Pseudo-Differential Switched-Capacitor Circuit With Common-Mode Stabilization
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Solution Overview
Problem
Pseudo-differential switched-capacitor circuits face challenges in handling high-frequency input common mode voltage disturbances and charge injection effects, which affect the stability of the output common-mode level.
Innovation Solution
The implementation of a differential floating sampling (DFS) circuit with an integrator-based common-mode stabilization technique, where the integrator samples common-mode voltage disturbances and feeds back the integrator output to the single-ended amplifiers during the sampling phase to stabilize the output common-mode level and reduce charge injection errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a pseudo-differential amplifier is used to enlarge output signal range for low voltage design, then the output signal range is improved, but the common-mode noise immunity deteriorates
Solution Approach 1:
The patent implements common-mode feedback circuits that sense the common-mode voltage at the outputs and generate corrective signals to counteract common-mode disturbances. This feedback mechanism actively stabilizes the common-mode level while preserving the enlarged output signal range achieved through pseudo-differential architecture
Solution Approach 2:
The patent separates the differential signal path from the common-mode control path. The pseudo-differential amplifier handles the main signal amplification with enlarged swing, while dedicated common-mode feedback circuits independently manage common-mode noise rejection, allowing both functions to operate optimally
2Object-generated harmful factors
If an integrator-based feedback mechanism is used to cancel charge injection effect, then the charge injection effect is reduced, but the response to high-frequency common mode voltage disturbance deteriorates
Solution Approach 1:
The patent employs dynamic common-mode feedback that adapts its response characteristics. The feedback circuit uses capacitive coupling and switching mechanisms that provide strong correction for high-frequency disturbances while maintaining charge injection cancellation, allowing the system to respond dynamically to different types of common-mode errors
Solution Approach 2:
The patent introduces intermediate capacitive coupling elements in the common-mode feedback path that allow high-frequency signals to pass through effectively while blocking DC charge injection effects. These intermediary components enable frequency-selective common-mode correction
3Stability of the object's composition
If the integrator samples common-mode voltage and feeds back during sampling phase, then the output common-mode level is stabilized, but the circuit complexity increases
Solution Approach 1:
The patent combines the common-mode sampling function with the existing differential floating sampling circuitry. The same switching network and capacitors used for differential signal sampling are also utilized for common-mode voltage sampling, eliminating the need for separate dedicated sampling components
Solution Approach 2:
The integrator circuit serves multiple functions: it integrates the common-mode feedback signal, samples the common-mode voltage during the sampling phase, and provides correction during the amplification phase. This multi-functionality reduces the need for separate circuits for each function
Data Source
AI summary
A pseudo-differential switched-capacitor circuit, which can be applied to various signal processing circuits, employs a floating sampling technique and an integrator feedback loop for isolating a common mode voltage disturbance and restraining a charge injection effect. The pseudo-differential switched-capacitor circuit includes a differential floating sampling circuit that has a pseudo-differential architecture, and an integrator for reducing the charge injection effect within the differential floating sampling circuit.