Digitally Tunable Relaxation Oscillator for Stable Clock Frequency
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Solution Overview
Problem
As integrated circuits become more complex and clock frequencies increase, managing timing and maintaining a stable frequency of oscillation signals becomes increasingly difficult due to variations in operating conditions such as supply voltage and temperature.
Innovation Solution
A relaxation oscillator with a dynamically controllable current source, including a digitally tunable current mirror with transistors that can be selectively connected in parallel to adjust current, is used to maintain a stable oscillation frequency by sensing and compensating for changes in operating conditions through a system monitor and calibration logic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If clock frequency is increased to improve performance, then productivity is improved, but timing control becomes more difficult and frequency stability deteriorates
Solution Approach 1:
The current source is made dynamically controllable through a digitally tunable current mirror with multiple transistors that can be selectively connected in parallel. This dynamic structure allows real-time adjustment of the current magnitude in response to operating conditions, enabling frequency stabilization even at high clock frequencies where traditional fixed current sources would fail to maintain stability
Solution Approach 2:
The invention changes the electrical parameters (current magnitude) of the oscillator based on detected operating conditions such as temperature and supply voltage variations. By dynamically adjusting the current source parameters, the system compensates for environmental changes and maintains stable oscillation frequency despite operating at higher clock frequencies
2Reliability
If circuit complexity is increased to enable dynamic control of operating conditions, then frequency stability is improved, but device complexity increases
Solution Approach 1:
The current source is segmented into multiple parallel transistor branches, each controllable independently. This segmentation allows selective activation of specific transistor paths based on operating conditions, providing fine-grained control over the current magnitude without requiring a completely complex redesign of the entire circuit
Solution Approach 2:
The digitally tunable current mirror structure serves multiple functions: it acts as the primary current source for the relaxation oscillator, provides dynamic adjustability for frequency stabilization, and can adapt to various operating conditions (temperature, voltage) through a unified control mechanism, reducing the need for separate compensation circuits
Data Source
AI summary
Examples described herein provide for a relaxation oscillator and corresponding methods of operation. In an example, a circuit includes a dynamically controllable current source, a capacitor, and an oscillator generation circuit. The dynamically controllable current source includes a digitally tunable current mirror configured to generate a current. The digitally tunable current mirror includes multiple transistors configured to be selectively electrically connected in parallel to alter a gain of the digitally tunable current mirror to control the current. The capacitor is selectively electrically connected to the dynamically controllable current source. The oscillator generation circuit is electrically connected to the capacitor. The oscillator generation circuit is configured to generate an oscillation signal in response to a voltage of the capacitor.