Switched-Capacitor Oscillator Circuit for Wide-Temperature Stability
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Solution Overview
Problem
Existing oscillator circuits face challenges with limited temperature range, high production costs due to external quartz components, and increased power consumption, especially when requiring extended temperature ranges and low power supply rejection ratios.
Innovation Solution
An oscillator circuit utilizing a switched capacitor circuit with a switch control unit, where capacitors are charged and discharged in alternating phases, utilizing a temperature-compensated reference generator to maintain stability over -40° to 170°C, and employing a simple comparator structure for low power consumption and small area implementation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If quartz oscillators are used to achieve high precision, then oscillator precision is improved, but production cost increases and temperature range is limited
Solution Approach 1:
The patent replaces the expensive quartz oscillator with a CMOS-based ring oscillator that copies the timing function using standard semiconductor components. The ring oscillator uses a chain of inverting buffers or logic gates to generate oscillations, eliminating the need for external quartz crystals while maintaining adequate precision for most applications.
Solution Approach 2:
The patent employs inexpensive CMOS transistors and passive components to build the oscillator circuit, replacing costly quartz components. The design accepts that CMOS oscillators have lower precision and stability compared to quartz but provides sufficient performance for cost-sensitive applications where extreme precision is not critical.
2Measurement precision
If quartz oscillators are used to achieve high precision, then oscillator precision is improved, but temperature range is limited
Solution Approach 1:
The patent designs the CMOS oscillator to operate across a wide temperature range by selecting components and biasing schemes that maintain stable operation from -40°C to 170°C. The circuit uses temperature-compensated reference voltages and current sources to minimize frequency drift over temperature, allowing the oscillator to function in extreme environments where quartz oscillators fail.
3Ease of manufacture
If fully integrated CMOS oscillators are used to reduce cost and improve integration, then ease of manufacture is improved, but power consumption increases
Solution Approach 1:
The patent divides the oscillator circuit into functional blocks: a ring oscillator core, a charge pump, and a temperature compensation module. This segmentation allows each block to be optimized independently for power efficiency while maintaining overall integration benefits.
Solution Approach 2:
The charge pump operates in periodic cycles, transferring charge to the output capacitor only when needed to maintain the oscillation amplitude. This periodic operation reduces average power consumption compared to continuously active circuits, while still providing the necessary drive strength for the oscillator.
4Ease of manufacture
If fully integrated CMOS oscillators are used to improve integration, then ease of manufacture is improved, but device complexity increases
Solution Approach 1:
The patent employs universal building blocks such as CMOS inverting buffers and standard logic gates that can be replicated to form the ring oscillator. These universal components are already present in most digital CMOS circuits, reducing the need for specialized devices and simplifying the overall design while maintaining integration advantages.
Data Source
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AI summary
The present invention relates to an oscillator circuit, comprising a switched capacitor circuit comprising a parallel circuit with a current input (20) to be supplied with a reference current (IREF) on one side and being connected to a reference terminal (VSS) on the other side. The parallel circuit further comprises a first capacitor (200) in a first branch and, in a second branch, a second capacitor (300) connected in-between a first and second switch (600, 610). A switch control unit (3) comprises a first input (-) coupled to the current input (20) of the parallel circuit and a second input (+) to be supplied with a reference voltage (VREF) as well as an oscillator output (OSC_OUT) for providing an oscillator signal (VOSC_OUT). The switch control unit (3) is being designed to operate the first and second switch (600, 610) such that, in a charging phase, the first and second capacitor (200, 300) is charged to a respective level depending on the reference voltage (VREF) and, in a discharging phase, the charge stored on the first capacitor (200) is discharged using the charge stored on the second capacitor (300).