TUSB4020BI-Q1: TUSB4020BI Q1 Hub not detecting

Please check this. Also I tried by removing SMBUS pull down resistor.

Thanks.

VBUS looks ok. Does the hub still not connect? What's the crystal circuit look like? Is there a good thermal pad connection under the hub?

Regards,
JMMN

No. I have assembled one PCB which is not working. Here I have attached crystal circuit and thermal pad for hub. thermal pad is both on top and bottom side of PCB with vias and those vias are not tented (masked).

I will check with another PCB. For the up stream port I am soldering wires on PCB, I guess there won't be any problem with that because I am not connecting long cable initially. And I have checked connections of soldered wire. Also would like to know how much distance the hub can cover.

I will check whether the clock starts or not and get back to you.

Thanks,

Nilam

I have replaced the 10K resistor in divider now USB is detected but showing as unknown USB device. Also showing as device descriptor request failed after I tried to update drivers. Voltage on VBUS is 400-440 mV.

Also USB_R1 voltage is 500 mV.

Thanks,

Nilam

Hi Nilam,

I would expect VBUS to be closer to 500 mV. Can you check that DP and DM are not swapped?

Regards,
JMMN

Hi,

According to color coding,  when i connect cable to device it does not detect. But when i swap those cables  it is detected as unknown USB device.

Thanks.

Hello JMMN,

I have checked crystal frequency on MSO, it properly showing 24MHz. But there are no pulses on DM and DP up. It is still showing as unknown USB device and give device descriptor request failed error. No use of updating drivers neither worked reinstalling.

Thanks,

Nilam 

It sounds like a USB DP/DM connection issue, not a descriptor issue.  Can you confirm if DP goes high (3.3V) when the hub is connected?  It may pulse high and then go low or go high and stay high (suspend).

Regards,

JMMN

hello,

Yes, DP continuously stays at 3.3 V and DM stays at 0. Also the down port switching voltage gradually goes down from 5 to 4.4 and then down to 3.4 V.

All points like VBUS, USB_R1, Crystal frequency, 3.3 V and 1.1 V are ok. still it is detected as unknown USB device. I tried updating it's drivers manually but it also failed.

Thanks,

Nilam

Hi Nilam,

It appears that the hub goes to suspend mode. Can you confirm that SMBUSz is high? Does the downstream port power turn on when the upstream port is connected? What is sourcing the 5V to the downstream ports? Can you attach the complete schematic? If you can't post on a forum, please accept my friend request and send it to me directly.

Thanks,
JMMN

hello,
I have removed SMBUSz pull down resistor. but still it is low. Downstream port power turns on with 4.8-4.9 v on DS ports.

Thanks,

Nilam

Hi Nilam,

The TUSB4020B will drive the SMBUSz low after power on reset, as long as the pulldown resistor is removed the SMBUSz will be sampled high at power on reset. The schematic shows battery charging is enabled on the downstream ports, so you should see downstream port power should be on when there is no host connected, then pulse low when the host is connected and finally turn back on once enumerate completes. Do you see that port power behavior?

Regards,
JMMN

Hi JMMN,

As far as DS ports are concerned , it's behavior is without host it shows 5V and as I connect host it's voltage gradually reduces to zero and never returns to 5V again. I have to disconnect hub and connect it again to make DS ports power ON. Just wondering if this is due to ferrite beads or TVS diodes or is it a current issue.

Thanks,

Nilam

Hi Nilam,

Ok, this is the expected behavior if enumeration fails.  It looks like there is some sort of connection issue between the hub and the host, how long is the cable?  Are you seeing this issue on all platforms and across multiple units?

Regards,

JMMN

Hi JMMN,

Connection cable is very short like 50-60 cm. But it is soldered connection. I have assembled two PCBs, the other one is not detecting at all. track widths of differential pair are 6 mils with 8 mils separation. Is it feasible?

One device is detected but it has descriptor issue, it's battery charging does not work . while the other one is not detected but its battery charging works.

Thanks,

Nilam.

hi JMMN,

On that note , how long cable can be used at upstream port?

Thanks,
Nilam.

For USB 2.0, max cable length is 5 meters.

REgards,

JMMN