Switch-Reconfigured Oscillator Circuit for Low-Frequency RTC Timing
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Solution Overview
Problem
Conventional on-chip oscillator circuits require larger resistive and capacitive elements for low oscillation frequencies, limiting their application, especially in real-time clock systems, due to higher area requirements and reduced frequency accuracy.
Innovation Solution
The proposed oscillator circuit employs a switch control circuit to adjust the connection relationships between constant current sources, capacitive elements, and a resistive element, allowing for a smaller RC time constant and reduced area by switching the connections based on comparator outputs, thereby reducing the size of the resistive and capacitive elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional on-chip oscillator circuit uses larger resistive and capacitive elements to achieve low oscillation frequency, then the oscillation frequency accuracy is improved, but the circuit area increases
Solution Approach 1:
The patent applies dynamics by making the oscillator circuit configuration changeable through switch control. The switch control circuit dynamically reconfigures the connection relationships between constant current sources, capacitive elements, and the resistive element based on comparator outputs, allowing the circuit to adapt its RC time constant rather than requiring fixed large components for low frequencies
Solution Approach 2:
The patent changes the RC time constant parameter by reconfiguring the circuit connections. By switching between different connection states of the capacitive elements and current sources, the effective RC time constant is adjusted to achieve low oscillation frequencies without requiring physically large resistive and capacitive elements, thus maintaining frequency accuracy while reducing circuit area
2Measurement precision
If the oscillation frequency is reduced for real-time clock applications, then the frequency accuracy requirement increases, but the RC time constant requires larger components
Solution Approach 1:
The circuit uses dynamic reconfiguration through switches to change the RC time constant based on operating conditions. The switch control circuit responds to comparator outputs and reconfigures the connection relationships, enabling the same circuit to achieve different effective RC time constants without changing the physical size of the resistive and capacitive elements
Solution Approach 2:
The patent changes the effective RC time constant parameter by reconfiguring which capacitive elements are connected to which current sources. This parameter change allows the circuit to achieve the required time constants for low frequency real-time clock applications without using larger physical components, thus maintaining frequency accuracy while reducing component quantity and size
3Duration of action of moving object
If larger resistive and capacitive elements are used to achieve low oscillation frequency, then the oscillation period is extended, but the circuit area and component size increase
Solution Approach 1:
The patent makes the oscillator circuit dynamically reconfigurable using switch control. The switch control circuit changes the connection relationships between circuit elements based on comparator outputs, allowing the circuit to extend its oscillation period through control logic rather than by increasing the physical size of resistive and capacitive elements
Solution Approach 2:
The patent changes the effective RC time constant parameter by reconfiguring the circuit topology. By switching between different connection states, the circuit achieves the required extended oscillation period for low frequency applications without proportionally increasing the area of the resistive and capacitive elements, thus decoupling oscillation period from component area
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 achieves a smaller RC time constant and reduced area for the oscillator circuit, improving frequency accuracy and reducing the contribution of comparator delay time to the oscillation period, leading to a more compact and accurate oscillator design.
Implementation Method 1
charges a capacitor by the other constant current. Here, the voltage of the capacitor rises in proportion to time
Implementation Method 2
The comparator compares the voltages of the capacitance with the reference voltage, and based on the comparison result, a clock signal is generated
Implementation Method 3
when the oscillation period is T, and the resistance value of the resistive element is R, and the capacitance value of the capacitive element is C, the oscillation period T is twice the product of resistance value R and capacitance value C
Data Source
AI summary
A small area oscillator circuit is provided. The oscillator circuit includes first and second constant current sources, a comparator, first and second capacitive elements, and a resistive element. In a first state, the first capacitive element is connected to the first constant current source and the fixed voltage node, the second capacitive element is connected to the second constant current source and the first current source, and resistive element is connected to the second constant current source. In a second state, the first capacitive element is connected to the second constant current source and first constant current source, the second capacitive element is connected to the second constant current source and the fixed voltage node, and the resistive element is connected to the first constant current source.