US Patent:
20030158990, Aug 21, 2003
Inventors:
Gregory Allen - Layton UT, US
Don Jacob - Kaysville UT, US
Michael Burnside - South Weber UT, US
International Classification:
G06F013/14
H03K017/16
H03B001/00
US Classification:
710/305000, 326/030000, 327/108000
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.
