Multiplexed Sensor Digitizer for Low-Noise MEMS Linearity
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Solution Overview
Problem
Existing multi-channel sensor processing technologies face challenges in achieving optimal performance and cost-effectiveness, particularly in designing shared hardware that effectively limits out-of-band signals and noise while maintaining high linearity for MEMS sensors.
Innovation Solution
A sensor output digitizer comprising a multiplexer stage, a multi-stage analog to digital converter, and a digital output combiner, which employs a round-robin selection sequence and a combination of sigma delta and successive approximation register ADCs to sequentially select and digitize sensor outputs, thereby minimizing noise folding and achieving high linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate hardware is allocated for each sensing channel, then measurement precision and reliability are improved, but device complexity and cost increase
Solution Approach 1:
The patent merges multiple sensing channels into a single shared hardware path by time-multiplexing the sensor outputs. The multiplexer combines N sensor channels onto one shared amplifier and ADC, reducing hardware complexity while maintaining measurement precision through proper timing and signal isolation for each channel.
Solution Approach 2:
The patent implements periodic sampling of each sensor channel in a round-robin sequence. Each channel is sampled at regular intervals within a repeating cycle, allowing shared hardware to process multiple channels periodically while maintaining adequate measurement precision for each individual channel.
2Device complexity
If shared hardware is used across multiple sensing channels, then device complexity and cost are reduced, but noise filtering performance deteriorates due to out-of-band signals
Solution Approach 1:
The patent applies preliminary band-limiting filtering to each sensor output before it enters the shared amplifier and ADC. By pre-filtering each channel's bandwidth according to its specific requirements before multiplexing, the system prevents out-of-band noise from contaminating the shared hardware path while maintaining cost-effective shared architecture.
Solution Approach 2:
The patent applies different bandwidth filtering characteristics to different sensor channels based on their specific requirements. Each channel receives tailored band-limiting filtering appropriate to its measurement needs before entering the shared hardware, ensuring optimal noise filtering performance for each local channel while using shared resources.
3Device complexity
If shared hardware is used across multiple sensing channels, then device complexity and cost are reduced, but measurement precision deteriorates due to non-linearity in amplification and conversion
Solution Approach 1:
The patent uses an oversampling ratio greater than 1 in the sigma-delta ADC, where the sampling frequency exceeds the minimum Nyquist requirement. This excessive sampling action enables digital filtering to achieve high effective resolution and linearity in the shared ADC, compensating for the shared hardware architecture and maintaining measurement precision across all channels.
Data Source
AI summary
The described technology is generally directed towards a sensor output digitizer. The sensor output digitizer can comprise a multiplexer stage, a multi-stage analog to digital converter, and a digital output combiner. The multiplexer stage can be configured to sequentially select sensor outputs from one or more sensors, resulting in a stream of selected sensor outputs. The multi-stage analog to digital converter can be coupled with the multiplexer stage, and can be configured to convert the stream of selected sensor outputs into a stream of digitized outputs. The digital output combiner can be configured to re-scale and sum intermediate outputs of the multi-stage analog to digital converter to produce a stream of digitized sensor outputs.