Variable Delay Oscillator Circuit Voltage Compensation
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Solution Overview
Problem
Conventional ring oscillators experience unpredictable variations in oscillation speed due to changes in supply voltage and temperature, which are not adequately addressed by supply voltage regulators, leading to inefficiencies and increased power consumption.
Innovation Solution
Incorporating a variable delay circuit stage in the oscillator circuit that adjusts delay primarily in response to supply voltage changes, while maintaining stability across temperature variations, using a configuration with nFETs and pFETs that provide a proportional delay inversely related to the supply voltage, and employing a capacitance and current mirror to regulate discharge times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a supply voltage regulator is used to regulate the supply voltage to the oscillator stages, then variations in oscillation speed due to supply voltage changes are reduced, but the regulator occupies space on the integrated circuit and consumes power
Solution Approach 1:
The patent extracts the voltage regulation function from a separate regulator circuit and integrates it directly into the oscillator stages by modifying the inverter circuitry. Each inverter stage includes transistors configured to sense supply voltage variations and automatically adjust their operating points, thereby compensating for supply voltage changes without requiring an external regulator.
Solution Approach 2:
The oscillator stages perform dual functions: they generate the oscillation signal and simultaneously regulate the supply voltage effects. The same transistors that form the inverter for signal generation also act as voltage sensing and compensation elements, eliminating the need for dedicated regulator components.
2Device complexity
If the supply voltage regulator is removed to reduce circuit area and power consumption, then oscillation speed variations due to supply voltage changes become large and unpredictable
Solution Approach 1:
The oscillator stages are designed to self-regulate in response to supply voltage variations. Each stage monitors its own supply voltage conditions through the transistor configuration and automatically adjusts its charging and discharging rates to maintain consistent oscillation speed, making the circuit self-compensating without external regulation.
Solution Approach 2:
The transistor configuration creates an implicit feedback mechanism where supply voltage changes are sensed by the inverter stages, which then adjust their operation to counteract the voltage variations. This automatic feedback loop stabilizes oscillation speed without requiring separate control circuitry.
3Productivity
If the supply voltage is increased to increase the oscillation frequency, then the charging and discharging rates of the output node increase, but this creates unpredictable frequency variations
Solution Approach 1:
The patent makes the inverter stages dynamically adaptive to supply voltage conditions. The transistor operating points automatically shift in response to voltage changes, allowing the circuit to maintain optimal performance across a range of supply voltages rather than being fixed at a single operating point.
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 solution stabilizes the oscillation frequency primarily in response to supply voltage changes, reducing frequency variations and power consumption, while maintaining efficiency and reducing noise and area requirements in integrated circuits.
Implementation Method 1
If each stage includes an inverter formed from an n-channel field effect transistor (nFET) and a p-channel field effect transistor (pFET), the frequency of the output signal generally depends on the rate at which each nFET discharges that stage's output node and the rate at which each pFET charges that output node
Implementation Method 2
employing a capacitance and current mirror to regulate discharge times
Data Source
AI summary
Circuits, apparatuses, and methods are disclosed for oscillators. In one such example oscillator circuit, a plurality of delay stages are coupled in series. A variable delay circuit stage is coupled to the plurality of delay stages and is configured to delay a signal through the variable delay circuit stage by a variable delay. The variable delay increases responsive to a rising magnitude of a supply voltage provided to the variable delay circuit stage.