Capacitor Rotation in ADCs to Shift Mismatch Tones
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Solution Overview
Problem
Analog-to-digital converters face challenges in achieving high resolution and reducing the influence of capacitance value tolerances in capacitor arrays, leading to mismatches that result in tones at undesirable frequencies, which can fall within the band of interest, affecting measurement accuracy.
Innovation Solution
The implementation of a rotation frequency control unit that dynamically changes the position of capacitor elements within the capacitor array based on a rotation signal with varying frequencies, ensuring that mismatches are set outside the band of interest by adjusting the rotation frequency in accordance with the gain setting, thereby improving resolution and reducing tone interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitor elements are used in the capacitor array, then the analog-to-digital converter can perform conversion operations, but capacitance value tolerances cause mismatches that result in tones at undesirable frequencies within the band of interest
Solution Approach 1:
The patent applies dynamic element rotation by making the capacitor elements movable between different positions in the capacitor array. The rotation signal dynamically changes which capacitor elements are connected to which nodes, transforming a static capacitor array into a dynamic one. This dynamic repositioning ensures that mismatch tones are rotated out of the band of interest while maintaining conversion accuracy.
Solution Approach 2:
The patent implements periodic rotation of capacitor elements using a rotation signal with a specific rotation frequency. The capacitor elements are rotated periodically through multiple positions, and the rotation frequency is carefully selected to be outside the band of interest. This periodic action converts the harmful mismatch tones to frequencies that do not interfere with the measurement band.
2Object-generated harmful factors
If the position of capacitor elements is changed dynamically, then tone frequencies are moved outside the band of interest, but the device complexity increases due to the rotation frequency control unit and rotation signal generation
Solution Approach 1:
The patent makes the capacitor array multi-functional by enabling it to serve both as the conversion capacitor array and as a dynamically reconfigurable structure. The same capacitor elements are reused in different positions rather than requiring separate capacitor sets for different functions, reducing overall device complexity despite the added rotation control.
Solution Approach 2:
The patent changes the operational parameters of the capacitor array by introducing a rotation frequency parameter that controls the dynamic repositioning. By adjusting the rotation frequency to be outside the band of interest, the system manages tone interference through parameter optimization rather than through complex structural modifications.
3Measurement precision
If high resolution is achieved through high precision capacitors, then measurement accuracy improves, but manufacturing precision requirements and cost increase due to tight capacitance tolerance specifications
Solution Approach 1:
The patent converts the harmful effect of capacitance mismatch into a beneficial one by rotating the mismatch tones out of the band of interest. Instead of requiring tight capacitance tolerances to avoid mismatch effects, the system accepts standard tolerance capacitors and uses dynamic rotation to move the resulting tones to harmless frequencies, thereby achieving high resolution without stringent manufacturing precision requirements.
Data Source
AI summary
An analog-to-digital converter comprises a first integrator (40), a first converter input (19), a first reference voltage input (34), a capacitor array (68) comprising capacitor elements (171), and a rotation frequency control unit (37) providing a rotation signal (SRO) with at least two different values of a rotation frequency (fR). A first subset of capacitor elements (171) of the capacitor array (68) is coupled to the first converter input (19) and to an input side of the first integrator (40) in a first phase and is coupled to the first reference voltage input (34) and to the input side of the first integrator (40) in a second phase as a function of the rotation signal (SRO).