Micropower RC Oscillator With Current-Mirrored Inverter Drive
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Solution Overview
Problem
Conventional RC oscillators in mobile systems face high current consumption, instability due to temperature and process changes, and high implementation costs, limiting battery life and requiring large passive elements, which restricts system-on-chip integration and stability.
Innovation Solution
A micropower RC oscillator design that includes a current generating section with a variable resistor for self-temperature compensation, a start-up circuit to stabilize the bias operating point, and a charge and discharge circuit with a variable capacitor, along with an inverter driving power supply section that mirrors the current source, reducing power consumption and enhancing stability across temperature and process variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the power supply voltage is directly applied as a driving power supply of the inverters, then the oscillation signal can be generated, but the current consumption increases
Solution Approach 1:
A current mirror circuit is introduced as an intermediary between the power supply voltage and the inverters. The current mirror circuit generates a controlled current that drives the inverters, replacing the direct voltage application. This intermediary structure enables oscillation signal generation while precisely controlling the current consumption to reduce power usage.
2Device complexity
If resistance and capacitance are fixed values, then the circuit is simple, but the frequency cannot be changed and system-on-chip integration is difficult
Solution Approach 1:
The patent replaces fixed resistance and capacitance values with dynamically adjustable components. A variable resistor and variable capacitor are introduced, allowing their values to be changed through control signals. This dynamic configuration enables frequency adjustment while maintaining relatively simple circuit structure, facilitating system-on-chip integration.
3Ease of manufacture
If the RC oscillator is used for mass productivity, then the cost is reduced, but the operation characteristics become unstable with temperature and process changes
Solution Approach 1:
A feedback mechanism is introduced to compensate for temperature and process variations. The circuit monitors the oscillation frequency and adjusts the variable resistor and capacitor values through feedback control signals. This feedback system maintains stable operation characteristics across different temperatures and manufacturing processes while keeping the circuit suitable for mass production.
4Ease of manufacture
If passive elements with large size are disposed in chip, then the RC oscillator can be implemented, but the chip area increases and system-on-chip integration is restricted
Solution Approach 1:
The patent changes the parameters of the passive elements from fixed large values to variable smaller values. By using variable resistor and capacitor with smaller physical sizes that can be adjusted through control signals, the chip area is reduced. The variable nature allows maintaining the required RC time constant for oscillation while using compact elements suitable for system-on-chip integration.
Data Source
AI summary
A micropower RC oscillator comprises a current generating section including a current source that generates a current; and a variable resistor of which the magnitude is variably set and which is configured by combining resistor elements at a predetermined ratio, the resistor elements having opposite characteristics to each other with respect to a temperature change, the variable resistor adjusting the magnitude of the generated current; a start-up circuit section connected to the current generating section and fixing a bias operating point to a constant value such that the current generating section stably generates a current; a charge and discharge circuit section including a variable capacitor, of which the magnitude is variably set, and a plurality of transistors, the charge and discharge circuit section charging and discharging the variable capacitor by using the current generated from the current generating section and the plurality of transistors; an oscillation signal output section connected to the charge and discharge circuit section and including a plurality of inverters, the oscillation signal output section outputting an oscillation signal of which the frequency is determined by the resistance of the variable resistor and the capacitance of the variable capacitor; and an inverter driving power supply section mirroring the current generated from the current generating section and then providing the mirrored current as a driving power supply of the inverters.