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TUSB8041: Device USB enumeration failed after plugging and unplugging host

Part Number: TUSB8041
Other Parts Discussed in Thread: TUSB542, TUSB522P

Hi Sir

We have use TUSB8041 solution in our project,and we found an issue during use.

The issue as belows:

The above figure is the System Block.

Host is pluggable.

1.1V and 3.3V power sources are always on.

Power of devices1~4 are always on.

When Host is unplugged, USB_VBUS is low.

When Host is plugged, USB_VBUS is high , HUBs start working, Devices1~4 will be enumerated.

The issue is:

After host is plugged in,some times, one of these devices(Device1~4) may fail to enumerate.

We have made the following attempts, but the issues have not been resolved.

Caes 1:

remove hub1,connect HOST directly to hub2,The situation of device enumeration failure still exists.

Case 2:

Using PWRCTL from hub1 instead of USB_VBUS of hub 2.The situation of device enumeration failure still exists.

Case 3:

Use USB_VBUS to Contrl the power of hub2.

when HOST is plugged,USB_VBUS is high,power of hub2 is on.

when HOST is unplugged,USB_VBUS is low,power of hub2 is off.

The situation of device enumeration failure still exists.

Could you teach me,why the USB enumeration of the device fails.

 

Thanks and best regards.