Threshold-Compensated Oscillator for Stable Low-Voltage Frequency
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Solution Overview
Problem
Oscillators used in semiconductor memories face challenges in maintaining stable oscillating frequency and low voltage drive, particularly in applications requiring a wide range of power supply voltages, such as mobile telephones and camera modules.
Innovation Solution
The oscillator incorporates a constant current circuit that generates a current varying with the on threshold voltage of a transistor, and an oscillating circuit where the oscillating frequency of the clock signal varies positively with the constant current supplied, while negatively with the on threshold voltage of the transistor, ensuring a stable frequency across varying power supply voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional oscillators are used in semiconductor memories, then they can operate over a wide range of power supply voltages, but the oscillating frequency becomes unstable
Solution Approach 1:
The patent changes the parameters of the constant current circuit and oscillating circuit to create a compensation mechanism. The constant current circuit is designed so that its current varies positively with transistor threshold voltage, while the oscillating circuit is designed so that its frequency varies negatively with threshold voltage. This parameter configuration enables the frequency variations to cancel each other out, maintaining stable oscillation over wide voltage ranges.
Solution Approach 2:
The patent implements a feedback mechanism where the constant current circuit continuously adjusts the current supplied to the oscillating circuit based on transistor threshold voltage variations. This feedback loop compensates for frequency drift caused by voltage changes, ensuring stable oscillating frequency across different power supply conditions.
2Use of energy by moving object
If oscillators are designed for low voltage drive (1.7V), then they can meet mobile device requirements, but maintaining proper oscillating frequency characteristic becomes difficult
Solution Approach 1:
The patent optimizes the parameters of the constant current circuit and oscillating circuit specifically for low voltage operation. By carefully selecting component values and circuit topology, the system achieves reliable oscillation at 1.7V while maintaining frequency characteristics through the threshold voltage compensation mechanism.
Solution Approach 2:
The oscillator circuit is designed to self-regulate its operation at low voltages. The constant current circuit automatically adjusts the bias current based on the actual transistor threshold voltage, which varies with manufacturing process and temperature, enabling the circuit to maintain stable frequency without external calibration or adjustment.
Data Source
AI summary
An oscillator of the present invention includes a constant current circuit in which a constant current generated in the constant current circuit varies positively with an on threshold voltage of a transistor included in the constant circuit; and an oscillating circuit in which the oscillating frequency of a clock signal generated in the oscillating circuit varies positively with the constant current supplied from the constant current circuit, and the oscillating frequency of the clock signal generated in the oscillating circuit varies negatively with an on threshold voltage of a transistor included in the oscillating circuit.