TUSB4020BI-Q1: Earthing issue causing problems to hub

Nilam Vilayatkar

Part Number: TUSB4020BI-Q1

Hello,

I am using TUSB4020BI-Q1 for USB extension. I am facing issue with hub IC failure on sites having earthing issues. I have not used series resistors on data lines. How does bad earthing affect USB Hub ? Any suggestions for solution will be appreciated.

Thanks in advance,

Nilam

over 6 years ago

0 JMMN over 6 years ago

TI__Guru 60870 points

Hi Nilam,

Can you describe the earthing issue? Are the data lines shorted to ground or is there ground noise?

Thanks,
JMMN

0 Nilam Vilayatkar over 6 years ago in reply to JMMN

Prodigy 245 points

hi,

Actually, their is problem in power at sites. Earth and ground noise that too power surges. I connect thermal printer to USB hub. It is working fine for 12 meter for other devices. Even those which are USB powered. But thermal printer has separate AC power. It skips prints. so after some time like in a day or so, USB hub starts not recognize problem. which ultimately is problem caused to data lines of hub. Not sure how it is causing problem to hub.

thanks.

P.S. I have connected PCB ground to Earth as per recommended in datasheet.

0 JMMN over 6 years ago in reply to Nilam Vilayatkar

TI__Guru 60870 points

Hi Nilam,

When this occurs is the hub permanently damaged? Or is it fixed after a power on reset? What kind of ESD protection is available in the system?

Regards,
JMMN

0 Nilam Vilayatkar over 6 years ago in reply to JMMN

Prodigy 245 points

hi JMMN,

Hub is permanently damaged and only protection to hub is TVS diode over data lines.

thanks,
Nilam

0 JMMN over 6 years ago in reply to Nilam Vilayatkar

TI__Guru 60870 points

HI Nilam,

It sounds like there is electrical over stress (EOS) of the DP/DM lines. Have you tried isolating the chassis ground from the digital ground? Are you using ferrite beads in the VBUS / GND lines? It is difficult to determine where the EOS is coming from in the system.

Regards,
JMMN

0 Nilam Vilayatkar over 6 years ago in reply to JMMN

Prodigy 245 points

Hi JMMN,

I am connecting chassis ground to digital ground through capacitor and resistor. I am using ferrite beads in 3.3v and 1.1v line and in the down port sopply as well. not in VBUS.

Thanks,

Nilam

0 Nilam Vilayatkar over 6 years ago in reply to Nilam Vilayatkar

Prodigy 245 points

0 JMMN over 6 years ago in reply to Nilam Vilayatkar

TI__Guru 60870 points

Hi Nilam,

It looks like the chassis ground circuit is good. Can you tell if the problem is the chassis ground or the digital ground? There's not a lot I can recommend without know which pins on the hub are damaged and what the source of the damaging signal is.

Regards,
JMMN

0 Nilam Vilayatkar over 6 years ago in reply to JMMN

Prodigy 245 points

Hi JMMN,

The problem is with chassis ground and only data lines are damaged.

Thanks and regards,

Nilam

0 Nilam Vilayatkar over 6 years ago in reply to Nilam Vilayatkar

Prodigy 245 points

Hi JMMN,

Can you suggest any other protection circuits for power and data lines?

Thanks and regards,

Nilam

0 JMMN over 6 years ago in reply to Nilam Vilayatkar

TI__Guru 60870 points

Nilam,

Your circuit looks like our typical recommended circuit, but some ideas for additional protection would be a ferrite bead between chassis ground and digital ground or adding ESD protection between the data lines and chassis ground.

We have not seen reports of earthing issues with this device in the past.

Regards,
JMMN

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TUSB4020BI-Q1: Earthing issue causing problems to hub