Segmented Sample-and-Hold Readout With Dummy Cells for Offset Control
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Solution Overview
Problem
In optical sensor applications, such as LIDAR, it is impractical to have a high-speed ADC for every optical sensor due to die area and power constraints, necessitating a cost-effective method for sampling and processing multiple input signals efficiently.
Innovation Solution
A sample and hold system comprising a readout device, controller, array of segments with unit cells and dummy unit cells, and access switches, where the dummy unit cells absorb offset errors and allow switching between segments without impacting data cells, enabling efficient sampling and readout without the need for an ADC per input channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high-speed ADC is provided for every optical sensor, then measurement precision and processing speed are improved, but die area and power consumption increase significantly
Solution Approach 1:
The patent divides the array of optical sensors into multiple segments, where each segment can be independently connected to the readout device through segment switches. This segmentation allows sequential processing of multiple segments using a single ADC, reducing the number of ADCs required from one per sensor to one shared across all sensors while maintaining measurement precision through controlled segment-by-segment readout.
Solution Approach 2:
The readout device and ADC are designed to serve multiple functions by sequentially processing multiple segments. The segment switches enable the same readout device to handle different segments at different times, making the ADC a universal resource for all optical sensors rather than requiring dedicated ADCs for each sensor.
2Device complexity
If segment switches are used to connect segments to the readout device, then device complexity is reduced, but offset errors and noise are introduced during switching
Solution Approach 1:
The dummy unit cell acts as an intermediary between the segment switches and the readout device. By reading the dummy cell first after segment switching, the patent absorbs the offset errors and charge injection effects caused by the switches into the dummy cell readings, which are then discarded. This protects the subsequent actual sensor readings from being affected by switching artifacts.
Solution Approach 2:
The dummy unit cell creates a copy of the readout path that can absorb switching errors. The dummy cell is structurally similar to actual unit cells but serves a different purpose - to capture and isolate the harmful switching effects so they don't propagate to the actual measurement data.
3Area of stationary object
If multiple segments are processed sequentially through a single readout device, then die area is reduced, but processing time increases
Solution Approach 1:
The patent implements periodic action by systematically cycling through different segments in a structured sequence. Each segment is read out in turn through the segment switches, creating a periodic readout pattern that efficiently utilizes the single ADC resource while minimizing idle time and optimizing the processing schedule for multiple segments.
Data Source
AI summary
A sample and hold system, for capturing and reading at least one input signal. The system comprises a readout device, a controller, an array of segments comprising a plurality of unit cells and a dummy unit cell, and segment switches between the segments and the readout device. The controller is adapted for controlling the system such that: during an acquisition phase a trace of samples is taken from the input signal and held in the unit cells; during a readout phase the samples in the unit cells or in the dummy unit cells of a segment are read out by readout device; after opening or closing the segment switches the dummy unit cell, is the first cell which is read out by the readout device.