i am using the GL850G in gang mode for a circuit without over current protection to extend my available USB ports. on power up the crystal starts oscillating for around 40ms then stops. then i using a external USB hub with a GL850G it is working correctly. my guess would be what it has something to do with the overcurrent protection? PWREN1# is always high, i also tried to pull-up/pull-down OVCUR1# but PWREN1# is not changing state. any ideas?

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  • \$\begingroup\$ When crystal stops, what is connected to upstream DP0/DM0 port? \$\endgroup\$ – Ale..chenski Nov 25 '16 at 17:54
  • \$\begingroup\$ DP0/DM0 is connected to a AT91SAM, but no problem if i connect instead a external USB Hub(same controller GL850G) to the same port so i think the controller is ok. \$\endgroup\$ – Tom Nov 25 '16 at 18:03
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    \$\begingroup\$ What AT91SAM is doing on power up, how long does it take to boot and start USB activity? How long do you wait while watching for crystal activity? What DP0 is doing? Does it come HIGH after power-up? \$\endgroup\$ – Ale..chenski Nov 25 '16 at 18:11
  • \$\begingroup\$ its takes round 7sec to boot. i can confirm when i short DP0 to ground clocks starts again. i separated the the hub circuit from the board and tried it on a pc but still (malfunctioned device), if the schematic is correct should i replace the ic? \$\endgroup\$ – Tom Nov 25 '16 at 21:21
  • \$\begingroup\$ And what happens on DP0/DM0 after 7sec? Does the host try to USB_RESET the link? On shcematics, reset drain resistor is missing. Also, you need to make sure that the IC is configured for 12MHz, not for other. You do have a working hub, right? Do you copied exactly the configuration/connections? \$\endgroup\$ – Ale..chenski Nov 25 '16 at 22:49

The crystal stops because the host is not ready to output any USB activity yet. This is the mandatory SUSPEND mode for all USB devices: when upstream port has no activity for more than 3ms, any USB device must enter SUSPEND mode, which usually requires clocks to stop. That's why XTAL stops. The initial state of upstream port on this hub should be DP0=pullup high. You will likely see XTAL activity again if you just short the DP0 to ground (which would simulate the USB_RESET bus state). The hub IC should wake up and start XTAL oscillations.

This crystal issue has nothing to do with ganged or other power modes. PWRENx port control outputs are HIGH because they are inactive, and will go LOW (to enable downstream power in case of downstream high-side power switches) after the hub will be enumerated and all ports will be enabled by host.


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