Yoctopuce Micro-USB-Hub-V2, User Manual

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2. Presentation
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If you use a non-shielded USB cable, or an improperly shielded cable, your system will work perfectly
well but you may not remain in conformity with the emission standard. If you are building a system
made of multiple devices connected using 1.27mm pitch connectors, or with a sensor moved away
from the device CPU, you can generally recover the conformity by using a metallic enclosure acting
as an external shield.
Still on the topic of electromagnetic compatibility, the maximum supported length of the USB cable is
3m. In addition to the voltage drop issue mentionned above, using longer wires would require to run
extra tests to assert compatibility with the electromagnetic immunity standards.
2.5. Limitations
Like all hubs on the market, the Micro-USB-Hub-V2 declares to the computer that it is self-supplied,
whether there is an active external power supply or not. Doing so prevents the computer to which the
hub is connected from deciding to limit the power of the peripherals that are connected to it to 100mA
for each port, which would generally render them unusable.
Moreover, as on most USB hubs on the market, this hub does not contain electronics to limit the
power consumption on down ports.