A 90nm, low power VCO with reduced KVCO and sub-band spacing variation

In this paper we present the design of a low power VCO with reduced variations in VCO gain (KVCO) and sub-band spacing resolution (fres). The proposed VCO is designed using a 90nm CMOS process to cover a tuning range of 23%. Variations in KVCO and fres are reduced by factors of 6 and 17 respectively over a conventional sub-banded VCO, designed using the same process, to meet the same tuning range. This makes the proposed VCO more suited to stable PLL operation with its reduced KVCO requirements resulting in an improvement in phase noise performance over the conventional VCO by 2 dB. Due to the reduced loading on the VCO tank achieved by the presented design, power consumption is kept extremely low at 850 μW from a 1 V supply.

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