Resistor-Coupled Ring Oscillator for Low-Voltage Operation
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Solution Overview
Problem
Ring oscillators are not amenable to low supply voltage applications due to the requirement of a sufficiently high supply voltage for maintaining oscillation gain.
Innovation Solution
A ring oscillator design incorporating multiple stages with MOS transistors of different types and resistors in a cascaded ring topology, where each stage has a preceding, succeeding, alternate-preceding, and alternate-succeeding stage, with the MOS transistors configured to receive and output voltages and the resistors providing coupling and level-shifting, extending the duty ratio of the MOS transistors to compensate for low supply voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conventional ring oscillator with inverters is used, then oscillation gain is maintained at high supply voltage, but the oscillator cannot operate at low supply voltage
Solution Approach 1:
The patent changes the operating parameters of the ring oscillator by replacing conventional inverters with cross-coupled transistor pairs (NMOS and PMOS) and adding resistive loading. This parameter change allows the oscillator to maintain sufficient gain at low supply voltages where conventional inverters would fail to oscillate
Solution Approach 2:
The patent introduces resistors as intermediary elements connected to the drains of the cross-coupled transistor pairs. These resistors provide additional gain and help maintain oscillation at low supply voltages by acting as mediators that compensate for the reduced transistor drive capability
2Use of energy by moving object
If the supply voltage is reduced for low-power application, then power consumption decreases, but the oscillation frequency and charge output are insufficient
Solution Approach 1:
The patent modifies the circuit parameters by using cross-coupled transistor pairs with resistive loading, which changes the voltage-current characteristics to maintain adequate charge output and oscillation frequency even at reduced supply voltages for low-power operation
Solution Approach 2:
The patent creates a dynamic balance between the cross-coupled transistors and resistive loads that adapts to low supply voltage conditions, allowing the oscillator to maintain productivity (oscillation frequency and charge output) while operating at lower power consumption levels
3Speed
If NMOS and PMOS transistors are directly connected in contention configuration, then circuit speed is maintained, but power is wasted due to contention
Solution Approach 1:
The patent introduces resistors as intermediary elements between the cross-coupled transistor pairs, which mediate the interaction between NMOS and PMOS transistors. This prevents direct contention while maintaining circuit speed by providing controlled current paths
Solution Approach 2:
The patent converts the potential harmful effect of transistor contention into a beneficial configuration by using cross-coupled pairs with resistive loading. The resistors transform the contention scenario into a controlled operation that maintains speed while reducing power waste through improved voltage utilization
Data Source
AI summary
A circuit includes multiple stages cascaded in a ring topology such that each stage has a preceding stage, a succeeding stage, an alternate-preceding stage, and an alternate-succeeding stage. Each stage includes a MOS transistor of a first type, a MOS transistor of a second type and a resistor. The MOS transistor of a first type receives a first input that is output from the preceding stage, and outputs a second output to the alternate-preceding stage. The MOS transistor of a second type receives a second input that is output from the alternate-succeeding stage, and outputs a first output to the succeeding stage. The resistor provides coupling and level-shifting between the first output and the second output.