Power savings for universal serial bus devices
First Claim
1. An apparatus comprising:
- a Universal Serial Bus (USB) transceiver of a USB host controller, wherein the USB transceiver has a differential output;
a first pull-down resistor;
a first switch to electrically couple the first pull-down resistor to a positive terminal of the differential output in response to a first switch control signal;
a second pull-down resistor;
a second switch to electrically couple the second pull-down resistor to a negative terminal of the differential output in response to a second switch control signal; and
a detachment module to selectively determine whether a USB device is electrically coupled to the differential output by checking a voltage at the differential output while at least one of the first switch control signal or the second switch control signal is asserted,wherein the detachment module determines whether the USB device is electrically coupled to the differential output bychecking the positive terminal when the USB transceiver is in a full-speed idle state, andchecking the negative terminal when the USB transceiver is in a low-speed idle state.
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Accused Products
Abstract
An apparatus includes a Universal Serial Bus (USB) transceiver of a USB host controller, a first pull-down resistor, a first switch, a second pull-down resistor, a second switch, and a detachment module. The USB transceiver has a differential output. The first switch electrically couples the first pull-down resistor to a positive terminal of the differential output in response to a first switch control signal. The second switch electrically couples the second pull-down resistor to a negative terminal of the differential output in response to a second switch control signal. The detachment module selectively determines whether a USB device is electrically coupled to the differential output by checking a voltage at the differential output while at least one of the first switch control signal or the second switch control signal is asserted. The detachment module determines whether the USB device is electrically coupled to the differential output by checking the positive terminal when the USB transceiver is in a full-speed idle state and by checking the negative terminal when the USB transceiver is in a low-speed idle state.
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Citations
13 Claims
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1. An apparatus comprising:
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a Universal Serial Bus (USB) transceiver of a USB host controller, wherein the USB transceiver has a differential output; a first pull-down resistor; a first switch to electrically couple the first pull-down resistor to a positive terminal of the differential output in response to a first switch control signal; a second pull-down resistor; a second switch to electrically couple the second pull-down resistor to a negative terminal of the differential output in response to a second switch control signal; and a detachment module to selectively determine whether a USB device is electrically coupled to the differential output by checking a voltage at the differential output while at least one of the first switch control signal or the second switch control signal is asserted, wherein the detachment module determines whether the USB device is electrically coupled to the differential output by checking the positive terminal when the USB transceiver is in a full-speed idle state, and checking the negative terminal when the USB transceiver is in a low-speed idle state. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method comprising:
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electrically coupling a first pull-down resistor to a positive terminal of a differential output of a Universal Serial Bus (USB) transceiver of a USB host controller in response to a first switch control signal; electrically coupling a second pull-down resistor to a negative terminal of the differential output of the USB transceiver in response to a second switch control signal; and selectively determining whether a USB device is electrically coupled to the differential output by checking a voltage at the differential output while at least one of the first switch control signal or the second switch control signal is asserted, wherein determining whether the USB device is electrically coupled to the differential output includes checking the positive terminal when the USB transceiver is in a full-speed idle state, and checking the negative terminal when the USB transceiver is in a low-speed idle state. - View Dependent Claims (8, 9)
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10. A computer program stored on a computer-readable storage device and executable by a processor, the computer program comprising:
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instructions for electrically coupling a first pull-down resistor to a positive terminal of a differential output of a Universal Serial Bus (USB) transceiver of a USB host controller in response to a first switch control signal; instructions for electrically coupling a second pull-down resistor to a negative terminal of the differential output of the USB transceiver in response to a second switch control signal; instructions for determining whether a USB device is electrically coupled to the differential output by checking a voltage at the differential output while at least one of the first switch control signal and the second switch control signal is asserted; and instructions for determining whether the USB device is electrically coupled to the differential output by checking the positive terminal when the USB transceiver is in a full-speed idle state, and checking the negative terminal when the USB transceiver is in a low-speed idle state. - View Dependent Claims (11, 12)
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13. An apparatus comprising:
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a Universal Serial Bus (USB) transceiver of a USB host controller, wherein the USB transceiver has a differential output; a first pull-down resistor; a first switch to electrically couple the first pull-down resistor to a positive terminal of the differential output in response to a first switch control signal; a second pull-down resistor; a second switch to electrically couple the second pull-down resistor to a negative terminal of the differential output in response to a second switch control signal; a detachment module to selectively determine whether a USB device is electrically coupled to the differential output by checking a voltage at the differential output while at least one of the first switch control signal or the second switch control signal is asserted; and a switch controller to negate the first switch control signal and the second switch control signal when a first predetermined period elapses after the first switch control signal and the second switch control signal are asserted, wherein the detachment module waits for a second predetermined period before again determining whether the USB device is electrically coupled to the differential output, and wherein a duty cycle of the first predetermined period and the second predetermined period determines a value of current through the differential output.
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Specification