66AK2G12: Keystone 2 unused USB pins

Avner Cohen

Part Number: 66AK2G12

I am using the 66ak2g12. But the USB is not used at all.

Can you please confirm the pins in the list to be float or short or pulled down to GND as described in the attached table (see notes in red):

I seek to make the card reduced noise as I can. Is it possible to short to GND B19, A21 (VBUS)?
It was written in the forum that the USB0_TXRTUNE_RKELVIN, pins C19 and C20 to have the 200 Ohm resistor. can that be avoided if the USB is not used at all ?

Thanks,

Avner

over 4 years ago

0 peaves over 4 years ago

TI__Guru 62855 points

I do not understand your concern related to noise on VBUS. There should not be any issue leaving VBUS unconnected when not used. It is very unlikely VBUS will encounter enough noise to cause a problem if you are not connecting a signal trace. The typical use case supports connecting this pin to an un-terminated USB connector and we are not aware of any noise issues resulting from this use case.

I'm still checking on the requirement to connect a resistor to the respective RKELVIN pin. However, I'm fairly sure a resistor is needed even when the port is not used.

Regards,
Paul

0 peaves over 4 years ago in reply to peaves

TI__Guru 62855 points

I have confirmed you should leave VBUS unconnected when not used.

Each USBx_TXRTUNE_RKELVIN pin should have a 200 ohm resistor connected between it and VSS even when the respective USB port is not used.

Regards,
Paul

0 Avner Cohen over 4 years ago

Intellectual 460 points

Thank you very much. Closing case.

Avner

0 Avner Cohen over 4 years ago in reply to Avner Cohen

Intellectual 460 points

Thank you very much.

Closing case.

Avner

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66AK2G12: Keystone 2 unused USB pins