USB Control Circuit Adaptive Thresholding for Disconnection Detection
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Solution Overview
Problem
The challenge of accurately detecting USB device disconnection events in low-voltage ICs, where traditional methods fail due to insufficient current output and increased noise interference, leading to higher production costs from trimming and storage of disconnection detection thresholds.
Innovation Solution
A method and circuit for USB communication interface disconnection detection that sets a threshold voltage during a speed negotiation handshake stage by comparing amplitude voltages of chirp pair and packet signals, adjusting the threshold voltage adaptively to accurately detect disconnections without pre-trimming, thus reducing testing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the disconnection detection threshold is set near the upper limit (525-625 mV) to avoid noise interference, then false disconnection detection is reduced, but in low-voltage ICs the host cannot output enough current to raise the disconnection level to 800 mV, making detection unreliable
Solution Approach 1:
The patent changes the detection parameter from voltage amplitude to impedance measurement. By measuring the impedance of the USB device rather than relying on voltage amplitude, the system can accurately detect disconnection events without requiring high current output. The impedance measurement is performed during the speed negotiation handshake stage when the USB device is expected to provide a specific impedance value.
Solution Approach 2:
The patent replaces the traditional voltage-based detection mechanism with an impedance-based detection mechanism. Instead of using a comparator to compare voltage amplitude with a threshold, the system measures the real and imaginary components of the impedance and determines disconnection based on impedance magnitude and phase angle, which is more suitable for low-voltage ICs.
2Measurement precision
If trimming is performed on testing machines to set the optimal disconnection detection threshold for each IC, then detection accuracy is improved, but production testing cost increases and requires additional OTP or ROM storage
Solution Approach 1:
The patent enables the USB host to automatically determine the disconnection detection threshold through impedance measurement during the speed negotiation handshake stage, without requiring external trimming or pre-programming. The system self-calibrates by measuring the impedance characteristics of the connected USB device and setting the threshold accordingly, eliminating the need for costly production testing and OTP/ROM storage.
Solution Approach 2:
The patent performs impedance measurement and threshold determination during the speed negotiation handshake stage, which occurs before normal data transmission begins. This preliminary action allows the system to establish the detection threshold in advance without requiring separate trimming steps or additional memory storage, integrating the calibration process into the normal USB connection sequence.
3Adaptability or versatility
If the disconnection detection threshold is lowered to accommodate process variations, then detection coverage is improved, but the ability to counteract noise interference is reduced
Solution Approach 1:
The patent measures both the real and imaginary components of the impedance, effectively creating a two-dimensional representation of the USB device characteristics. By using both components to determine impedance magnitude and phase angle, the system can distinguish between genuine disconnection events and noise interference, providing robust detection that tolerates process variations without increasing susceptibility to noise.
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 reliable USB device disconnection detection with reduced production costs by eliminating the need for pre-trimming and storage of threshold values, ensuring robustness against noise interference and process variations.
Implementation Method 1
When the USB device is properly connected using the USB 2.0 communication protocol, the USB device will provide an impedance of 45 ohms on the data line. The 45 ohms impedance provided by the USB device, which, combined with the 45 ohms impedance provided by the host, results in a total impedance of 22.5 ohms on the data line.
Implementation Method 2
When the host sends out the SOF packet, the host will output a current of 17.78 mA to the data line, resulting in a voltage of 400 mV on the data line.
Implementation Method 3
the host sets a disconnection detection threshold, and a comparator compares a voltage on the data line with the disconnection detection threshold to detect the disconnection event
Data Source
AI summary
A detection method for USB communication interface disconnection includes: (a) detecting a first amplitude voltage of a chirp pair signal passing through the USB communication interface and setting a value of a threshold voltage to be less than the first amplitude voltage during a speed negotiation handshake stage; (b) detecting a second amplitude voltage of a packet passing through the USB communication interface during a data transmission stage; and (c) determining that a disconnection event has occurred in response to detecting that the second amplitude voltage is greater than the threshold voltage. A USB control circuit is also provided.