Method and apparatus of disabling the pull-up on a USB type of data line
OwnerGregory M. Allen, Don I. Jacob +1inventors
InventorsGregory M. Allen, Don I. Jacob, Michael C. Burnside
Life of this patent
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Abstract
A method and apparatus for enabling and disabling a pull-up resistor connected to a data line of a universal serial bus is provided for universal serial bus devices that are provided with an external power source. A transistor is interconnected between VBUS of the universal serial bus connection and the input of an integrated circuit such that the voltage on the input of the integrated circuit is proportional to the voltage on VBUS. Thus, when VBUS is not present the pull-up resistor on the data line is disabled and subsequently enabled when VBUS exceeds a predetermined threshold.
Claims31
An circuit for disabling a pull-up resistor connected to a data line of a universal serial bus device, comprising:
- a universal serial bus connection comprised of at least one power source and at least two data lines;
- an integrated circuit connected to the at least two data lines and having an input;
- an external power supply connected to the integrated circuit;
- at least one transistor interconnected between VBUS and the input, the power source and the integrate circuit for controlling voltage to the input of the integrated circuit corresponding to the voltage of VBUS;
- and
- a pull-up resistor connected between the application specific integrated circuit and a data line of a USB connection, the state of the pull-up being controlled by the application specific integrated circuit depending upon the voltage on the input.
A method of disabling a pull-up resistor connected to a data line of a universal serial bus device comprising a universal serial bus connection comprised of a power source, at least two data lines, a pull-up resistor connected to one of the at least two data lines, an external power supply and an integrated circuit having an input, the method comprising:
- detecting the presence of a voltage of the at least one power source;
- applying a voltage to the input of the integrated circuit that is proportionate to the voltage on the at least one power supply;
- determining if the voltage on the input represents a logic one or a logic zero;
- and
- enabling the pull-up resistor if the voltage on the input represents a logic one and disabling the pull-up resistor if the voltage on the input represents a logic zero.
A method for preventing malfunctions in a data transmission system which transmits digital signals along a data bus between a host computer and a peripheral device wherein the peripheral device may receive power from the host computer or alternatively from an external power source, comprising
- interconnecting a transfer bridge circuit between the host computer and the peripheral device, the bridge circuit having a first interface between the bridge circuit and the host computer, a second interface with a protective circuit, and a third interface with the peripheral device electronics,
- providing a pull-up resistor connected in a separate line between the first interface and the data bus,
- sensing whether power is being supplied along a power line from the host computer to the peripheral device, and if appreciable power is not detected in the host power line, then
- deactivating the pull-up resistor to prevent any malfunction from occurring.
Dependencies are inferred from the claim text.