm low-power CMOS process show that the proposed PLL achieves as low as a 2.5 ps RMS jitter at 600 MHz of output frequency while consuming 2.7 mW at a 1.2 V supply. The die area is only 0.09 mm 2 .Introduction: Because of the increase in digital/analogue processing and communication systems and the tendency to integrate whole systems in a single chip, the demand for small-size, low-power phaselocked loops (PLLs) is increasing. The VCO (voltage-controlled oscillator) of the PLLs is the key block because its phase noise directly affects the quality of the output signal. Among diverse structures for the VCO realisation, a ring oscillator is attractive owing to its wide frequency range, low-voltage operation, multiple output phases generation, and easy integration in a standard CMOS process. However, ring oscillators generally show poor phase noise performance and high power consumption because of these low effective quality factors. To overcome these difficulties, several topologies have been proposed [1][2][3][4]. Nevertheless, the power dissipation is the critical issue in most cases. In this Letter, a small-size and low-power PLL is proposed by adopting a varactor-based low-noise ring-VCO.

A 3.8-GHz highly linear <i>LC</i>-VCO without a varactor device

“…Many papers discussed mainly about a low phase noise [1, 2, 3, 4, 5], but a linear tuning scheme is reported in only few papers. In addition, most of the VCOs have a nonlinear frequency tuning by using a varactor [1,2,3,4], which degrades the settling behavior of a PLL. For this reason, it is desirable to have a linear tuning characteristic.…”

an 800‐MHz LC‐VCO with a Linear Control Characteristics in a 130‐nm CMOS Technology

“…The nonlinear frequency tuning degrades the settling behavior and the overall phase noise of a phase‐locked loop . Many articles mainly utilized for a nonlinear frequency tuning due to the capacitance characteristics of varactor diodes, but a linear tuning scheme is reported in only few articles .…”

V – I converter‐based voltage‐controlled oscillator with improved linear gain characteristic

“…One study proposed an approach to reduce the supply noise sensitivity but failed to secure a linear VCO gain [4]. Other works used a multiple-path ring oscillator to achieve a high-speed characteristic but failed to secure a linear gain characteristic and a wide operating frequency range [5,6].To solve all of the mentioned problems, this Letter proposes a voltage-current (V-I) converter-based VCO instead of the supply-power-regulated VCO. The newly designed VCO has a linear gain characteristic within a wide control voltage (V ctrl ) range, and it has a full supply transition output with a small area and low power dissipation.…”

“…One study proposed an approach to reduce the supply noise sensitivity but failed to secure a linear VCO gain [4]. Other works used a multiple-path ring oscillator to achieve a high-speed characteristic but failed to secure a linear gain characteristic and a wide operating frequency range [5,6].…”

“…To avoid the above-mentioned problems, the works in [4][5][6] used a ring VCO that maintains a full supply voltage swing without regulating the VCO power. One study proposed an approach to reduce the supply noise sensitivity but failed to secure a linear VCO gain [4].…”