External Resistor Oscillator Circuit for Accurate Frequency Control
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Solution Overview
Problem
Oscillators with on-chip resistor components face challenges in achieving frequency accuracy within 1% of a target frequency due to temperature-dependent non-linear variations and drift over time. Additionally, external resistors connected to oscillator chips are prone to noise, causing frequency errors and jitter.
Innovation Solution
The system incorporates an oscillator circuit on a chip with a charging current generator and oscillator circuitry. This includes a current mirror, amplifier, on-chip resistor, external resistor, and capacitor. The on-chip resistor is coupled to an external resistor and capacitor to enhance accuracy and stability, while additional internal resistors are added to compensate for variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an on-chip resistor is used in the oscillator circuit, then the oscillator can be integrated on a single chip, but the frequency accuracy deteriorates due to temperature-dependent non-linear variations and drift over time
Solution Approach 1:
The patent introduces an external resistor as an intermediary component that replaces the problematic on-chip resistor for frequency-determining functions. This external resistor serves as a mediator between the oscillator circuit and the frequency accuracy requirement, eliminating temperature-dependent drift while maintaining circuit integration benefits. The external resistor is connected to the oscillator chip through a dedicated pin, allowing it to function as the primary frequency-determining element without being subject to on-chip temperature variations.
2Measurement precision
If an external resistor is connected to the oscillator chip, then frequency accuracy improves, but noise susceptibility increases causing frequency errors and jitter
Solution Approach 1:
The patent applies local quality by creating a dedicated noise-isolated pathway for the external resistor connection. A specific pin on the oscillator chip is designated solely for the external resistor connection, electrically isolating the frequency-determining resistor from other noisy on-chip circuits. This localized quality control ensures that the external resistor experiences minimal electromagnetic interference and noise coupling, thereby reducing frequency jitter and errors while maintaining accuracy.
3Stability of the object's composition
If additional internal resistors are added to compensate for variations, then frequency stability improves, but device complexity increases
Solution Approach 1:
The patent extracts the frequency-determining resistor function from the on-chip circuitry and places it externally. By taking out the resistor that causes temperature-dependent variations and drift, the patent eliminates the need for complex compensation circuits with multiple internal resistors. The external resistor assumption simplifies the overall device complexity while maintaining frequency stability, as the external component is less susceptible to on-chip temperature variations and drift.
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
The solution provides increased accuracy and stability of the oscillator frequency by compensating for internal resistor variations and reducing noise-induced errors, thereby achieving frequency accuracy within 1% of the target frequency.
Implementation Method 1
a charging current generator including a current mirror, an amplifier, and an on-chip resistor
Implementation Method 2
the on-chip resistor is coupled to the amplifier and to a pin on the chip
Data Source
AI summary
In an example, a system includes an oscillator circuit on a chip. The oscillator circuit includes a charging current generator including a current mirror, an amplifier, and an on-chip resistor, where the on-chip resistor is coupled to a pin on the chip. The oscillator circuit also includes oscillator circuitry coupled to the charging current generator, where the oscillator circuitry includes a comparator, a phase generator, a first capacitor coupled to a first resistor, and a second capacitor coupled to a second resistor. The system also includes an external resistor coupled to the pin, where the external resistor is external to the chip. The system includes an external capacitor coupled to the pin, where the external capacitor is external to the chip.