Noise-Shaping Switched-Capacitor Comparator for Offset Error Control
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Solution Overview
Problem
Comparator based switch capacitor circuits suffer from errors due to circuit delay and comparator offset, which degrade system performance and introduce low-frequency noise, such as flicker noise.
Innovation Solution
The implementation of a noise shaping comparator based switch capacitor circuit that spectrally modulates circuit-induced noise by using a logical signal to control the polarity of connections for capacitors, effectively toggling the SWAP signal to convert errors into high-frequency noise irrelevant in over-sampling systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional comparator based switch capacitor circuit is used, then circuit simplicity is maintained, but circuit-induced errors and low-frequency noise degrade system performance
Solution Approach 1:
The patent applies noise shaping to convert the harmful low-frequency circuit-induced noise into high-frequency noise. By using a modulating signal to dynamically adjust the capacitor connections during sampling and transfer phases, the circuit transforms the unavoidable comparator offset and delay errors into high-frequency components that can be filtered out in over-sampling systems, thereby converting a harmful effect into a beneficial one.
2Object-generated harmful factors
If noise shaping with logical signal control is implemented, then circuit-induced noise is converted to high-frequency components, but device complexity increases
Solution Approach 1:
The patent introduces dynamic control through a logical signal that changes the polarity of capacitor connections based on the current phase (sampling or transfer). This dynamic switching mechanism allows the same physical capacitors to serve different functions at different times, enabling noise shaping without adding substantial hardware complexity. The dynamic reconfiguration of existing components achieves the noise conversion function.
Solution Approach 2:
The noise shaping mechanism operates periodically by alternating between sampling phase and transfer phase, controlled by non-overlapping clock signals. During each period, the logical signal toggles to change capacitor connections appropriately. This periodic action allows the circuit to systematically convert low-frequency noise to high-frequency noise through regular phase transitions, achieving noise shaping through time-domain multiplexing.
Data Source
AI summary
A noise shaping comparator based switch capacitor (CBSC) comprises a comparator, a charge pump, a plurality of capacitors, and a plurality of shufflers. Each shuffler is controlled by a logical signal to determine a polarity of connection for a circuit element within the CBSC circuit. The CBSC circuit operates cyclically through a sampling phase and a transfer phase. During the sampling phase, the CBSC circuit samples an input voltage; during the transfer phase, the CBSC circuit amplifies the sampled input voltage by a ratio and transfers a first resultant voltage to a load using the charge pump circuit. A noise induced by the CBSC circuit due to circuit non-idealities is thus modulated by the logical signal. The noise is therefore spectrally shaped into having a spectral characteristics determined by the logical signal.