TUSB8040A LFPS Detection

1859464

Other Parts Discussed in Thread: TUSB8040A

Hello,

On any given US or DS port of the TUSB8040A hub, is the LFPS detection circuit first filtered by a low-pass-filter? I.e. Can a signal that is higher than allowable LFPS frequency (higher than 50MHz) trigger a U3 wake-up? Other than the amplitude, what metrics does the TUSB8040A enforce on the received LFPS signal to determine if it is valid LFPS or invalid LFPS, with regards to a U3 wake-up?

Thanks,

over 8 years ago

0 Elias Villegas M. over 8 years ago

TI__Guru* 76130 points

Hello,
The period of a LFPS signal is specified to be 20ns-to-100ns
Every LFPS "command" is defined with a different burst time, this is what triggers each specific action.
Regards

0 1859464 over 8 years ago in reply to Elias Villegas M.

Intellectual 575 points

Hello,
Those specs are generally for the generation/transmission of LFPS as per the USB 3.x spec. My question is how does the TUSB8040A police received LFPS to determine if it is valid or not. For example, if the TUSB8040A's link partner transmits LFPS at 100MHz (over double the spec allowed LFPS frequency), does the TUSB8040A reject/ignore that LFPS when the TUSB8040A is in U3 suspend state?
Regards,
KT

0 Elias Villegas M. over 8 years ago in reply to 1859464

TI__Guru* 76130 points

Hello,

The specification does not require to ignore LFPS> the maximum frequency, the hub does nothing to ignore those signals.

Regards

0 1859464 over 8 years ago in reply to Elias Villegas M.

Intellectual 575 points

Hello,
Our interest is not that TI guarantees TUSB8040A operation outside specification, but rather that the TUSB8040A will prevent/ignore LFPS signals that are outside specification. Does the TUSB8040A do that in any way?
Regards,
Kris

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TUSB8040A LFPS Detection