TUSB2E22: TUSB2E22

Venkat Gurumurthy

Part Number: TUSB2E22

Hi,

We would like to have further information on the parametric measurement setup for the repeater. Please check below for the snapshot from the TUSB2E22 datasheet.

1) We need further description about the test channel.

2) Impedance conversion formula.

We also checked the Eval Board Schematic (check below)

eUSB

3) R5, R9 are 0ohm here and R6, R8 has been highlighted as DNI. Can we conclude that R6 and R8 resistors are required only for repeater eye diagram measurements where R5 and R9 need to be 22ohms?

4) For our on-board designs we can follow the EVB schematic with the 0ohm resistors for R5 and R9 and there will be no impedance mismatch issues.

USB2.0

5) There is no provision on the USB2.0 side on the EVB to populate 143ohm shunt resistors to GND and 15.8ohm series resistors for the Test Channel as per the parametric measurement information block diagram. So do we need to take care of the impedance matching for our designs on the USB2.0 side?

Please clarify.

Thanks,

Venkat

10 months ago

0 Nicholaus_Malone 10 months ago

TI__Mastermind 26090 points

Hi Venkat,

These are all good questions. I need to check internally, and I will follow-up in a couple of days with answers.

Regards,

Nicholaus

0 Nicholaus_Malone 10 months ago in reply to Nicholaus_Malone

TI__Mastermind 26090 points

Hi Venkat,

1) We need further description about the test channel.
The test channel in this case is a 2m cable on both sides.

2) Impedance conversion formula.
eUSB side converts 50ohm to 40ohm. The USB-side converts from 50ohm to 45ohm. I'm thinking this circuit is needed for impedance matching when using a BERT and oscilloscope as the Rx/Tx, which have 50ohm terminations, but I will check internally to confirm.

3) Yes, my understanding is the conversion is only needed when using a non-standard eUSB/USB source.

4) Correct.

5) Impedance conversion won't be needed if the Rx/Tx have the eUSB/USB termination impedances defined in the specifications. Any eUSB or USB host/device should have the correct terminations.

I will follow up on item 2. Let me know if you have any more questions.

Regards,

Nicholaus