Current-Mode ADC Architecture for Direct Multi-Sensor Current Conversion
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Solution Overview
Problem
Conventional analog-to-digital converters (ADCs) face issues of non-linearity, reliance on reference voltages, limited dynamic range, and complexity due to resistive dividers and intermediate voltage conversion stages, particularly in sensor systems.
Innovation Solution
A current-mode analog-to-digital converter (C-ADC) system that directly converts sensor currents into digital values without intermediate voltage conversion stages, using a balance current to counteract sensor current effects and modulate switch control signals, adaptable to various sensing methods including resistance, capacitance, and inductance sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a voltage mode ADC circuit is used with resistive dividers and intermediate voltage conversion stages, then the conversion of sensor signals to digital values is achieved, but the system complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the intermediate voltage conversion stages (such as transimpedance amplifiers, integrators, and passive element structures) from the conventional sensor system architecture. By directly converting sensor currents to digital values without these intermediate stages, the system complexity is reduced while maintaining the essential signal conversion function.
Solution Approach 2:
The patent creates a universal current-mode ADC architecture that can handle multiple sensor types (photodiodes, PIR sensors, resistive sensors, capacitive sensors, inductive sensors) through a single integrated circuit design. This multi-functional approach eliminates the need for separate voltage ADC circuits for each sensor type, reducing overall system complexity and cost.
2Ease of manufacture
If conventional voltage ADC circuits with intermediate conversion stages are used, then sensor currents can be converted to digital values, but the number of circuit components and system cost increase
Solution Approach 1:
The patent merges the functions of multiple separate components (sensor interface, signal conditioning, and ADC conversion) into a single integrated current-mode ADC circuit. This consolidation eliminates the need for separate transimpedance amplifiers, filters, rectifiers, and voltage ADC circuits, thereby reducing the total quantity of circuit components and associated system cost.
Solution Approach 2:
The universal current-mode ADC architecture serves multiple sensor types and multiple conversion functions within a single circuit, reducing the total component count across the entire sensor system while maintaining the ability to convert various sensor outputs to digital values.
3Measurement precision
If resistive dividers are used in sensor systems, then voltage division and signal conversion are achieved, but non-linearity between sensed resistance and converted voltage value occurs
Solution Approach 1:
The patent replaces the mechanical/resistive division approach with a current-mode computational approach. Instead of using resistive dividers that inherently produce non-linear relationships, the current-mode ADC uses current proportional-to-absolute-value (CTAB) circuits and digital processing to achieve linear conversion relationships between sensed resistance and digital output values.
4Reliability
If voltage mode ADC circuits with reference voltage sources are used, then voltage conversion is achieved, but reliance on stable reference voltages and limited dynamic range occur
Solution Approach 1:
The patent changes the fundamental operating parameter from voltage mode to current mode. This parameter change eliminates the need for stable reference voltages because current-mode circuits inherently provide immunity to power supply and reference voltage variations. The dynamic range is extended through the use of CTAB circuits and digital signal processing techniques that can handle a wider range of input current levels.
Data Source
AI summary
A device can include analog circuits formed with a substrate, including a comparator, analog switches, and a balance current circuit. A sensor current and balance current can be applied at an input of the comparator. The sensor current, balance current or both can be modulated with a switch control signal. Digital circuits can include switch control logic that generates the switch control signal in response to an output of the comparator and a modulation clock signal. Digital signal processing circuits can generate a multi-bit digital value from a bit stream output by the comparator circuit. The multi-bit digital value can be an analog-to-digital conversion of the sensor current. Corresponding methods and systems are also disclosed.