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From Wiki:4 A' N9 R5 b- C. B4 u
! o- ? L' f, @" XUSB supplies bus power across VBUS and GND at a nominal voltage 5 V ± 5%, at supply, to power USB devices. - {, J4 p, ^, Z% E; y5 o7 u
Power is sourced solely from upstream devices or hosts, and is consumed solely by downstream devices. . x' }$ L8 Z7 ^) ~
USB provides for various voltage drops and losses in providing bus power. 1 N; G* R% e5 f; E! q# W0 Q) m" m5 s
As such, the voltage at the hub port is specified to be in the range 5.00 +0.25 / −0.60 V by USB 2.0, and 5.00 +0.25 / −0.55 V by USB 3.0. 0 s- w& k& G: r$ o, i
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Normal USB port:. q' B; X1 {0 b# g( Q
5.0 +0.25 / -0.25 V
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9 J9 |( m" A' w: @Hub port:2 b0 ?7 f$ H4 ~2 g
USB 2.0: 5.0 +0.25 / -0.6 V# z/ y3 h" @0 h7 y# u% A3 }
USB 3.0: 5.0 +0.25 / -0.55 V |
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