TUSB4020BI: TUSB4020BI Malfunction

HI Rohini:

   Can you send schematic for review first?

Best

Brian

Hi Brain,

Please find the sch below

Thanks,

Rohini

Hi Rohini:

   I didn't find any issue in schematic.

    Did FT4232 and CY7C68013A connected to hub downstream ports? Do they need VBus to start working?

   Can you take waveform for  1.1V , 3.3v and GRSTz  signal?

Best

Brian

Hi Brain,

Yes, FT4232 and CY7C68013A are connected to HUB downstream ports. Those devices are self powered. Taking powers from Board rails and don't need VBUS

PFA- 1.1V,3.3V and GRSTz Power up sequence

Note:

1. on some board we see GRSTz is going high even before 3.3V is not in stable state . but we do not see any issue with that boards

When we tried increase the capacitance value to 2.2uF on GRSTz Pin, we didn't see any change in the HUB behavior

2. Previously we had mostly only CY7C68013A  on the downstream path and kept FT4232  on reset in most of our boards

Now we have enabled both FT4232 and CY7C68013A(both are out off reset) in our latest design. We started seeing this issue on this revision boards

Thanks,

Rohini

Hi Rohini:

   Power on sequence looks ok from your waveform .

   What is fail rate from tested board? Can you send downstream port schematic as well?

Regards

Brian