TUSB522P: AC coupling location of TUSB522P

user4943534

Prodigy 50 points

Part Number: TUSB522P

Hi Everyone,

In TUSB522P datasheet page 1, simple schematic put the ac coupling caps close to TX output.

But in TUSB522P datasheet page 14, layout guideline ask to must put ac coupling caps close to connector.

It means put ac coupling caps close to USB device and far away TX of TUSB522P.

May I know which one is correct? close to TX or far away TX?

Also need to confirm how to place ac caps on HOST to TUSB522P.

Thanks

Allen

over 6 years ago

0 David (ASIC) Liu over 6 years ago

TI__Guru**** 181321 points

Allen

The placement of the DC blocking capacitors is not critical, but more important is in choosing the correct value and minimum body size will minimize any impedance discontinuities in the signal path.

Thanks

David

0 user4943534 over 6 years ago in reply to David (ASIC) Liu

Prodigy 50 points

Thanks David,

TI suggest 100nF for TUSB522. Does any calculate tool for value?

We also need to know which location is correct.

Thanks

Allen

0 David (ASIC) Liu over 6 years ago in reply to user4943534

TI__Guru**** 181321 points

Allen

The capacitance requirement comes from the USB spec.

Cac-coupling min is 75nF and max is 265nF. All Transmitters shall be AC coupled. The AC coupling is required either within the media or within the transmitting

component itself.

Crx-ac-coupling min is 297nF and max is 363nF. Receivers may be AC coupled if desired. If used, the AC coupling is required to be either within the media or within the receiving component.

The location of the capacitor is not critical.

Thanks

David

0 Malik Barton57 over 6 years ago in reply to user4943534

TI__Guru 64326 points

Hi,

If by location you are referring to placing the AC caps in between the USB Host and redriver or USB connector or redriver, please refer to Figure 2. Embedded Host Application in the TUSB522P datasheet.

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TUSB522P: AC coupling location of TUSB522P