Differential Delta-Sigma Modulator With Low-Power Common-Mode Feedback
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Solution Overview
Problem
Hearing aids require noise-immune and power-efficient signal processing, which is challenging for differential topologies due to higher power consumption compared to single-ended amplifiers, especially in integrated circuits with increasing functionalities.
Innovation Solution
A differential delta-sigma modulator using a pair of single-ended amplifiers, which reduces power consumption while maintaining noise immunity by employing a pair of single-ended amplifiers in the integrator stage and utilizing switchable capacitors for common mode feedback, ensuring low power operation and noise rejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If differential topologies are used for noise immunity, then noise immunity is improved, but power consumption increases
Solution Approach 1:
The integrator is segmented into two separate single-ended amplifiers (first and second single-ended amplifiers) that operate in a differential configuration. Each amplifier processes one polarity of the differential signal independently, allowing the system to achieve differential noise rejection while using simpler, lower-power single-ended amplifier stages rather than a single complex differential amplifier
Solution Approach 2:
Instead of using traditional differential amplifiers to achieve noise immunity, the invention inverts the approach by using single-ended amplifiers in a differential configuration. The first single-ended amplifier processes the non-inverted input signal while the second processes the inverted input signal, achieving differential noise rejection through the inverted architecture rather than through traditional differential amplification
2Use of energy by moving object
If single-ended amplifiers are used to reduce power consumption, then power consumption is reduced, but noise immunity deteriorates
Solution Approach 1:
The invention merges two single-ended amplifiers into a unified differential integrator structure. By combining the outputs of the first and second single-ended amplifiers in a differential configuration, the system achieves the noise immunity of differential topologies while retaining the power efficiency of single-ended amplifier stages
Solution Approach 2:
The invention implements feedback mechanisms where the output of each single-ended amplifier is fed back to its respective input through feedback capacitors. This feedback stabilizes the operation of the single-ended amplifiers and enables them to achieve differential signal processing performance, effectively compensating for the lack of inherent differential structure while maintaining low power consumption
Data Source
AI summary
A differential delta-sigma-modulator has an integrator including a pair of single-ended amplifiers. A sample clock is driving a first switchable capacitor configuration and a second switchable capacitor configuration at a predetermined switching cycle. The first switchable capacitor configuration is adapted for sampling respective outputs from the pair of single-ended amplifiers on a pair of output sampling capacitors in the first part of the switching cycle. The second switchable capacitor configuration is adapted for charging a common mode capacitor with the average voltage of the voltage sampled by the pair of output sampling capacitors in the second part of the switching cycle. The voltage across the common mode capacitor represents the common mode voltage for the integrator.