Sensor Bridge Readout Using Time-Domain Threshold Conversion
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Solution Overview
Problem
Existing methods for digitizing the differential output of sensor circuits or bridge circuits with two excitation nodes and two readout nodes are limited in terms of conversion speed, power consumption, accuracy, and footprint, offering room for improvement and alternative solutions.
Innovation Solution
A method and circuit for providing a digital value indicative of a physical quantity measured by a sensor or bridge circuit, involving the application of a time-varying biasing signal to the excitation nodes, generating time-varying output signals at the readout nodes, and determining a digital value based on specific time, count, or index values related to events where these signals pass threshold signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a classical ADC is used to digitize the differential output of a sensor circuit or bridge circuit, then conversion accuracy can be achieved, but conversion speed is limited and power consumption is high
Solution Approach 1:
The patent changes the fundamental parameter of the biasing signal from static to time-varying (e.g., sinusoidal, triangular, or exponential waveforms). This transformation enables the system to encode the differential voltage information in the timing or phase domain rather than directly in amplitude, allowing for faster conversion speeds while maintaining accuracy through correlation-based or threshold-crossing detection methods
Solution Approach 2:
The patent replaces the classical ADC mechanical/electronic conversion process with a time-domain measurement approach. Instead of directly converting voltage amplitude to digital values through complex analog circuits, the system uses time-varying excitation and measures timing parameters (such as zero-crossing times or peak detection times), which can be processed more quickly and with lower power consumption
2Measurement precision
If a classical ADC circuit is implemented, then digitization functionality is provided, but the circuit footprint is large and power consumption is high
Solution Approach 1:
The patent extracts the essential measurement information (differential voltage) from the complex ADC conversion process by using time-varying excitation. The system only needs to measure timing parameters or threshold crossing points rather than performing full amplitude conversion, thereby eliminating the need for large ADC circuits while retaining the core digitization functionality
Solution Approach 2:
The patent employs simple, low-cost measurement techniques such as threshold comparators and timing circuits instead of expensive, complex ADC circuits. These simpler components consume less power and occupy smaller area, sacrificing some of the advanced features of full ADCs while maintaining sufficient measurement capability for the application
3Productivity
If a time-varying biasing signal is applied to the excitation nodes, then conversion speed and power efficiency are improved, but the circuit complexity increases
Solution Approach 1:
The patent employs periodic time-varying biasing signals (such as sinusoidal or triangular waveforms) to excite the sensor circuit. This periodic excitation creates predictable, repeating patterns in the output signals that can be easily detected and measured using simple threshold comparators or zero-crossing detectors, thereby achieving fast conversion without requiring complex processing circuits
Data Source
Figure 1~2A
Figure 2B~3
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AI summary
A method (1000) of providing a digital value (Dout) indicative of a physical quantity to be measured by a sensor circuit or a bridge circuit that has two excitation nodes (E1, E2) and at least one output node (RO1, RO2), comprising the steps of: a) applying (1002) a time-varying biasing signal to the excitation nodes, causing at least one output-node to provide a time-varying output signal (Vp, Vn); b) determining (1002) a first time value (T1) or a first count value (N1) or a first index (Index1) related to a first event (event1) at which the first output signal (Vp) passes a first threshold signal (Vt1); c) providing (1003) a digital value (Dout) indicative of the physical quantity to be measured based on said at least one time value (T1) or count value (N1) or index value (Index1).