Switched-Capacitor Single-to-Differential Conversion for Higher SNR
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Solution Overview
Problem
Single-ended signals are susceptible to noise and have limited signal swing, which hampers the performance of electronic components, and existing conversion methods are inadequate in effectively converting them into differential signals to improve performance.
Innovation Solution
A single-ended to differential-ended converter circuit utilizing sampling capacitors and switch groups to convert single-ended signals into differential signals, enhancing signal swing and noise immunity by outputting differential signals at two nodes, with specific control of switches and capacitors during sampling and hold phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If single-ended signals are used, then the circuit structure is simple, but the signal swing is limited and noise susceptibility increases
Solution Approach 1:
The patent segments the single-ended signal into two separate differential signals by using two sampling capacitors (first and second sampling capacitors) that independently process different aspects of the input signal. This segmentation allows the output to be split into two complementary signals at different output nodes, effectively converting a single-ended signal into a differential signal pair, thereby improving noise immunity while maintaining reasonable circuit complexity
Solution Approach 2:
The patent transitions from a single-dimensional single-ended signal to a two-dimensional differential signal structure by introducing a reference voltage dimension. The first sampling capacitor connects the output node to the reference voltage, while the second sampling capacitor connects another output node to ground or a different reference, creating a differential voltage relationship that adds a dimensional aspect to the signal representation
2Device complexity
If single-ended signals are used, then the circuit structure is simple, but the signal swing is only half of differential signals
Solution Approach 1:
The patent segments the signal processing into two parallel paths using two sampling capacitors, where each capacitor processes the signal independently to generate one component of the differential output. This segmentation enables the full signal swing to be distributed across both output nodes in a differential manner, effectively doubling the usable signal swing compared to a single-ended output
Solution Approach 2:
The patent merges the functionality of signal sampling and reference voltage application into a unified differential conversion structure. By combining the first sampling capacitor with reference voltage connection and the second sampling capacitor with ground/different reference connection, the circuit achieves differential signal generation that provides full signal swing while maintaining a relatively simple overall structure
3Object-affected harmful factors
If sampling capacitors and switch groups are used for conversion, then the signal-to-noise ratio is improved, but the device complexity increases
Solution Approach 1:
The sampling capacitors and switch groups serve multiple functions simultaneously: they perform signal sampling during the sampling phase, hold the sampled voltage during the hold phase, and contribute to differential voltage generation at the output. This multi-functionality reduces the need for separate dedicated components for each function, thereby improving signal-to-noise ratio while limiting the increase in overall device complexity
Solution Approach 2:
The patent employs periodic switching action where the switch group alternates between connecting the sampling capacitors to the input signal (sampling phase) and isolating them (hold phase). This periodic action, synchronized with the input signal timing, enables effective signal capture and noise rejection while using a relatively simple switched-capacitor architecture rather than more complex continuous-time circuits
Data Source
AI summary
A method of converting a single-ended signal to a differential-ended signal includes the following steps: providing a first sampling capacitor having a first end and a second end; providing a second sampling capacitor having a third end and a fourth end; at a first time point, controlling the first end to receive a single-ended signal, controlling the second end to receive a reference voltage, controlling the third end to receive the reference voltage or a middle voltage value of the swing of the single-ended signal, and controlling the fourth end to receive the single-ended signal; and at a second time point, controlling the second end and the fourth end to receive the reference voltage. The first end and the third end output a differential signal after the second time point which is later than the first time point.