Oscillator Circuit Frequency Stability via Time-Sharing Current Distribution
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Solution Overview
Problem
The feedback loop type oscillator integrated on a semiconductor chip faces challenges in maintaining high frequency stability accuracy due to variations in reference currents generated by a current mirror circuit, which are affected by process variations, temperature fluctuations, and power supply voltage fluctuations.
Innovation Solution
An oscillator circuit design that includes a frequency variable oscillator, a reference current source, a path selector to distribute the reference current in a time-sharing manner, an F/V conversion circuit with a capacitor, a reference voltage source with a resistor, and a feedback circuit to adjust the control signal, ensuring equal reference currents and using a clocked comparator to eliminate system offset.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a feedback loop type oscillator is integrated on a semiconductor chip, then the oscillator can be manufactured using standard semiconductor processes, but frequency stability accuracy deteriorates due to variations in reference currents from the current mirror circuit
Solution Approach 1:
The patent divides the reference current distribution into separate first and second paths, with the second path further divided into multiple sub-paths. This segmentation allows independent control and compensation of current variations in each path, improving frequency stability while maintaining integrability on semiconductor chips.
Solution Approach 2:
The patent employs a feedback mechanism where detection voltages from multiple paths are compared with reference voltages, and control signals are generated to adjust the reference current distribution. This feedback loop compensates for current variations caused by process, temperature, and voltage fluctuations, thereby improving frequency stability accuracy.
2Ease of manufacture
If reference currents are distributed through a current mirror circuit, then the oscillator can be integrated on a semiconductor chip, but frequency stability accuracy deteriorates due to process variations, temperature fluctuations, and power supply voltage fluctuations
Solution Approach 1:
The patent dynamically adjusts the reference current distribution by generating control signals based on real-time detection of voltage variations in multiple paths. This dynamic compensation mechanism adapts to changing conditions such as temperature fluctuations and power supply variations, maintaining frequency stability while keeping the oscillator integrated on a semiconductor chip.
Solution Approach 2:
The patent changes the distribution parameters of reference currents across multiple paths based on detected variations. By adjusting current magnitudes and distributions in response to process, temperature, and voltage changes, the system maintains frequency stability without requiring external components.
3Ease of manufacture
If multiple reference currents are generated by copying a single reference current through a current mirror circuit, then the oscillator can be integrated on a semiconductor chip, but frequency stability accuracy deteriorates due to mirror ratio variations
Solution Approach 1:
The patent segments the reference current distribution into multiple independent paths with separate control mechanisms. This segmentation eliminates the dependency on current mirror circuit ratios, as each path can be independently adjusted to compensate for variations, thereby improving frequency accuracy while maintaining integrability.
Solution Approach 2:
The patent introduces detection voltages and control signals as intermediaries between the reference current source and the oscillation circuits. These intermediaries enable precise measurement and adjustment of current distribution, compensating for mirror ratio variations and improving frequency accuracy without requiring external components.
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 design stabilizes the clock frequency by ensuring equal reference currents and reduces power consumption, achieving high frequency accuracy and stability while minimizing system offset.
Implementation Method 1
an F/V conversion circuit including a capacitor connected to the first path and structured to charge or discharge the capacitor with the reference current and generate a detection voltage
Implementation Method 2
a path selector structured to distribute the reference current to a first path and a second path in a time-sharing manner in synchronization with the clock
Implementation Method 3
a feedback circuit structured to adjust a control signal so that the detection voltage approaches the reference voltage
Data Source
AI summary
A frequency variable oscillator generates a clock having a frequency according to a control signal. A reference current source generates a reference current. A path selector distributes the reference current to a first path and a second path in a time-sharing manner in synchronization with the clock. An F/V conversion circuit includes a capacitor connected to the first path, and charges or discharges the capacitor with the reference current and generates a detection voltage. The reference voltage source includes a resistor connected to the second path, and outputs a reference voltage according to a voltage across the resistor. A feedback circuit adjusts a control signal so that the detection voltage approaches the reference voltage.