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Method for reducing power consumption in USB host controllers through dynamic/opportunistic control of transmitter and receiver current sources

IP.com Disclosure Number: IPCOM000012022D
Publication Date: 2003-Apr-02
Document File: 5 page(s) / 112K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for reducing power consumption in universal serial bus (USB) host controllers through dynamic/opportunistic control of transmitter and receiver current sources. Benefits include improved power performance and improved functionality.

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Method for reducing power consumption in USB host controllers through dynamic/opportunistic control of transmitter and receiver current sources

Disclosed is a method for reducing power consumption in universal serial bus (USB) host controllers through dynamic/opportunistic control of transmitter and receiver current sources. Benefits include improved power performance and improved functionality.

Background

              Conventional buffers use dynamic throttling techniques to control power consumption. However, they are usually applied to CMOS-type buffers that have a negligible start up latency. Other interfaces, such has serial ATA, have low power modes that require software or device intervention. The power mode is not changed dynamically during data transfer.

              The Universal Serial Bus Specification Revision 2.0 was released on April 27, 2000 (see http://www.usb.org).                

              The power consumption in a USB 2.0 host controller is predominantly attributable to the DC current consumed by the transmitter and receiver circuits. One conventional method to control this consumption is to shut down the current sources used for the transmitters and receivers during the time that the bus is idle. However, the idle time between packets is typically small (in an efficient, heavily-used bus). The current sources in the transmitters and receivers have a non-zero start up latency, which reduces the opportunity to save power without increasing the idle time between packets and reducing bus efficiency.

General description

              The disclosed method reduces power consumption in USB host controllers through dynamic/opportunistic control of transmitter and receiver current sources. The method decreases power consumption in the presence of bus traffic without affecting bus efficiency and performance. The method takes advantage of the fact that the bus is half duplex. The transmitter and receiver are not required to be on at the same time, except in very specific circumstances. By turning off the transmitter while receiving and turning off the receiver while transmitting, power consumption can be reduced by approximately 50%.

              Additional factors that must to be handled include calculating when to turn the transmitters and receivers back on again. The procedure must ensure that the startup latency does not cause a decrease in bus efficiency even in the presence of packets that are shorter than expected.

Advantages

              Some implementations of the disclosed structure and method provide one or more of the following advantages: 

•             Improved power performance due to powering off and on transmitter and receiver current sources without affecting data flow

•             Improved functionality due to controlling the power consumption of USB 2.0 transmitters and received

Detailed description

              The disclosed method reduces power consumption in USB host controllers through dynamic/opportunistic control of transmitter and...