A user wants to charge a smartphone by plugging it into a USB hub used by a keyboard and a mouse. Which of the following issues would prevent this from working?
a. Hub is self-powered
b. Hub is bus-powered
c. Smartphone not compatible with USB charging
d. None of the above.
B A bus-powered hub provides only 100mA of power to each device connected to it. This is enough current for most mice and keyboards, but is far short of the 500mA of power needed for charging a smartphone. Many hubs used for keyboards and mice are bus-powered. A self-powered hub has an AC adapter so it can provide 500mA of power (USB 1.1, 2.0 devices) or up to 900mA of power (USB 3.0 hub and devices) per port. Smartphones are compatible with USB charging if enough power is available.
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