TUSB8020B: connecting upstream to computer error

Hello Mahesh,

Did you change the crystal to the correct value of 24 MHz?  The hub will not work with a 25 MHz crystal.  If you have changed the crystal, can you confirm the states of DP/DM on the upstream port of the hub?

Regards,

JMMN

Hi,

i changed the oscilator with 24mhz,  now the device is not detected in computer at all, and tusb8020b ic also getting over heated, please guide.

thank you 

Hello Mahesh,

Please confirm that the hub has a good thermal pad connection to ground.  This is how the device is grounded and how heat is dissipated.

Regards,

JMMN

te_usb_testing.pdf

hi,

i have uploaded my pcb file, pls check

Hi Mahesh,

Are there vias to the ground layer  under the thermal pad of the hub?  You have confirmed that there are no shorts on the pins?  Does the hub work before it heats up?

Regards,

JMMN

hi sir,

there are no vias in thermal pad, 

shorts are not there on the pins,

hub detects at first through another hub to the computer, but when plugged in directly to the computer it will not detect, 

and when connected through another hub, the external devices are not detected.

Hi Mahesh,

How is the thermal pad of the hub connected?  It is the main ground for the device and the hub will not function well if it is not connected to ground.

Please confirm that VBUS is on to the downstream ports when the hub is detected behind another hub.  How is the hub powered...from VBUS or another source?

Regards,

JMMN

the thermal pad is connected to the common ground,

vbus is also connected in downstream, but 3.3v and 1.1 volts of tusb8020 is powered by external source, with all common grounded.

Can you check that the crystal is starting on the board, and check the status of USB_VBUS and USB_R1?  Also the values of DP and DM on the upstream port.

Regards,

JMMN