TUSB8020B: Hub connection issues

Mikael Carlsen

Part Number: TUSB8020B
Other Parts Discussed in Thread: TUSB8041

Hello,

I have a design with tusb8020b on my pcb. All downstream ports are connected to a CPU on the board (USB 2.0 via 2 external phy’s (usb3315)).

Both hub and phy´s are powered from the board. When cable is attached from computer to usb connector to hub, the hub shows up but no visible devices can be seen (enumeration doesn’t occur).

The configuration of the device is the default (no programming via smbus, eeprom etc).

Crystal is used as clock source.

I need help to solve why the hub doesn’t connect to the underlying devices.

Below is snip of the schematic;

Br Mikael

over 6 years ago

0 Mikael Carlsen over 6 years ago

Intellectual 270 points

0 Malik Barton57 over 6 years ago in reply to Mikael Carlsen

TI__Guru 64326 points

Hi,

What does the reset for your application look like? R177 is not necessary as TUSB8020B has a internal pull-up resistor to give the proper reset with 1uF cap. Can you confirm that the downstream devices are presenting proper USB termination?

0 Mikael Carlsen over 6 years ago in reply to Malik Barton57

Intellectual 270 points

Hi Malik,

Thanks for your reply. The reset from CPU is applied after the clock has stabilized.

The downstream devices (eg 2 USB3315) has internal termination (controlled by phy).

Br Mikael

0 Malik Barton57 over 6 years ago in reply to Mikael Carlsen

TI__Guru 64326 points

Hi,

Can you measure VDD33, VDD, and GRST to confirm that the reset follows the specifications listed in section 7.6 Timing Requirements, Power-Up of the datasheet? If TUEB8041 experiences an incorrect reset it can cause issues with enumeration. Can you use USBtreeview to see that is reported to the host by TUSB8041?

0 Mikael Carlsen over 6 years ago in reply to Malik Barton57

Intellectual 270 points

Hi,

I found that when I connected another external device to one of the downstream port of the hub (2.0), the device showed up in the device manager.

It seems like the hub is working correctly. Thanks for the support.

Br Mikael

Interface

Interface forum

TUSB8020B: Hub connection issues