trond
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Yawei,
Thanks for your feedback. I know that the implementation of the VCO dictates the power consumption. But considering only a ring oscillator made up of N single-ended inverter cells, then would it not be right to assume that P=Vd2CLFvco_ave is approx. valid?
You said that " The power consumption of VCOs depends on its design but not acquistion or steady state." But the time required for the PLL to lock to a new frequency can be expressed as taqu = tcapture + tlock . For the estimation of the power consumption during the capture process, I assumed that the VCO frequency follows the variation on the control voltage. Thus, P=Vd2CLFvco_ave where Fvco_ave is the difference between the start frequency, and the end frequency. The locked condition can be considered a stable state. There are no drastic changes and most of the variables like Kvco and fvco are constant. To estimate the power during the locked range I consider that for a non-differential implementation, at any given time, just one cell is switching. Thus the current would be something like I=VddCL/td where td=1/2/N/fvco.
Out of curiosity, how would you model the power consumption of a ring-osc. during aquisition range?
Cheers,
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