PLL Transmission Switch Leakage Removal for Fine Lock Stability
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Solution Overview
Problem
The reduction of power supply voltage in electronic devices leads to increased leakage current through transmission switches in phase locked loop circuits, affecting the control voltage and resulting in imprecise synchronization of output signals in fine lock modes.
Innovation Solution
Incorporating a leakage remover circuit that maintains equal voltages at both terminals of the transmission switch or connects to one side to significantly reduce leakage current, allowing the phase locked loop circuit to operate with a desired turn-on resistance without increasing switch size, and using a buffer or voltage divider to block leakage current in fine lock modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the power supply voltage is reduced, then power consumption is decreased, but leakage current through transmission switches increases
Solution Approach 1:
The patent extracts and removes the harmful leakage current from the system by introducing a leakage remover circuit that actively compensates for and eliminates the leakage current generated by transmission switches during voltage reduction, allowing low voltage operation without suffering from increased leakage
Solution Approach 2:
The patent introduces a buffer circuit as an intermediary element between the transmission switch and the control voltage node. This buffer acts as a mediator that blocks the propagation of leakage current while allowing the transmission switch to maintain its low resistance state during normal operation
2Reliability
If the size of transmission switch is increased, then turn-on resistance is decreased, but leakage current increases
Solution Approach 1:
The patent segments the transmission switch into two independent components: the main transmission switch that handles signal transmission with optimized dimensions for low on-resistance, and a separate leakage remover circuit that independently handles leakage current compensation. This segmentation allows each component to be optimized for its specific function without compromise
Solution Approach 2:
The buffer circuit serves as an intermediary that decouples the relationship between transmission switch size and leakage current. It allows the transmission switch to be sized for optimal turn-on resistance while the buffer blocks the leakage current path, preventing the usual trade-off between these two parameters
3Loss of energy
If transmission switch is turned off, then power consumption is reduced, but leakage current affects control voltage
Solution Approach 1:
The buffer circuit acts as an intermediary barrier that blocks leakage current from reaching the control voltage node when the transmission switch is turned off. This allows the transmission switch to remain in high-impedance state for low power consumption while the buffer prevents leakage current from degrading control voltage stability
Solution Approach 2:
The leakage remover circuit implements a feedback mechanism that continuously monitors and compensates for leakage current effects on the control voltage. By detecting voltage deviations caused by leakage and actively correcting them, the system maintains control voltage stability even when power consumption is minimized through switch shutdown
Data Source
AI summary
A phase locked loop circuit includes a voltage controlled oscillator configured to output a clock signal having a predetermined frequency based in a control voltage, a phase frequency detector configured to compare the clock signal with a reference signal to output a first control signal and a second control signal, a charge pump configured to output the control voltage based on the first control signal and the second control signal, a voltage supply including an output terminal connected to an output terminal of the charge pump by a transmission switch, and a leakage remover circuit connected to the transmission switch and configured to remove a leakage current flowing through the transmission switch while the transmission switch is turned-off.