Pull-Up Resistor Measurement With Sampling-Capacitor Feedback
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Solution Overview
Problem
Existing methods for determining the resistance of pull-up resistors in sensors can cause system issues due to voltage drops that trigger false alerts and inaccuracies from differing supply voltages.
Innovation Solution
A decoder circuitry using a sampling capacitor and feedback path to generate current and voltage corresponding to the resistance of pull-up resistors, allowing for accurate determination without disrupting the sensor's operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing methods are used to determine resistance of pull-up resistors, then measurement can be performed, but voltage drops trigger false alerts and measurement inaccuracies occur
Solution Approach 1:
The system performs preliminary actions by charging the sampling capacitor before measurement to establish a known initial voltage state. This preliminary charging phase ensures that the capacitor starts at a predictable voltage level, allowing accurate resistance calculation without being affected by unknown initial conditions or voltage drops during the measurement process.
Solution Approach 2:
The sampling capacitor acts as an intermediary element between the pull-up resistor and the measurement circuitry. By using the capacitor to temporarily store voltage information, the system can indirectly measure resistance without directly applying current that would cause voltage drops and false alerts. The capacitor mediates the measurement process, isolating the pull-up resistor from direct measurement interference.
2Measurement precision
If measurement process is implemented, then resistance can be determined, but system complexity increases
Solution Approach 1:
The sampling capacitor and feedback path circuitry serve multiple functions: they enable resistance measurement, maintain voltage stability during measurement, and prepare the system for subsequent operation. By making this circuitry multi-functional, the system avoids adding separate dedicated measurement components, thereby limiting the increase in overall device complexity while achieving accurate resistance determination.
Solution Approach 2:
The measurement circuitry uses the existing pull-up resistor and capacitor in the system to perform self-measurement. The pull-up resistor, which was already present in the circuit for normal operation, is utilized for resistance measurement without requiring additional external components. The system measures its own electrical properties using existing elements, minimizing the added complexity.
3Difficulty of detecting and measuring
If voltage levels are changed for measurement, then resistance can be measured, but false alerts are triggered
Solution Approach 1:
The measurement process uses periodic action by alternately charging and discharging the sampling capacitor in controlled phases. During the charging phase, the capacitor charges to a known voltage without triggering alerts. During the discharge/measurements phase, the capacitor releases voltage through the pull-up resistor to enable resistance calculation. This periodic charge-discharge cycle allows measurement while maintaining voltage levels that do not trigger false alerts during normal operation.
Solution Approach 2:
The system performs preliminary charging of the sampling capacitor before the measurement phase to establish a safe initial voltage state. This preliminary action ensures that voltage changes occur in a controlled manner, starting from a known state, thereby preventing sudden voltage drops or spikes that would trigger false alerts during the actual measurement process.
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
Enables precise calculation of pull-up resistor resistance, setting accurate alert thresholds, and preventing false alerts by maintaining stable voltage levels during the measurement process.
Implementation Method 1
a capacitor having a first terminal and a second terminal, the first terminal coupled to the input/output pin and a second terminal coupled to a differential amplifier
Implementation Method 2
a differential amplifier having a first input terminal, a second input terminal, and an output terminal, the first input terminal coupled to the second terminal of the capacitor, the second input terminal coupled to a voltage source
Implementation Method 3
a resistor having a first terminal and a second terminal, the second terminal coupled to the common terminal
Data Source
AI summary
Methods, apparatus, systems, and articles of manufacture are described to determine electrical properties of external components. An example system includes a controller to output an indication to a first input/output pin based on a comparison of a temperature to a threshold; a first pull-up resistor having a first terminal coupled to the first input/output pin and a second terminal coupled to a voltage supply; and a resistor decoder to output a voltage having a voltage based on a resistance of the first pull-up resistor, wherein the controller is to determine the threshold based on the voltage.