| 摘要 |
An intelligent level shifter may be added to adjust the voltage level on the data lines (D+ and D-) used for communications in USB systems, to address the issue of missing negative common-mode range as defined by the USB specification. The level shifter may be part of a port power controller that allows adaptive shifting of the signal level in accordance with the current levels drawn on the supply line by a device, for example during charging. The port power controller may be operated in systems enabled for battery charging, and may combine overcurrent sensing (current meter for VBus) and the routing of the D+ and D- lines (used for the battery charging protocol) into a single package. By varying the voltage levels on the D+ and D- data lines according to the drawn current levels, the performance of USB Hosts ports and USB Hub ports may be greatly increased.
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