TUSB1142: Design Parameters

Mochizuki-san

Mochi said:

1. "Minimum distance of the AC capacitors from TUSB1142, LAC-CAP : 0.4 inches"

What is reason of minimum pattern length 0.4 inches requirement between PIN to CAP terminal inside of 2 inches <= XAB, <= 12 inches - XCD ?

Is that considering of impedance matching or something?   

The minimum distance shown in the datasheet is a guideline to reduce the effects of return loss, but this is not a hard requirement.

Mochi said:

2. "CAC-USB1 AC-coupling capacitor (75 nF to 265 nF)"   "CAC-USB2 AC-coupling capacitor (297 nF to 363 nF)"

Those CAPs are purposing just DC blocking, but why it have such a narrow acceptable tolerance?

What is problem if we use larger CAP like 470nF?    

For CAC-USB1 AC-coupling capacitor (75 nF to 265 nF). this is part of the USB spec.

For CAC-USB2 AC-coupling capacitor (297 nF to 363 nF), please see attached ECN

7268.USB 3.1 ECN Rx AC Coupling Capacitor Option.pdf

Thanks

David

Hi Mochizuki,

I ran a USB compliance test on the EVM and got the following passing report:

USB 3.2 TX Compliance.pdf

Let me know if you have any questions.

Best,

Shane