Programmable Voltage-to-Time Converter With Injection-Locked Gain Tuning
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Solution Overview
Problem
Current voltage to time converters (VTCs) have limited gain control capabilities, often requiring preamplifier stages or automatic gain control, which increase complexity and power consumption, and struggle with distortion and voltage headroom limitations.
Innovation Solution
A programmable voltage to time converter with a capacitive injection locked oscillator structure, featuring a relaxation oscillator with a linearly controllable component, allowing for independent and precise gain and bandwidth control without additional components, using a gain control word to adjust the system's gain and bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a preamplifier stage or automatic gain control is added to improve signal conditioning and gain control, then the gain control capability is improved, but the device complexity and power consumption increase
Solution Approach 1:
The patent combines the gain control function directly into the VTC core architecture by making the injection current programmable, merging what would traditionally be separate blocks (VTC + preamplifier/AGC) into a single integrated unit. This eliminates the need for additional signal conditioning stages while maintaining full gain control capability.
Solution Approach 2:
The programmable injection current source serves multiple functions: it provides the oscillation current for the relaxation oscillator, enables gain control through current magnitude adjustment, and allows bandwidth control through the same current programming mechanism. This multi-functionality eliminates the need for dedicated preamplifier or AGC circuits.
2Adaptability or versatility
If a preamplifier stage or automatic gain control is added to improve signal conditioning and gain control, then the gain control capability is improved, but the power consumption increases
Solution Approach 1:
The patent combines the gain control function directly into the VTC core architecture by making the injection current programmable, merging what would traditionally be separate blocks (VTC + preamplifier/AGC) into a single integrated unit. This eliminates the need for additional signal conditioning stages while maintaining full gain control capability.
Solution Approach 2:
The programmable injection current source serves multiple functions: it provides the oscillation current for the relaxation oscillator, enables gain control through current magnitude adjustment, and allows bandwidth control through the same current programming mechanism. This multi-functionality eliminates the need for dedicated preamplifier or AGC circuits.
3Adaptability or versatility
If variable slope VTC architecture is used to provide gain control through injection current, then the gain tuning is improved, but the output swing distortion increases around the limits
Solution Approach 1:
The patent employs a relaxation oscillator architecture where the oscillation frequency is dynamically adjusted by the input voltage modulating the discharge timing of a capacitor. This dynamic operation allows the output to swing between rail-to-rail limits without the distortion issues of variable slope architectures, as the oscillation mechanism naturally accommodates full voltage excursions.
Solution Approach 2:
The patent changes the operating parameter from current modulation (variable slope) to voltage-modulated timing (relaxation oscillator). By using the input voltage to control the charging/discharging timing of a capacitor rather than modulating a current, the system achieves both gain control and maintains output swing linearity across the full voltage range.
4Adaptability or versatility
If constant-slope VTC architecture is used with multiple degrees of freedom for gain control, then the gain control flexibility is improved, but the tuning difficulty increases
Solution Approach 1:
The patent uses a relaxation oscillator where the oscillation frequency is determined by a single dominant time constant formed by a capacitor and the discharge current. By programming the discharge current magnitude, the gain is directly controlled without the need to coordinate multiple parameters, simplifying the tuning process while maintaining flexibility.
Solution Approach 2:
The patent segments the gain control into discrete programmable current levels that directly map to frequency output levels. This segmentation allows for easy digital control of the injection current, where each digital code corresponds to a specific current magnitude and thus a specific gain setting, making tuning straightforward and predictable.
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 accurate and easy gain control, reducing complexity and power consumption, while maintaining low distortion and rail-to-rail conversion, and is compatible with various sensors, suitable for low-power applications like biomedical and IoT devices.
Implementation Method 1
This is achieved using a relaxation oscillator having a capacitive injection locked oscillator structure, called C-ILO
Data Source
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AI summary
The invention concerns a programmable voltage to time converter (10), comprising: - a locking frequency generator (12) configured to generate a locking frequency; - a current generator (14) configured to generate a biasing current; - a relaxation oscillator (18) configured to be powered by the biasing current and to generate an output voltage signal from the locking frequency, a gain control word and an input voltage signal; - a phase difference block (20) configured to determine a phase difference between a first signal corresponding to the output voltage signal and a second signal determined based on the locking frequency. The relaxation oscillator (18) comprises a component presenting a linearly controllable characteristic. The voltage to time converter (10) presents a gain linearly or dB-linearly controllable based on the gain control word by controlling linearly said characteristic of said component.