Sensor Interface Circuit With Dual DAC Architecture
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Solution Overview
Problem
Existing sensor interface circuits face challenges in providing both a substantial DC bias voltage and an accurate, high-resolution AC excitation signal to electrochemical sensors, as a single digital-to-analog converter (DAC) constrains the dynamic range, limiting the resolution of the AC excitation signal.
Innovation Solution
A sensor interface circuit architecture that separates the delivery of a DC offset bias voltage from the AC excitation signal, using a dual DAC configuration where one DAC generates the DC bias independently from the AC excitation signal, allowing for higher resolution in the AC signal without dynamic range constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single digital-to-analog converter (DAC) is used to generate both the DC bias voltage and the time-varying AC excitation signal, then the device complexity is reduced, but the resolution of the AC excitation signal is constrained by the available dynamic range of the DAC
Solution Approach 1:
The patent divides the single DAC function into two separate DACs: one dedicated to generating the DC bias voltage and another dedicated to generating the AC excitation signal. This segmentation allows each DAC to operate within its own dynamic range without interference, thereby improving the resolution of the AC excitation signal while maintaining reasonable device complexity through functional separation.
Solution Approach 2:
The patent extracts the DC bias voltage generation function from the AC excitation signal generation function. By taking out the DC component and handling it through a separate DAC, the AC signal path is freed from dynamic range constraints, enabling higher resolution AC excitation signals for precise impedance measurement.
2Device complexity
If a single DAC is used to provide both DC offset bias voltage and AC excitation signal, then the device complexity is reduced, but the measurement precision of sensor impedance is limited
Solution Approach 1:
The patent segments the impedance measurement function into two parts: DC bias application and AC excitation measurement. By using separate DACs for each function, the system can maintain a simple overall architecture while achieving high-precision impedance measurements through independent optimization of each measurement component.
Solution Approach 2:
The patent extracts the DC bias function from the measurement path, allowing the AC excitation and response measurement to occur in a dedicated path with higher resolution. This extraction enables precise impedance measurement by eliminating the dynamic range limitations that would exist in a combined single-DAC approach.
3Reliability
If a substantial DC offset bias voltage is provided to the electrochemical sensor, then the sensor operates effectively, but the dynamic range of the DAC is consumed, reducing the resolution of the AC excitation signal
Solution Approach 1:
The patent segments the voltage generation into two independent channels: one DAC dedicated to providing the substantial DC offset bias voltage for reliable sensor operation, and another DAC dedicated to providing high-resolution AC excitation signals for precise measurement. This segmentation ensures that the DC bias requirement does not compromise AC signal resolution.
Solution Approach 2:
The patent extracts the DC bias voltage provision from the AC excitation signal path, allowing the DC component to be handled separately by its own DAC. This extraction ensures that the substantial DC offset needed for sensor reliability does not consume the dynamic range of the AC excitation DAC, preserving high resolution for impedance measurement.
Data Source
AI summary
A electrochemical or other sensor interface circuit architecture can deliver substantial DC offset bias to an electrochemical or other sensor separately or independently from delivering a time-varying AC excitation signal, which can then be provided with higher resolution, which, in turn, can allow better resolution of the measured response signal providing the impedance characteristic of sensor condition. For example, a differential time-varying AC excitation signal for the sensor condition characteristic can be delivered separately and independently from a differential stable (e.g., DC or other) bias signal, such as by using separate digital-to-analog converters (DACs), so that providing the more stable signal does not limit the resolution and accuracy of the time-varying signal, such as by using up the dynamic range of a single DAC.