| 摘要 |
A system and method for determining if a USB port can source sufficient current to charge a rechargeable battery at a predetermined peak current level. Detection circuitry is disposed between the USB port and the battery. The detection circuitry includes a current source that is controlled to provide to the battery an increasing current that is sourced by the USB port. As the source current is increased from an initial value to a predetermined peak current source value, the output voltage of the USB port is monitored. If the USB port output voltage drops below a specified threshold voltage before the current source has ramped to the peak current source value, the load current is removed from the battery and an indication is provided that the USB port cannot provide the specified current. The detection process is then repeated after a specified delay interval. If the current source ramps up to the peak source current value and the USB port voltage has not decreased below the specified threshold voltage, charging of the rechargeable battery from the USB port continues at the peak source current.
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