MTJ Ring Oscillator Frequency Tuning via NMOS Threshold Control
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Solution Overview
Problem
Existing tunable-frequency ring oscillators require a larger area on integrated circuits and do not offer a broad range of tuning frequencies, making them unsuitable for highly-scaled integrated circuit designs and power-efficient devices.
Innovation Solution
The implementation of a ring oscillator with an odd number of inverters, each comprising an NMOS transistor and one or more magnetic tunnel junctions (MTJs), where the NMOS transistors are tunable in terms of threshold voltage and effective channel width, and the MTJs can be selectively switched between parallel and anti-parallel states to achieve a wide range of frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional ring oscillators are used for multiple frequency applications, then frequency coverage is limited, but hardware sharing and power efficiency are compromised
Solution Approach 1:
The ring oscillator employs dynamically controllable delay cells where the delay time of each cell can be adjusted in real-time. This is achieved through controllable logic elements that can switch between different conduction states, allowing the oscillation frequency to be tuned across a wide range while maintaining power efficiency through selective activation of delay cells
Solution Approach 2:
The oscillator changes operational parameters by varying the delay time of individual delay cells through control signals. Each delay cell's delay characteristic can be independently adjusted, enabling continuous frequency tuning from approximately 100 MHz to 1 GHz without requiring multiple separate oscillator circuits, thus maintaining hardware sharing and power efficiency
2Adaptability or versatility
If the number of delay cells is increased to extend frequency tuning range, then frequency coverage improves, but circuit area increases
Solution Approach 1:
Instead of adding more static delay cells to extend tuning range, the invention makes existing delay cells dynamic and reconfigurable. Each delay cell can adapt its delay characteristic through control signals, allowing a compact set of delay cells to provide a wide tuning range from 100 MHz to 1 GHz, avoiding the area penalty of adding more cells
Solution Approach 2:
Each delay cell is designed to perform multiple functions by being controllable over a range of delay times. The same physical delay cell structure serves different frequency requirements through dynamic reconfiguration, eliminating the need for multiple dedicated delay cells for different frequency ranges and reducing overall circuit footprint
3Adaptability or versatility
If controllable logic elements are added to each inverter for frequency tuning, then frequency adjustability improves, but device complexity increases
Solution Approach 1:
The oscillator is segmented into multiple independent delay cells, each with its own controllable logic element. This segmentation allows frequency tuning to be achieved by independently controlling each segment rather than requiring a complex global control mechanism, simplifying the overall control architecture while maintaining frequency adjustability
Solution Approach 2:
Controllable logic elements are integrated into each inverter stage, allowing the delay characteristic of each stage to be dynamically adjusted. This dynamic control is achieved through simple control signals that modify the conduction state of transistors within existing inverter structures, avoiding the need for additional complex control circuitry
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 a compact and highly tunable ring oscillator with a broad range of frequencies, suitable for use in various electronic devices, including radio and telecommunications applications, while minimizing the circuit footprint.
Implementation Method 1
the MTJs can be selectively switched between parallel and anti-parallel states to achieve a wide range of frequencies
Data Source
AI summary
Provided are integrated circuits that include one or more magnetic tunnel junction ring oscillator(s) with tunable frequency and methods for operating the same. Accordingly, an integrated circuit is provided that includes a ring oscillator. The ring oscillator includes an input voltage terminal, an output voltage terminal, and an odd number of at least three inverters disposed electrically in series with one another between the input voltage terminal and the output voltage terminal. Each of the at least three inverters includes an NMOS transistor and one or more magnetic tunnel junctions (MTJs) disposed electrically in series with the NMOS transistor. The NMOS transistor of each of the at least three inverters is selectively tunable with regard to either or both of its threshold voltage and its effective channel width.