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USB2513B overcurrent

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dscheiwiller
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2019/08/28 07:17:02 (permalink)
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USB2513B overcurrent

Hi there

I have a problem with USB2513B. On port 2 I connect a LTE module via mPCIe connector. When then connecting the hub to the host PRTPWR2 is toggled although OCS_N[2] is pulled-up to VDDC33. The circuit works fine with other modules. What else than OCS_N[2] causes the hub to pull PRTPWR2 low?
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    roundrocktom
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    Re: USB2513B overcurrent 2019/09/18 09:12:48 (permalink)
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    What else is connected to the hub?
     
    If you are bus-powered, the host may not connect additional devices. Current isn't measured but reported during USB Enumeration. So the Host will not let other devices connect.
     
    I'm allowed 500mA total (USB 2.0 spec). The Hub will indicate it's configuration and power consumption. Let's say 84mA for the Hub; Host then knows "I have 416 ma available for plugged-in devices".
     
    So it device plugged into port one reports, "I need 200ma" Host goes, OK I have 216ma available."
     
    If a device plugs into Port 2, it will enumerate, then tell the host sees it is requesting 240mA it will disconnect it.
    The solution is to use external 5V and have the hub report "self-powered."  Now it knows the hub is typically on the motherboard and you have a power supply to supply the ports, or are using an external power supply
     
     
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