RC Oscillator Circuit With Switched Capacitors for Stable Frequency
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Solution Overview
Problem
Conventional RC oscillators face challenges in maintaining accurate and constant frequency due to temperature dependencies and trade-offs between reset speed and leakage current, as well as comparator delays, which affect oscillation period and stability.
Innovation Solution
The oscillator circuit incorporates a resistor-capacitor (R-RC) configuration with switched capacitors and additional resistors to cancel second-order temperature dependencies, uses a feedback loop to adjust comparator delays, and employs a switched capacitor circuit to minimize leakage current, ensuring consistent frequency across varying temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional RC oscillator is used, then the circuit can be implemented on a semiconductor chip, but the frequency accuracy deteriorates due to temperature dependency of resistance
Solution Approach 1:
The patent changes the electrical parameters by introducing switched capacitors that are controlled to switch between different capacitance values based on temperature conditions. This allows the RC time constant to be adjusted dynamically, compensating for temperature-induced resistance changes and maintaining frequency accuracy while keeping the oscillator implementable on a semiconductor chip.
Solution Approach 2:
The patent makes the capacitor value dynamic by using switched capacitors that can change their effective capacitance according to temperature. This dynamic adjustment mechanism allows the circuit to adapt to temperature variations, resolving the contradiction between fixed on-chip implementation and variable frequency accuracy across different temperatures.
2Loss of energy
If the reset switch is made larger to reduce leakage current, then leakage current is minimized, but the reset speed deteriorates
Solution Approach 1:
The patent employs periodic switching of capacitors in a multi-capacitor configuration. By periodically switching between different capacitors during the oscillation cycle, the system achieves both low leakage current (when capacitors are properly discharged) and fast reset speed (through the periodic recharging mechanism), eliminating the need for a single large reset switch.
Solution Approach 2:
The patent segments the single capacitor into multiple switched capacitors that operate in sequence. This segmentation allows different capacitors to be charged and discharged at different times, reducing the leakage current impact while maintaining fast reset capability through the segmented charging/discharging process, without requiring a large reset switch.
3Measurement precision
If the comparator delay is reduced to improve frequency accuracy, then frequency stability improves, but power consumption increases
Solution Approach 1:
The patent uses multiple capacitors that are switched in parallel to effectively reduce the impact of comparator delay. By having redundant capacitor paths, the system can tolerate longer comparator delays without significant frequency accuracy degradation, thus allowing the use of lower-power comparators with longer propagation delays while maintaining frequency stability.
Solution Approach 2:
The patent employs excessive action by using more capacitors than the minimum single capacitor would require. This redundancy allows the system to compensate for comparator delay effects, enabling the use of lower-power comparators with longer delays while maintaining the required frequency accuracy through the additional capacitor switching paths.
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 achieves an oscillation signal with accurate and constant frequency, minimizing power consumption and leakage current influence, even at extreme temperatures, while maintaining frequency stability and reducing external factor impacts.
Implementation Method 1
a first capacitor having a first terminal connected to the second resistor; a first transistor having a drain connected to a second terminal of the first capacitor
Implementation Method 2
a first transistor having a drain connected to a second terminal of the first capacitor, a source connected to ground, and a gate suitable for receiving a first transition clock signal
Implementation Method 3
a comparator configured to compare a voltage level to be compared obtained from the resistor circuit with a predetermined reference
Data Source
AI summary
Disclosed an oscillator circuit device includes: a resistor circuit comprising a first resistor disposed between a first supply voltage level and an output node; a resistor-capacitor circuit comprising a second resistor and at least one capacitor disposed between the output node and a second supply voltage level and connected in series, and a switch capable of discharging electric charges accumulated in the at least one capacitor; and a comparator configured to compare a voltage level to be compared obtained from the resistor circuit with a predetermined reference to allow the switch to be opened and closed according to a comparison result.