PLL Loop Filter With Oxide Transistor for Fast Standby Re-Lock
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Solution Overview
Problem
Phase locked loops face challenges in achieving both high stability and response characteristics, and when transitioning from a stand-by state, there is a trade-off between stability and response, leading to increased power consumption and longer stabilization times.
Innovation Solution
Incorporating an oxide semiconductor transistor between the voltage controlled oscillator and the capacitor in the loop filter, which is turned off during stand-by to conserve power and quickly turned on to re-establish a stable voltage signal upon return from stand-by.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the phase locked loop uses a conventional loop filter with continuous operation of the charge pump and voltage controlled oscillator during stand-by, then the voltage signal stability is maintained, but power consumption increases and the stabilization time after returning from stand-by is extended
Solution Approach 1:
The charge pump and voltage controlled oscillator are operated periodically rather than continuously. During stand-by mode, these components are stopped to reduce power consumption, and only the oxide semiconductor transistor remains active to maintain the voltage signal on the capacitor. When returning from stand-by, the components are restarted periodically to re-establish the locked state, eliminating the need for continuous operation and reducing overall power consumption while maintaining stability during idle periods.
2Use of energy by moving object
If the charge pump and voltage controlled oscillator are stopped during stand-by to reduce power consumption, then power consumption is reduced, but the voltage signal becomes unstable and requires longer stabilization time after returning from stand-by
Solution Approach 1:
The oxide semiconductor transistor serves as an intermediary component between the charge pump/voltage controlled oscillator and the capacitor. It maintains the voltage signal on the capacitor during stand-by by blocking charge leakage, acting as a mediator that preserves the electrical state without requiring continuous operation of the power-consuming components. This intermediary function enables rapid recovery after stand-by since the capacitor retains its charge, eliminating the need for lengthy stabilization periods when the system resumes operation.
3Ease of manufacture
If a conventional transistor is used in the loop filter, then the circuit can be easily manufactured, but the transistor cannot effectively maintain charge on the capacitor during stand-by due to leakage current
Solution Approach 1:
The transistor's key parameter - the off-state current - is changed from conventional levels (high leakage) to extremely low levels (1aA or less) by using oxide semiconductor material. This parameter change enables the transistor to effectively maintain charge on the capacitor during stand-by operation. The manufacturing process remains compatible with conventional semiconductor fabrication techniques, so the ease of manufacture is preserved while achieving superior charge holding capability through material parameter optimization.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration allows for rapid re-locking of the phase locked loop after stand-by and reduces power consumption by maintaining charge on the capacitor, thereby shortening stabilization time and minimizing power wastage.
Implementation Method 1
the transistor includes a semiconductor layer including an oxide semiconductor material... the transistor is turned off... the potential (electric charge) of the capacitor is lost... the transistor is turned on... the voltage signal input to the voltage controlled oscillator becomes constant in a short time
Data Source
AI summary
It is an object of the present invention to provide a phase locked loop in which a voltage signal input to a voltage controlled oscillator after a return from a stand-by state becomes constant in a short time and power consumption is reduced. A transistor including a semiconductor layer formed using an oxide semiconductor material is provided between an input terminal of a voltage controlled oscillator and a capacitor of a loop filter. The transistor is turned on in a normal operation state and turned off in a stand-by state.