Shared Anti-Aliasing Filter Switching for Low-Latency Cell Sensing
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Solution Overview
Problem
Conventional circuits for monitoring multiple battery cells require a large area due to multiple anti-aliasing filters, leading to high latency and inefficient die usage, while reducing the number of filters through multiplexing increases latency.
Innovation Solution
The system employs two anti-aliasing filters for a group of four battery cells, where one filter charges while the other provides output to the analog-to-digital converter, using a controller to sequence switch states and reduce latency while minimizing die area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple anti-aliasing filters are used for each battery cell, then measurement precision and reliability are improved, but device area increases significantly
Solution Approach 1:
Multiple anti-aliasing filters are merged into a single shared filter that serves multiple battery cells. The filter is time-multiplexed to process signals from different cells sequentially, reducing the total number of filters from four (one per cell) to one shared filter, thereby significantly reducing die area while maintaining measurement precision through proper timing and buffering.
Solution Approach 2:
A single anti-aliasing filter is designed to perform multiple functions by serving as a shared resource for multiple battery cells. The filter can be dynamically configured to process signals from any of the four battery cells through switch matrix control, making it a universal component that replaces multiple dedicated filters.
2Area of stationary object
If the number of anti-aliasing filters is reduced through multiplexing, then device area is reduced, but latency increases due to settling time requirements
Solution Approach 1:
The system performs preliminary charging of the anti-aliasing filter capacitor before each measurement cycle. By pre-charging the filter capacitor to the expected voltage level and allowing it to settle beforehand, the system eliminates the need for long settling times after multiplexing switches change state, thereby reducing measurement latency while maintaining area efficiency.
Solution Approach 2:
The measurement system maintains continuous operation by keeping the anti-aliasing filter continuously charged and ready. The switch matrix and control logic are designed to minimize interruptions and maintain the filter in an active, charged state, ensuring that measurements can be taken immediately when needed without waiting for capacitor charging cycles, thus reducing latency.
3Area of stationary object
If a single anti-aliasing filter is shared among multiple cells, then device area is reduced, but complexity of switching and control increases
Solution Approach 1:
The switching control system is segmented into modular components: a switch matrix with individual controllable switches for each cell-filter connection, a control logic unit that manages switch states, and a timing control module that coordinates measurement cycles. This segmentation makes the complex switching control more manageable and implementable through systematic design.
Solution Approach 2:
A control logic intermediary is introduced to manage the complexity of switching between multiple cells and a single filter. This intermediary component coordinates the switch states, timing sequences, and measurement scheduling, isolating the complexity from the core measurement function and making the system easier to control and debug.
Data Source
AI summary
A battery powered system includes a voltage level shifter, an anti-aliasing filter, a pair of switches, a unity gain differential buffer, a second pair of switches, and an analog-to-digital converter. The first pair of switches couple the differential output port of the voltage level shifter to the differential input port of the anti-aliasing filter. The second pair of switches couple the differential output port of the anti-aliasing filter to the differential input port of the unity gain differential buffer. The analog-to-digital converter is coupled to the differential output port of the unity gain differential buffer.