Ring Oscillator Frequency Synthesis With Weak-Inversion Power Control
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Solution Overview
Problem
Conventional ring oscillators require significant area and power, making them less suitable for integration on semiconductor substrates, especially with the trend towards smaller device dimensions and lower supply voltages.
Innovation Solution
A digital frequency locked loop (DFLL) system with a digitally controlled oscillator (DCO) and a low-power decoder that uses a ring oscillator with a variable current mirror and weak inversion structure to reduce power consumption and area requirements by controlling the frequency through voltage adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional ring oscillators are used, then frequency generation is achieved, but area and power consumption increase
Solution Approach 1:
The patent changes the operating parameters of the ring oscillator by using weak inversion operation mode for the inverting stages, which significantly reduces power consumption. The tail current is set to a low value (e.g., 100nA to 10uA) to operate in weak inversion, and the control voltage range is optimized (e.g., 0.2V to 0.8V) to maintain oscillation while minimizing power usage. This parameter optimization allows the oscillator to achieve frequency generation with much lower power consumption compared to conventional strong inversion designs.
2Area of moving object
If device dimensions are reduced, then integration density improves, but ring oscillator area and power requirements increase relative to performance
Solution Approach 1:
The patent optimizes the physical dimensions and electrical parameters of the ring oscillator components to achieve better area-power efficiency. The inverting stages use minimum or near-minimum channel width transistors to reduce area, while the channel length is optimized to maintain adequate gain. The control voltage swing is minimized (e.g., 0.2V to 0.8V) to reduce power consumption. These parameter optimizations enable the oscillator to achieve frequency generation with reduced area and power consumption, making it suitable for modern scaled technologies.
3Power
If supply voltage is reduced, then power consumption decreases, but ring oscillator performance degrades
Solution Approach 1:
The patent operates the ring oscillator in weak inversion with optimized low supply voltages (e.g., 0.2V to 0.8V) to achieve low power consumption. The inverting stages are designed with appropriate transistor aspect ratios and tail current values to maintain sufficient gain and oscillation condition at these low voltages. The control voltage range is carefully selected to provide adequate frequency tuning range while maintaining stable oscillation at the reduced supply voltage. This approach enables the oscillator to achieve both low power consumption and acceptable oscillation frequency performance.
Data Source
AI summary
The present disclosure is directed to a method and apparatus for providing an output oscillating signal at a desired frequency. In at least one example, the apparatus includes a weak inversion structure configured to set a small reference current. A current mirror configured to provide a replica current based on the small reference current and a tuning word. A ring oscillator is configured to be powered by a supply at a voltage determined based on the replica current. The tuning word is adjustable to change the voltage such that the ring oscillator provides the output oscillating signal at the desired frequency.