Charge-Injection ADC Circuit for Better Linearity in Small Area
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Solution Overview
Problem
Existing digital slope analog to digital converters face poor linearity due to capacitor mismatches and require a large number of capacitors, leading to increased circuit area and device cost.
Innovation Solution
A digital slope analog to digital converter using a charge injection digital to analog converter circuit with a single current source to adjust charges in two capacitors, sampling input signals and generating decision signals to detect a crossing point, thereby reducing the impact of capacitor mismatches and circuit area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitor array circuit with multiple capacitors is employed to generate ramp voltage change, then the analog to digital converter can perform signal conversion, but capacitor mismatches cause poor linearity
Solution Approach 1:
The patent merges the functions of multiple capacitors into a single capacitor by using a charge injection circuit that sequentially adds or removes charge packets. This single capacitor approach eliminates mismatch issues while maintaining the ramp voltage generation capability through controlled charge injection rather than relying on multiple precise capacitors working together.
Solution Approach 2:
The patent changes the operating parameter from voltage-based ramp generation (requiring multiple capacitors) to charge-based ramp generation. By injecting discrete charge packets into a single capacitor, the system achieves precise voltage changes without the mismatch problems inherent in multi-capacitor arrays, thereby improving linearity.
2Measurement precision
If a sufficient number of capacitors is required to produce the ramp voltage change, then the analog to digital converter can achieve adequate resolution, but the circuit area and device cost are increased significantly
Solution Approach 1:
The patent consolidates multiple capacitor functions into a single capacitor using charge injection technology. This single capacitor can achieve the same resolution as multiple capacitors by sequentially injecting charge packets, dramatically reducing the circuit area while maintaining conversion precision.
Solution Approach 2:
The patent replaces the physical multi-capacitor array structure with a charge injection control system. Instead of using multiple physical capacitors to achieve resolution, the system uses a single capacitor controlled by digital-to-analog charge injection, reducing hardware complexity and area while maintaining precision.
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 improves linearity and reduces circuit area by using a single current source to adjust charges in capacitors, effectively addressing the limitations of existing converters.
Implementation Method 1
a first capacitor and a second capacitor are respectively configured to sample a first input signal and a second input signal, and generate a first signal and a second signal
Implementation Method 2
a charge injection digital to analog converter circuit is configured to gradually adjust charges stored in at least one of the first capacitor or the second capacitor
Data Source
AI summary
A digital slope analog to digital converter includes a charge injection digital to analog converter (DAC) circuit, a comparator circuit, a detector circuit, and a control logic circuitry. The charge injection DAC circuit respectively samples input signals via first and second capacitors and generates a first signal via the first capacitor and a second signal via the second capacitor. The comparator circuit compares the first signal with the second signal to generate decision signals. The detector circuit generates a flag signal according to the decision signals. The control logic circuitry generates an enable signal according to the flag signal and generates a digital output when the comparator circuit detects a crossing point of the first and second signals. The charge injection DAC circuit gradually adjusts charges stored in the first and/or the second capacitor according to the enable signal until the crossing point is detected.