USB Data-Line Pull-Up Detection for Low-Power Host Connection
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Solution Overview
Problem
Existing USB capable devices require an extra status input to detect connection to a USB host or hub, which consumes power and is not always necessary.
Innovation Solution
Incorporating weak resistive pull-ups on the D+ and D− USB data lines in the USB capable device, coupled with strong pull-downs on the host or hub, allowing the device to detect connection changes without an additional status input, thereby powering up only when connected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an extra status input is used to detect USB connection, then connection detection is reliable, but device complexity and power consumption increase
Solution Approach 1:
The existing D+ and D- data lines are made to serve dual purposes: USB data communication and connection status detection. By adding weak pull-up resistors to these existing lines, the patent enables them to indicate connection status without requiring dedicated status input pins, thus reducing device complexity while maintaining reliable detection
Solution Approach 2:
The patent combines the connection detection function with the existing USB data lines by merging the status indication role into the data communication infrastructure. The weak pull-up resistors on D+ and D- lines allow these lines to simultaneously carry data and indicate connection state, eliminating the need for separate status inputs
2Use of energy by moving object
If USB peripheral is kept powered down for power saving, then power consumption is reduced, but connection detection capability is lost
Solution Approach 1:
The weak pull-up resistors are pre-configured on the D+ and D- data lines to maintain a high impedance state that indicates disconnection. This preliminary setup allows the system to detect connection status passively without requiring active peripheral components, enabling power-saving mode while preserving detection capability
Solution Approach 2:
The connection detection mechanism uses the inherent electrical characteristics of the USB data lines and the weak pull-up resistors to automatically indicate connection status. The system serves itself by using the data lines' own voltage states (influenced by host pull-down resistors) to trigger wake-up, eliminating the need for additional active detection circuitry
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 method conserves power by keeping the USB peripheral dormant until connection is detected, enabling efficient power management and normal USB communications without the need for an extra status input.
Implementation Method 1
adding very weak resistive pull-ups, e.g., 150,000 ohms, to the D+ and/or D− USB data lines of the USB peripheral located in the USB capable device will hold these data lines at substantially a positive supply voltage, Vdd, until the USB capable device is coupled to the USB host or hub USB port
Data Source
AI summary
A low power Universal Serial Bus (USB) capable device uses a weak pull-up resistance that is coupled to at least one data line of the USB for detection of when the USB capable device is connected to a USB host or hub. When the USB capable device is not connected to the USB host or hub, USB peripheral, including the USB transceiver, USB voltage regulator, serial interface and/or USB logic circuits required for USB operation may be powered down to conserve power drawn by the USB capable device. When the USB capable device is connected to the USB host or hub, a voltage from the weak pull-up will be significantly reduced, thus signaling that the USB peripheral and associated circuits should be powered up for normal USB operation.