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The Designer's Guide Community Forum › Design › High-Speed I/O Design › USB 2.0 Low Speed Buffer Up/Down Stream Difference
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USB 2.0 Low Speed Buffer Up/Down Stream Difference (Read 3620 times)
neoflash
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USB 2.0 Low Speed Buffer Up/Down Stream Difference
Jun 03rd, 2010, 5:10pm  
Why in USB 2.0 spec, the drive loading capability is different between up and down steam facing ports?

For downstream, it is 200-600pF while for upstream it is 50-150pF?
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supermoment
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Re: USB 2.0 Low Speed Buffer Up/Down Stream Difference
Reply #1 - Jun 11th, 2010, 6:14am  
It gives more stringent rules to downstream ports (host & HUB) since they have power supply.
While upstream ports normally is a device which get power from host or HUB. So their driving capability is less.

Hopefully it is correct.
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