Passive USB Decoupling Detection Using Pull-Up Reference Comparison
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Solution Overview
Problem
Existing active detection methods for device decoupling in communication interfaces, such as USB devices, often interfere with normal operation and accurate measurement, making passive detection methods desirable to determine decoupling without applying a current to the coupling pin.
Innovation Solution
A circuit and system that includes a switch, analog-to-digital converter (ADC), digital-to-analog converter (DAC), and comparator to measure and compare a pull-up signal as a reference value, allowing for passive detection of a pull-down signal without affecting normal device operation, enabling continuous and repeated detection without interfering with the signal at the coupling pin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If active detection methods are used to detect device decoupling, then detection capability is improved, but normal operation and measurement accuracy are interfered with
Solution Approach 1:
The patent introduces an intermediary detection circuit that includes a switch, ADC, DAC, and comparator. This intermediary circuit measures the voltage at the coupling pin without directly interfering with the signal transmission. The switch connects the detection circuit to the coupling pin only during detection phases, and the ADC/DAC converts signals to digital format for processing by the controller, enabling passive detection that avoids interference with normal operation.
Solution Approach 2:
The detection is performed periodically rather than continuously. The controller controls the switch to connect the detection circuit to the coupling pin at specific intervals to measure voltage levels. This periodic sampling approach allows the system to detect decoupling events while minimizing interference with ongoing signal transmission and normal device operation.
2Difficulty of detecting and measuring
If current is applied to the coupling pin for detection, then decoupling detection is enabled, but measurement accuracy is degraded
Solution Approach 1:
The detection circuit utilizes the existing voltage conditions at the coupling pin caused by pull-up and pull-down signals from connected devices. Instead of applying its own current, the circuit passively measures the voltage level that naturally occurs during normal operation. The ADC converts this voltage to digital format, and the comparator compares it against reference values to determine coupling status, thereby achieving detection without degrading measurement accuracy through active current injection.
3Object-generated harmful factors
If passive detection is implemented, then interference with normal operation is reduced, but detection continuity is limited
Solution Approach 1:
The system maintains continuous monitoring capability through periodic detection cycles. The controller manages the switch to periodically connect the detection circuit to the coupling pin, ensuring that decoupling events are detected promptly while allowing normal signal transmission to continue uninterrupted between detection cycles. This continuous passive monitoring approach balances low interference with sustained detection capability.
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 transparent, ongoing, and non-intrusive detection of device decoupling, allowing devices to enter low-power modes or modify operations without disrupting normal operation or measurement accuracy.
Implementation Method 1
an analog-to-digital converter (ADC) comprising an input terminal coupled to the second node and configured to output a reference value in a digital format
Implementation Method 2
a digital-to-analog converter (DAC) comprising an input terminal configured to receive the reference value in the digital format
Implementation Method 3
a comparator comprising a first input terminal coupled to the second node, a second input terminal coupled to the output terminal of the DAC, and an output terminal
Data Source
AI summary
Aspects of the present disclosure provide for a method. In at least some examples, the method includes controlling a switch to decouple a first node at which a pull-up signal is present from a second node. The method further includes measuring and storing a value of the pull-up signal as a reference value. The method further includes controlling the switch to couple the first node at which the pull-up signal is present to the second node. The method further includes determining whether a pull-down signal is present at the second node by comparing the reference value to a value of a signal present at the second node.