Hall Sensor Arrangement With Switchable Filter Capacitor
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Solution Overview
Problem
Existing Hall sensor arrangements in smart handheld devices and cell phones face challenges in providing sufficient resolution and robustness against environmental factors like dust, humidity, and light while maintaining power efficiency, due to issues such as offset voltage, sensitivity drift, and high power consumption.
Innovation Solution
A sensor arrangement utilizing multiple Hall sensors with a transconductance amplifier, filter stage, and capacitive analog-to-digital converter, where the filter capacitor acts as a sample and hold stage, and is connected switchably to reduce power consumption by temporarily powering down unnecessary circuits during measurement cycles, allowing for intrinsic matching and efficient processing of sensor voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If feedback loop and noise shaping are used to compensate for offset voltage and sensitivity drift, then measurement precision is improved, but use of energy increases
Solution Approach 1:
The patent implements periodic self-test cycles where the Hall sensor output is shorted and the measurement circuitry is reset at predetermined intervals. During normal operation, the sensor operates without continuous feedback loops. The periodic calibration sequence temporarily activates the measurement functions to characterize offset voltages and sensitivity drift, then stores these characteristics for compensation. This approach provides accurate compensation data while minimizing power consumption by keeping the sensor in a low-power state between calibration cycles.
2Measurement precision
If multiple Hall sensor devices are used to improve resolution, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple Hall sensor devices into a single integrated sensor unit with shared measurement circuitry. The Hall sensor array outputs are multiplexed through a single measurement function that sequentially or simultaneously characterizes each sensor element during self-test cycles. This merging approach achieves the resolution benefits of multiple sensors while minimizing circuit complexity by using common transconductance amplifiers, filter stages, and analog-to-digital converters for all sensor elements.
Solution Approach 2:
The measurement circuitry is designed as a universal system that can characterize all Hall sensor elements through a single self-test and calibration sequence. The same transconductance amplifier, filter stage, and ADC are used for multiple sensor devices, with multiplexing switches routing different sensor outputs to the shared measurement functions. This multi-functional design eliminates the need for separate measurement circuits for each Hall sensor, reducing overall device complexity while maintaining the ability to process signals from multiple sensors for improved resolution.
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 configuration enhances the resolution and accuracy of Hall sensor signals while significantly reducing power consumption by minimizing the need for buffering amplifiers and optimizing circuit usage, maintaining robustness and efficiency across varying environmental conditions.
Implementation Method 1
a plurality of Hall sensor devices which are each configured to provide a sensor voltage in response to a magnetic field intensity
Implementation Method 2
A filter stage of the sensor arrangement has a resistor and a filter capacitor which can be connected in parallel in a switchable manner
Data Source
AI summary
A sensor arrangement has a plurality of Hall sensor devices, each configured to provide a sensor voltage in response to a magnetic field intensity. A selection unit is configured to forward either of the sensor voltages in response to a selection signal. A transconductance amplifier is configured to generate a sensing current depending on a forwarded sensor voltage. A filter stage has a resistor and a filter capacitor connected in parallel in a switchable manner in response to a first switching signal. The filter stage is configured to generate a filtered voltage across the filter capacitor depending on a sensing current. A capacitive analog-to-digital converter has an input capacitor being connected to the filter capacitor in a switchable manner in response to a second switching signal. The analog-to-digital converter is configured to generate a digital sensor value based on a filtered voltage. The sensor arrangement further has a control circuit which is configured to generate the selection signal and the first and the second switching signals such that for each of the forwarded sensor voltages in a first time segment, the filtered voltage across the filter capacitor is generated, and in a second time segment, the input capacitor is connected to the filter capacitor.