LC VCO Common-Mode Boost for Reliable Low-Voltage Start-Up
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Solution Overview
Problem
Voltage-controlled oscillators (VCOs) face challenges in starting up reliably in low-voltage deep submicron CMOS technologies due to reduced supply voltage and increased threshold voltages, leading to insufficient gain for oscillation and increased power consumption.
Innovation Solution
Dynamically adjusting the common mode voltage at the LC tank node and/or power supply voltage of a VCO to temporarily increase gain, allowing for robust start-up without impacting frequency tuning range or phase noise, by using a control circuit to monitor and adjust the common mode voltage to exceed transistor threshold voltages during start-up.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If supply voltage is reduced to lower power consumption, then power consumption decreases, but gain becomes insufficient for reliable oscillation start-up
Solution Approach 1:
The patent applies preliminary action by temporarily boosting the common mode voltage at the LC tank node before and during the start-up phase. This preliminary voltage adjustment ensures sufficient gain for reliable oscillation initiation, after which the voltage is reduced to normal operating levels for power-efficient steady-state operation.
Solution Approach 2:
The patent implements dynamics by dynamically adjusting the common mode voltage based on the operational state of the VCO. During start-up, the common mode voltage is temporarily increased to ensure reliable oscillation; during steady-state operation, it is reduced to minimize power consumption. This dynamic adjustment resolves the contradiction between start-up reliability and power efficiency.
2Loss of energy
If threshold voltage is increased to reduce leakage current, then leakage power reduces, but gain becomes insufficient for oscillation start-up
Solution Approach 1:
The patent applies preliminary action by temporarily boosting the common mode voltage at the LC tank node before and during the start-up phase. This preliminary voltage adjustment ensures sufficient gain for reliable oscillation initiation, after which the voltage is reduced to normal operating levels for power-efficient steady-state operation.
Solution Approach 2:
The patent implements dynamics by dynamically adjusting the common mode voltage based on the operational state of the VCO. During start-up, the common mode voltage is temporarily increased to ensure reliable oscillation; during steady-state operation, it is reduced to minimize power consumption. This dynamic adjustment resolves the contradiction between start-up reliability and power efficiency.
3Reliability
If common mode voltage is increased to ensure reliable start-up, then oscillation start-up reliability improves, but power consumption increases
Solution Approach 1:
The patent applies preliminary action by temporarily boosting the common mode voltage at the LC tank node before and during the start-up phase. This preliminary voltage adjustment ensures sufficient gain for reliable oscillation initiation, after which the voltage is reduced to normal operating levels for power-efficient steady-state operation.
Solution Approach 2:
The patent applies periodic action by implementing a time-dependent common mode voltage adjustment strategy. During the start-up period, the common mode voltage is temporarily increased to ensure reliable oscillation; once steady-state is achieved, the voltage returns to normal levels. This periodic adjustment pattern minimizes power consumption while ensuring reliable start-up.
4Adaptability or versatility
If transistor size is reduced to increase frequency tuning range, then frequency tuning range increases, but gain becomes insufficient for reliable start-up
Solution Approach 1:
The patent applies preliminary action by temporarily boosting the common mode voltage at the LC tank node before and during the start-up phase. This preliminary voltage adjustment ensures sufficient gain for reliable oscillation initiation, after which the voltage is reduced to normal operating levels for power-efficient steady-state operation.
Solution Approach 2:
The patent implements dynamics by dynamically adjusting the common mode voltage based on the operational state of the VCO. During start-up, the common mode voltage is temporarily increased to ensure reliable oscillation; during steady-state operation, it is reduced to minimize power consumption. This dynamic adjustment resolves the contradiction between start-up reliability and power efficiency.
Data Source
AI summary
The present disclosure provides methods and apparatus for dynamically adjusting the common mode voltage at the LC tank node and/or the power supply voltage of a VCO with an LC resonator in order to force oscillation start-up by temporarily increasing gain. Methods according to certain preferred embodiments may reduce power consumption and/or overcome threshold voltage limitations and/or increase frequency and frequency tuning range during normal (steady-state) operation.