Usb tv stick power surge on hub10/30/2023 ![]() The device descriptor(s) have an information on how much current it is expecting to use under full-functional mode, its maximum. USB devices must take only 100/150 mA from VBUS to respond with device descriptors. ![]() To prevent the hub upstream port (host downstream) from overloading, USB has a two-step mechanism.įirst step is an informative. Therefore the bus-powered hubs are allowed to allocate only a fraction of power that is normally available from normal ports (500 or 900 mA) and from self-powered hubs (powered from external AC-DC adapters). In this case the system knows (via hub descriptors) that this is bus-powered hub, and therefore it must have the natural limits of how much power can be theoretically taken from upstream, and delivered to downstream ports. ![]() This message usually appears when a system uses a certified bus-powered USB hub (hub power and power for all it's ports are coming from a single upstream cable from host).
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