USB Differential Transmitter RX-Detect Using Common-Mode Pulses
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Transmitters described in existing USB 3.1 standards may perform erroneous detection during the RX-Detect function due to noise influence on differential signal lines with AC coupling capacitors, leading to incorrect determination of receiver connection states.
Innovation Solution
Incorporating an output driver, termination resistors, a pulse generator, and a detector with a comparator and switches to manage common-mode pulses and voltage thresholds, ensuring accurate detection by differentiating between connected and disconnected receiver states through controlled pulse output and comparison processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If AC coupling capacitors are provided in differential signal lines for USB 3.1 signal transmission, then signal transmission capability is improved, but erroneous detection occurs during RX-Detect function due to noise influence
Solution Approach 1:
The transmitter outputs a common-mode pulse signal to the differential signal lines before performing RX-Detect to preliminarily charge the AC coupling capacitors. This preliminary action ensures that when the detector samples the signal, the capacitors are already charged, preventing erroneous detection caused by noise during the charging transient period.
Solution Approach 2:
The invention applies preliminary anti-action by pre-charging the AC coupling capacitors with a common-mode pulse before the actual detection process. This counteracts the potential noise influence that would otherwise cause erroneous detection, ensuring reliable receiver connection state determination.
2Reliability
If RX-Detect function is implemented to detect receiver connection state, then connection status monitoring is improved, but power consumption increases due to continuous detection operations
Solution Approach 1:
The detector samples the voltage level of the common-mode pulse only during specific periods when the pulse is output, rather than continuously. This periodic sampling approach maintains reliable connection status monitoring while significantly reducing power consumption by keeping the detector in an inactive state during intervals between pulse outputs.
3Measurement precision
If detector continuously monitors voltage level to improve detection accuracy, then detection precision is improved, but false detection occurs due to noise on differential signal lines
Solution Approach 1:
The invention uses a short-duration common-mode pulse that rapidly charges the AC coupling capacitors and then quickly decays. The detector samples the voltage level during this brief pulse window and before the noise becomes significant. This rushing through the detection process during the optimal time window achieves high detection precision while avoiding noise-induced false detection.
Solution Approach 2:
The common-mode pulse is output preliminarily to charge the AC coupling capacitors before the actual detection occurs. This preliminary charging action ensures that when the detector samples the signal, the capacitors are already charged, preventing erroneous detection caused by noise during the charging transient period.
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
The solution effectively suppresses erroneous detection by accurately determining the receiver's connection state, reducing power consumption and improving signal integrity by distinguishing between noise and actual signal changes.
Implementation Method 1
differential signal lines having AC coupling capacitors provided in middle of the differential signal lines
Implementation Method 2
a detector configured to output a detection result signal indicating a magnitude relationship between a voltage level of the common-mode pulse and a threshold
Data Source
AI summary
A transmitter includes: an output driver that outputs differential signals to differential signal lines; first termination resistors and a first switch which are provided in series between a first reference voltage input terminal to which a reference voltage is inputted and the differential signal lines; a pulse generator that outputs a common-mode pulse to the differential signal lines during a period during which a pulse output instruction signal is at a significant level; and a detector that outputs a detection result signal indicating a magnitude relationship between a voltage level of the common-mode pulse and a threshold, during a period during which the pulse output instruction signal is at a significant level, and outputs a detection result signal indicating that the voltage level of the common-mode pulse does not exceed the threshold, during a period during which the pulse output instruction signal is at a non-significant level.