Temperature-Compensated Delay Circuits for Stable Ring Oscillators
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Solution Overview
Problem
Integrated circuits, particularly ring oscillators, face a disadvantage in generating clock signals due to increased delay time with temperature, leading to lowered operating frequencies and inability to operate at high speeds or high voltage levels.
Innovation Solution
A delay circuit with a series of delay cells and a variable voltage supplier that adjusts voltage proportionally or inversely to temperature, using loading capacitors with highly-doped N-type impurity regions in an N-well to compensate for temperature-induced delays, allowing operation across a wide voltage range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If bias voltages of MOS transistors are increased to compensate for temperature-induced delay, then delay time is reduced, but voltage operation range is limited and high-speed operation is prevented
Solution Approach 1:
The patent changes the capacitance parameter of the loading capacitor dynamically based on temperature. By using a capacitor with temperature-dependent capacitance (decreasing capacitance at higher temperatures), the RC time constant is adjusted to compensate for temperature-induced delay without requiring changes in bias voltage, thus maintaining wide voltage operation range and enabling high-speed operation
Solution Approach 2:
The patent introduces a loading capacitor as an intermediary element between the inverter output and ground. This capacitor mediates the temperature compensation by its varying capacitance, which indirectly adjusts the delay characteristics without directly modifying the bias voltage or transistor parameters, thereby preserving voltage flexibility
2Reliability
If bias voltages are increased to prevent delay increase, then operating frequency is maintained, but high voltage signals cannot be input or output
Solution Approach 1:
The patent employs temperature-dependent capacitance parameter changes in the loading capacitor to maintain frequency stability. The capacitance decreases with increasing temperature, compensating for the increased RC time constant and maintaining consistent operating frequency across temperature ranges without constraining voltage signal levels
3Temperature
If delay time is increased due to temperature rise, then operating frequency is lowered, but normal operation cannot be maintained without compensation
Solution Approach 1:
The patent utilizes temperature-dependent capacitance parameter changes to compensate for temperature effects. As temperature increases, the capacitor's capacitance decreases, which reduces the RC time constant and prevents operating frequency from dropping, thereby maintaining productivity across wide temperature ranges
Solution Approach 2:
The system provides implicit feedback through the temperature-dependent capacitance characteristic. The capacitance automatically adjusts in response to temperature changes, creating a self-regulating mechanism that maintains frequency stability without external control, ensuring normal operation across temperature variations
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
The solution effectively stabilizes the delay time across temperature variations, enabling high-speed operation and maintaining frequency stability without being limited by voltage ranges, thus improving the performance of integrated circuits.
Implementation Method 1
the at least one loading capacitor including a capacitance that is decreased corresponding to an increase in temperature when a positive voltage is applied across the first end and the second end of the at least one loading capacitor
Data Source
AI summary
Delay circuits are provided. Some embodiments of delay circuits herein include a delay line including multiple delay cells connected in series and a variable voltage supplier operative to output a voltage value proportional and/or inversely proportional to a temperature. Delay circuits may include at least one loading capacitor that includes a first end that is connected to an output port of the delay cell and a second end that is connected to an output port of the variable voltage supplier, the at least one loading capacitor including a capacitance that is decreased corresponding to an increase in temperature when a positive voltage is applied across the first end and the second end of the at least one loading capacitor.