Clock Oscillator Circuit With Switched Capacitance Frequency Stabilization
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Solution Overview
Problem
Conventional clock generating circuits in semiconductor integrated circuit devices face challenges in maintaining high frequency accuracy due to temperature and power supply variations, leading to errors caused by current mismatches, parasitic capacitances, and sub-threshold leakage, which affect the stability of oscillation frequencies.
Innovation Solution
A semiconductor integrated circuit device with a clock oscillating unit comprising a voltage control oscillator, a reference voltage generating circuit, a reference current generating circuit, and a frequency-voltage converting circuit with electrostatic capacitive units and switch units that adjust capacitance and current mirror ratios to stabilize the oscillation frequency, minimizing temperature and power supply dependencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional clock generating circuit is used, then the circuit structure is simple, but the frequency accuracy deteriorates due to temperature and power supply variations
Solution Approach 1:
The patent implements a feedback mechanism where the oscillation frequency is continuously monitored and compared against a reference frequency. The phase detector detects frequency deviations and generates correction signals that are fed back to the voltage-controlled oscillator to adjust its output frequency, thereby maintaining high frequency accuracy despite temperature and power supply variations.
Solution Approach 2:
The patent employs temperature compensation techniques that dynamically adjust circuit parameters based on detected temperature conditions. By changing resistance values, capacitance values, or bias currents in response to temperature variations, the system maintains stable oscillation frequency across different thermal environments without requiring overly complex compensation circuits.
2Stability of the object's composition
If temperature compensation is implemented, then frequency stability improves, but circuit complexity increases
Solution Approach 1:
The patent implements a self-adjusting temperature compensation mechanism where the circuit automatically detects its own temperature conditions and adjusts its parameters accordingly. The temperature sensor monitors the circuit's thermal state and triggers compensation actions within the same circuit, eliminating the need for external complex compensation systems while maintaining frequency stability.
Solution Approach 2:
The patent uses composite circuit structures that combine elements with opposite temperature coefficients. By integrating resistors, capacitors, and active devices with complementary thermal characteristics, the circuit achieves inherent temperature compensation where the temperature drifts of different components cancel each other out, reducing the need for additional compensation circuitry.
3Measurement precision
If current mirror circuits are used, then the circuit design is simplified, but current mismatches cause frequency errors
Solution Approach 1:
The patent divides the current mirror function into multiple independent current sources rather than using a single monolithic current mirror. Each current source is independently controlled and can be individually optimized, allowing for better matching and reduced cumulative errors while maintaining design simplicity through modular construction.
Solution Approach 2:
The patent employs dynamic current adjustment mechanisms that continuously monitor and correct current mismatches in real-time. By making the current sources adaptive rather than static, the system compensates for manufacturing variations and drift over time, achieving high frequency accuracy without requiring extremely precise initial current mirror matching.
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 solution enables the generation of high-precision clock signals by effectively mitigating errors caused by temperature and power supply variations, improving the reliability of semiconductor integrated circuit devices by ensuring stable frequency accuracy across different conditions.
Implementation Method 1
a frequency-voltage converting circuit with electrostatic capacitive units and switch units that adjust capacitance and current mirror ratios
Data Source
AI summary
A frequency-voltage converting circuit 13 is composed of a switch unit including switches SW1 and SW2, electrostatic capacitive elements C and C10 to C13, and switches CSW0 to CSW3. The electrostatic capacitive elements C10 to C13 are composed of elements having mutually different absolute values of capacitance and are provided so as to cover a frequency range intended by a designer. The electrostatic capacitance values are weighted by, for example, 2. The electrostatic capacitive elements C11 to C13 are selected by, for example, the switches CSW0 to CSW3 based on 4-bit frequency adjustment control signals SELC0 to SELC3, thereby carrying out frequency switching.