Segmented Voltage-Signal Circuit for Linear Low-Area ADCs
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Solution Overview
Problem
Existing CDAC-based SAR ADC circuitry faces an area penalty as resolution increases, and segmentation to reduce area leads to non-linearity issues.
Innovation Solution
The controllable voltage-signal generation circuitry uses a series of segment nodes connected by coupling capacitors with switches that can connect to different reference voltage sources, allowing for precise control of voltage changes to compensate for parasitic capacitances and relax capacitor value restrictions, thereby reducing area and improving linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If segmentation is used to reduce area, then area is reduced, but non-linearity issues arise
Solution Approach 1:
The circuit is divided into multiple segments where each segment contains capacitors connected to different reference voltage sources. This segmentation allows independent control of voltage changes in each segment, enabling area reduction while maintaining linearity through compensated design.
Solution Approach 2:
The invention changes the voltage parameters by connecting capacitors to multiple reference voltage sources with different voltage levels. By controlling switches to connect capacitors to different reference voltages, the circuit achieves precise voltage signal generation that compensates for parasitic effects and maintains linearity.
2Measurement precision
If more capacitors are used to improve resolution, then resolution is improved, but area increases
Solution Approach 1:
Each capacitor in the segmented circuit serves multiple functions: it contributes to resolution through its capacitance value, enables voltage control through switch connections to different reference sources, and participates in linearity compensation through coordinated switching. This multi-functionality allows achieving high resolution without proportionally increasing area.
Solution Approach 2:
The circuit uses dynamic switching to connect capacitors to different reference voltage sources based on the desired output voltage signal. This dynamic control allows the same physical capacitors to generate multiple voltage levels, achieving high resolution through temporal multiplexing rather than requiring all capacitors to be permanently connected.
3Device complexity
If traditional CDAC architecture is used, then simplicity is maintained, but parasitic capacitances cause non-linearity
Solution Approach 1:
The invention converts the harmful effect of parasitic capacitances into a beneficial control mechanism. By using multiple reference voltage sources and controlled switching, the circuit compensates for parasitic capacitance effects, transforming what would be a source of error into a means for achieving higher precision through differential voltage control.
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 control of output voltage signals with fewer and smaller capacitors, reduces area requirements, and mitigates non-linearity errors caused by parasitic capacitances, enhancing the signal-to-noise ratio and effective number of bits in ADC applications.
Implementation Method 1
a plurality of segment nodes connected together in series, each adjacent pair of segment nodes in the series connection being connected together via a corresponding coupling capacitor
Data Source
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AI summary
Controllable voltage-signal generation circuitry, comprising: a plurality of segment nodes connected together in series, each adjacent pair of segment nodes in the series connection being connected together via a corresponding coupling capacitor, an end one of the segment nodes in the series connection serving as an output node; for each of the segment nodes, at least one segment capacitor having first and second terminals, the first terminal connected to that segment node and the second terminal connected to a corresponding switch; and switch control circuitry, wherein: each switch is operable to connect the second terminal of its segment capacitor to one reference voltage source and then instead to another reference voltage source, those reference voltage sources having different voltage levels, to apply a voltage change at the second terminal of its segment capacitor; the reference voltage sources and switches are configured such that for each segment node the same voltage change in magnitude is applied by each switch of that segment node, and such that the voltage change applied by each switch of one segment node is different in magnitude from the voltage change applied by each switch of another segment node; and the switch control circuitry is configured to control the switches so as to control a voltage signal at said output node.