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?
Best Answer
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.