TMOS Sensor Array Readout Circuit for Infrared Imaging
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Solution Overview
Problem
Existing front-end analog signal reading circuits for TMOS sensors face challenges such as difficulty in selecting individual pixels, complex biasing, self-heating reduction, and leakage issues, especially at high temperatures, which affect the accuracy and efficiency of infrared radiation detection.
Innovation Solution
A method and sensor device configuration that includes a bidimensional matrix of TMOS sensors with a biasing branch and multiplexing arrangement using shift registers and decoders to quickly read signals, reduce thermal constants, maintain proper biasing, and minimize temperature leakage, employing a Wheatstone-like bridge configuration and current mirrors to enhance signal processing and reduce dead-time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a bridge-like differential circuit is used to read TMOS sensor signals, then signal measurement is enabled, but pixel selection becomes difficult and device complexity increases
Solution Approach 1:
The sensor array is divided into multiple independently controllable pixels, each with its own selection mechanism. The patent implements this by providing control circuitry that can selectively activate individual pixels or groups of pixels, allowing precise selection without requiring complex bridge-like differential circuits for each pixel. This segmentation enables simple address-based selection of sensor elements.
Solution Approach 2:
The patent introduces control circuitry as an intermediary between the sensor array and readout system. This control circuitry receives selection signals and activates corresponding pixels through simple switching mechanisms, eliminating the need for complex differential circuitry at each pixel location. The intermediary control layer simplifies the overall system architecture while maintaining measurement precision.
2Reliability
If complex biasing circuits are implemented for TMOS sensors, then proper transistor biasing is achieved, but device complexity and leakage increase
Solution Approach 1:
The patent implements a universal biasing scheme where control circuitry provides biasing signals to multiple pixels simultaneously through shared signal paths. Instead of dedicated complex biasing circuits for each pixel, a single control system generates biasing signals that are distributed to all active pixels, reducing overall device complexity while maintaining proper transistor operation.
Solution Approach 2:
The patent combines multiple biasing functions into a unified control system. The control circuitry integrates pixel selection, biasing generation, and signal readout functions, eliminating the need for separate complex biasing circuits at each pixel. This merging of functions reduces device complexity and minimizes leakage paths while ensuring reliable transistor biasing.
3Measurement precision
If thermal insulation of TMOS is maximized, then temperature variation sensitivity improves, but thermal transient effects and dead-time increase
Solution Approach 1:
The patent implements periodic scanning of pixel groups, where different sets of pixels are activated in alternating time periods. During each period, only a subset of pixels is active and being read out, allowing those pixels to complete their thermal transient response before the next readout cycle begins. This periodic operation reduces thermal dead-time while maintaining high temperature sensitivity through proper thermal insulation.
Solution Approach 2:
The patent activates pixels in advance of the actual measurement readout, allowing sufficient time for thermal transients to settle before data collection begins. The control circuitry manages the timing of pixel activation and readout to ensure that measurements are taken after thermal equilibrium is reached, thereby reducing dead-time while preserving temperature sensitivity.
4Productivity
If rapid signal reading is implemented, then productivity increases, but thermal transient effects and leakage may increase
Solution Approach 1:
The patent divides the sensor array into multiple pixel groups that can be read out in sequence. Instead of attempting to read all pixels simultaneously (which would require complex high-speed circuitry), the system segments the readout process into manageable stages, achieving high overall productivity while allowing each group sufficient time for thermal stabilization and accurate measurement.
Solution Approach 2:
The patent implements continuous scanning operation where pixel groups are activated and read out in a continuous sequence without interruption. This continuous operation maintains high productivity by eliminating idle time between scans, while the controlled timing ensures that each pixel group completes its thermal transient before the next group is activated, thereby maintaining signal accuracy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables efficient and rapid signal reading from TMOS arrays, reducing thermal transient effects and leakage, thereby improving the accuracy and speed of temperature distribution imaging in infrared radiation detection.
Implementation Method 1
the TMOS sensor is configured to transmit the IR radiation to this 'mass' part, which becomes heated as a result
Implementation Method 2
The high thermal insulation with the rest of the die ensures that the amount of heat that the TMOS receives from the external quantity to be measured
Implementation Method 3
The temperature variations of the TMOS are converted into electrical signals thanks to the I-V characteristic of the transistor itself
Data Source
AI summary
Current signals indicative of sensed physical quantities are collected from sensing transistors in an array of sensing transistors. The sensing transistors have respective control nodes and current channel paths therethrough between respective first nodes and a second node common to the sensing transistors. A bias voltage level is applied to the respective first nodes of the sensing transistors in the array and one sensing transistor in the array of sensing transistors is selected. The selected sensing transistor is decoupled from the bias voltage level, while the remaining sensing transistors in the array of sensing transistors maintain coupling to the bias voltage level. The respective first node of the selected sensing transistor in the array of sensing transistors is coupled to an output node, and an output current signal is collected from the output node.