Differential VCO ADC for Full-Range Voltage Measurement
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Solution Overview
Problem
Existing analog-to-digital conversion methods, such as micro Sigma-Delta ADCs, are bulky and struggle to maintain speed and accuracy across the full voltage range due to limitations in oscillator design, particularly for ring oscillators which can only cover about ¾ of the voltage range and slow down near the voltage edges.
Innovation Solution
The use of differential oscillator techniques with two voltage-controlled oscillators, one NMOS-based and one PMOS-based, each covering half of the input voltage range, allowing for accurate measurement across the full range by utilizing the difference in their output frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a single ring oscillator is used for analog-to-digital conversion, then the device size is reduced, but the voltage range coverage is limited to about ¾ of the full range and speed decreases near voltage edges
Solution Approach 1:
The patent divides the voltage range coverage task into two segments by using separate NMOS-based and PMOS-based oscillators. Each oscillator type covers a specific portion of the voltage range where it operates most effectively, with the NMOS oscillator covering the lower range and the PMOS oscillator covering the upper range, thereby achieving full voltage range coverage while maintaining small device size.
2Device complexity
If a single ring oscillator is used, then device complexity is reduced, but measurement accuracy deteriorates across the full voltage range
Solution Approach 1:
The patent applies local quality by using different oscillator types (NMOS and PMOS) optimized for different regions of the voltage range. Each oscillator type has tailored characteristics that make it particularly accurate in its designated operating region, ensuring high measurement precision across the entire voltage range while keeping the overall device complexity manageable.
3Adaptability or versatility
If traditional ADCs are used, then full voltage range coverage is achieved, but the device size becomes bulky
Solution Approach 1:
The patent merges the functionality of multiple oscillators into a unified differential oscillator system. By combining an NMOS-based oscillator and a PMOS-based oscillator in a differential configuration, the system achieves full voltage range coverage comparable to traditional ADCs while occupying significantly less silicon area due to the efficient use of complementary transistor structures.
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 approach maintains speed and accuracy across the entire voltage range, is significantly smaller than traditional ADCs, and reduces measurement errors, with errors close to zero across most of the measurement range, peaking at 3 mV.
Implementation Method 1
detecting, at a common input of a first voltage-controlled oscillator (VCO) and a second VCO, an input voltage signal; determining a voltage level of the input voltage signal; and activating one or both of the first VCO and the second VCO based on the voltage level
Data Source
AI summary
An apparatus includes a pair of voltage-controlled oscillators (VCOs). The pair includes a first VCO with a first biasing stage receiving an input voltage signal and a first output stage coupled to the first biasing stage. The first output stage generates a first output frequency signal based on the input voltage signal. The pair also includes a second VCO. The second VCO includes a second biasing stage receiving the input voltage signal and a second output stage coupled to the second biasing stage. The second output stage generates a second output frequency signal based on the input voltage signal.