TUSB522P: Hardware related design issues.

Rhea Gao

Part Number: TUSB522P
Other Parts Discussed in Thread: TUSB1002A

Hi，

1. How many PCB Trace cables and several meters of Cable can this chip meet at the same time? We need 500mm PCB Trace+ 7M U3 cable.I wonder if this chip can meet our requirement, or if there is a better chip, we can recommend it;

2. Does the chip differential signal need only Tx with AC coupling capacitor or both Tx\Rx? Close to which side?

3.The left figure is the recommended application in the data manual, and the right figure is the schematic diagram of the Demo board

Thanks!

over 3 years ago

0 David (ASIC) Liu over 3 years ago

TI__Guru**** 177476 points

Hi,

Please see below for the cap placement

For the 500mm PCB Trace+ 7M U3 cable, are these on the TUSB522P input or the output side? How much is the loss of the 500mm PCB Trace+ 7M U3 cable?

Thanks
David

0 Rhea Gao over 3 years ago in reply to David (ASIC) Liu

Expert 2580 points

Hi David,

Before, the camera was directly connected to the USB chip directly to the PC. Now it is required to add a 500mm flexible cable to the conversion board, and then connect it to the PC.

The loss is shown below. Is this chip consistent? Or is there a better recommendation?

Thank you very much!

0 David (ASIC) Liu over 3 years ago in reply to Rhea Gao

TI__Guru**** 177476 points

Hi,

With ~4dB loss on both sides of TUSB522P, I do not see an issue of using TUSB522P for this design. They can use the TUSB522P EQ to compensate for the RX loss and DE to compensate for the TX loss.

Thanks

David

0 Rhea Gao over 3 years ago in reply to David (ASIC) Liu

Expert 2580 points

Hi David,

The USB cable at the output end is 5M-7m, so 0.6+3.6*5= 18.6dB, 0.6+3.6*7=25.8dB, the loss range is about 18.6-25.8dB, and the DE value is -6.2dB. Does it need to be >=18.6dB to compensate the loss? So can TUSB522P be used in this application?

Many thanks~

0 David (ASIC) Liu over 3 years ago in reply to Rhea Gao

TI__Guru**** 177476 points

Hi,

If you look at the USB loss budget for 5G, you will see that for Micro B connector, the max loss is 3.5dB.

If this particular cable has 18.6-25.8dB loss, then the cable is out of spec and TUSB522P will not able to support it.

Thanks

David

0 Rhea Gao over 3 years ago in reply to David (ASIC) Liu

Expert 2580 points

Hi David,

Which document is this figure in? Is there a suitable model recommended?

Many thanks!

0 David (ASIC) Liu over 3 years ago in reply to Rhea Gao

TI__Guru**** 177476 points

Hi,

Please see this link to the document, https://www.usb.org/sites/default/files/USB_3.1_Loss_Budget_Rev_1.0_-_2015-03-02.pdf. The document defines the max loss allowed for USB host, device, and cable at 5G and 10G.

Thanks

David

0 Rhea Gao over 3 years ago in reply to David (ASIC) Liu

Expert 2580 points

May I ask if the output of TUSB522P is a standard USB3.0 cable that can drive several meters, the data rate is 5Gbps, and the demand is 5m, can other chips reach this distance?

Thanks!

0 David (ASIC) Liu over 3 years ago in reply to Rhea Gao

TI__Guru**** 177476 points

Hi,

The TUSB522P is a redriver, its output can compensate either a cable or a PCB trace. The issue here is that the 5m cable is way out of spec in this particular case in terms of the insertion loss (18.6dB vs. the spec of 3.5dB).

We do not have a solution that can compensate 18.6dB of cable loss. You can do two things,

1. Change to a better quality cable to reduce its insertion loss

2. Put a TUSB1002A on the PC side and use its EQ and the TUSB522P DE to provide the compensation for the 18.6dB loss.

Is 18.6dB loss correct? Are you looking at the insertion loss at the Nyquist frequency (2.5GHz) of the 5G data rate?

Thanks

David

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TUSB522P: Hardware related design issues.