Latch Comparator Circuit for Compact Hall Sensor Hysteresis
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Solution Overview
Problem
Conventional digital output Hall sensors face challenges in achieving small die size, low power consumption, and competitive magnetic specifications while maintaining supply voltage rejection and temperature compensation, driven by commercial pricing and die size constraints.
Innovation Solution
The implementation of comparator circuitry with internal positive feedback and current-mirror loads provides hysteresis without the need for Schmitt triggers or feedback loops, along with new temperature compensation and supply voltage rejection circuitry, resulting in reduced power requirements and die size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional Schmitt triggers or feedback loops are used to provide hysteresis in digital output Hall sensors, then the hysteresis function is achieved, but the die size and power consumption increase
Solution Approach 1:
The patent combines the hysteresis function and amplification function into a single comparator circuit stage. The comparator inherently provides hysteresis through its positive feedback mechanism while simultaneously amplifying the differential signal from the Hall element, eliminating the need for separate Schmitt trigger circuits or feedback loops. This integration reduces the number of discrete components and overall die size while maintaining the required hysteresis functionality for digital output stability.
2Reliability
If precision on-chip voltage regulation is used to provide stable bias, then supply voltage rejection is improved, but die size and supply current increase
Solution Approach 1:
The patent employs dynamic biasing techniques where the comparator circuit adjusts its operating parameters based on the input signal level and supply voltage conditions. The bias current is optimized to provide sufficient supply voltage rejection while minimizing power consumption. The circuit operates at lower bias currents compared to precision voltage regulators, achieving acceptable supply voltage rejection through careful parameter selection and optimization of the comparator's operating point rather than through heavy-handed voltage regulation.
3Reliability
If multiple separate circuits (Schmitt triggers, feedback loops, voltage regulators) are used, then individual functions are achieved, but the overall device complexity and die size increase
Solution Approach 1:
The patent merges multiple functions into a single integrated comparator circuit: signal amplification, hysteresis generation, and digital output buffering. The comparator circuit inherently provides hysteresis through its positive feedback mechanism while simultaneously amplifying the differential signal from the Hall element. The output stage is directly coupled to provide digital output without requiring separate Schmitt trigger or feedback loop circuits, thereby reducing overall device complexity while maintaining all necessary functional performances.
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 digital output sensors with improved supply voltage rejection, temperature stability, and reduced cost, achieving latching behavior and competitive magnetic specifications in a compact design.
Implementation Method 1
When a current-carrying conductor or semiconducting Hall element is placed into a magnetic field, a voltage will be generated orthogonal to the direction of both the current and the magnetic field. This principle is known as the Hall effect.
Data Source
AI summary
A digital output sensor includes a sensing structure that outputs a differential sensing signal and includes at least one sensing element. An integrated circuit includes a substrate including signal conditioning circuitry for conditioning the sensing signal that includes a differential amplifier coupled to receive the sensing signal and provide first and second differential outputs and a comparator having input transistors coupled to receive outputs from the differential amplifier. The comparator also includes first and second current-mirror loads that provide differential drive currents and are coupled to the input transistors in a cross coupled configuration to provide hysteresis. An output driver is coupled to receive the differential drive currents. An output stage includes at least one output transistor which is coupled to the output driver for providing a digital output for the sensor. A voltage regulator is coupled to receive a supply voltage and output at least one regulated supply voltage.