Localized LFPS Signal Generator for Low Power USB Out-of-Band Communication
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Solution Overview
Problem
High-power consumption in USB 3.0 devices when sending out-of-band 'ping' messages to maintain connection with a host device, particularly in low-power modes, is a concern for portable devices seeking to minimize power usage.
Innovation Solution
A localized low-frequency periodic signaling (LFPS) sideband signal generator is used in a USB transceiver that remains operational while the bulk of the transceiver is in low-power mode, employing a small state machine clocked by a reference clock to selectively power up only the necessary circuitry for sending out-of-band messages, thereby reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the entire transmitter and clock multiplication unit are woken up to send ping messages, then out-of-band communication is achieved, but power consumption increases significantly
Solution Approach 1:
The transmitter is segmented into multiple independent components: the clock multiplication unit (CMU), the data path circuitry, and the out-of-band signal generator. During low-power mode, only the essential out-of-band signal generator remains active to send ping messages, while the CMU and data path circuitry remain powered down. This segmentation allows the system to maintain connection reliability through out-of-band communication without incurring the full power cost of waking up the entire transmitter.
2Ease of operation
If the clock multiplication unit and transmitter are activated for out-of-band signaling, then communication capability is maintained, but power penalty increases
Solution Approach 1:
The out-of-band signal generation capability is extracted as a separate, independent function from the main transmitter chain. The out-of-band signal generator can operate autonomously using a reference clock source, without requiring the clock multiplication unit or the main transmitter to be activated. This extraction allows the system to maintain communication capability for connection maintenance while avoiding the power penalty of activating the entire transmitter system.
3Use of energy by moving object
If a localized LFPS sideband signal generator is used instead of the entire transmitter, then power consumption is reduced, but device complexity must be managed
Solution Approach 1:
Instead of activating the entire high-power transmitter system, the patent implements a localized out-of-band signal generator that produces only the necessary low-frequency periodic signaling (LFPS) sideband signals. This localized approach concentrates the power consumption and functional complexity only where absolutely necessary for connection maintenance, while keeping the rest of the transmitter chain in a low-power state. The localized generator uses a reference clock source and minimal circuitry to produce the required out-of-band signals.
Data Source
AI summary
A signal generator circuit for reducing power consumption of out-of-band message communications between a first device including the signal generator circuit and a second device coupled to the first device comprises a switching circuit and a controller coupled to the switching circuit. The controller is operative to receive a reference clock signal and at least a first control signal indicative of a request for the first device to send a message to the second device when the first device is in a first mode of operation. The controller generates an output control signal and an output data signal. The output control signal is operative as a function of the first control signal to selectively power up the switching circuit and a transmitter driver during the first mode. The output data signal includes the message supplied to the transmitter driver for transmission to the second device during the first mode.