DocumentCode :
986868
Title :
Performance degradation of LC-tank VCOs by impact of digital switching noise in lightly doped substrates
Author :
Soens, Charlotte ; Van der Plas, Geert ; Wambacq, Piet ; Donnay, Stéphane ; Kuijk, Maarten
Author_Institution :
IMEC, Leuven, Belgium
Volume :
40
Issue :
7
fYear :
2005
fDate :
7/1/2005 12:00:00 AM
Firstpage :
1472
Lastpage :
1481
Abstract :
In mixed analog-digital designs, digital switching noise is an important limitation for the performance of analog and RF circuits. This paper reports a physical model describing the impact of digital switching noise on LC-tank voltage-controlled oscillators (VCOs) in lightly doped substrates. The model takes into account the propagation from the source of substrate noise to the different components in the VCO and the resulting modulation of the oscillator frequency. The model is validated with measurements on a 3.5-GHz LC-tank VCO designed in 0.18-μm CMOS. It reveals that for this VCO, impact occurs mainly via the nonideal metal ground lines for lower frequencies and low tuning voltage and via the integrated inductors for higher frequencies and high tuning voltage. To make the design immune to substrate noise, the parasitic resistance of the on-chip ground interconnect has to be kept as low as possible and inductors have to be shielded. Hence, the developed model allows investigating the dominant mechanisms behind the impact of substrate noise on a VCO, which is crucial information for achieving a substrate noise immune design.
Keywords :
CMOS integrated circuits; integrated circuit modelling; integrated circuit noise; mixed analogue-digital integrated circuits; radiofrequency integrated circuits; voltage-controlled oscillators; 0.18 micron; 3.5 GHz; CMOS integrated circuits; LC-tank VCO; RF circuit; analog circuit; digital switching noise; integrated circuit models; integrated inductors; mixed analog-digital designs; modulation; on-chip ground interconnect; oscillator frequency; substrate noise immune design; voltage-controlled oscillators; Analog-digital conversion; Circuit noise; Degradation; Inductors; Optical propagation; Radio frequency; Semiconductor device modeling; Switching circuits; Tuning; Voltage-controlled oscillators; CMOS integrated circuits; crosstalk; mixed analog–digital integrated circuits; modeling; voltage-controlled oscillators (VCOs);
fLanguage :
English
Journal_Title :
Solid-State Circuits, IEEE Journal of
Publisher :
ieee
ISSN :
0018-9200
Type :
jour
DOI :
10.1109/JSSC.2005.847301
Filename :
1458990
Link To Document :
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