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TPS2553D: Current distribution/sharing between ports in actively powered USB hub

Petr Senfluk
Prodigy 10 points
Part Number: TPS2553D

Hello,
I am designing USB hubs with USB2517 (6 port) and USB5806C (6 port). Hubs are actively powered and part of the carrier board for SMARC SOM computer.

My question is about 5V PSU current capability requirements and USB compliancy. Theoretically I would need 6 x 0.5A + 6x 0.9A, that is 5V / 8.4A total. But, this power will never be used in end user application. End user will use low power USB devices in 50% of ports.

Must each port be able to provide its nominal current (0.5A for USB 2.0 and 0.9A for USB 3.2) at the same time?

Can we use shared power resources (for example 5V/0.6A for 2x USB 2.0 ports with /OVER_CURRENT feedback connected to USB hub) were each port will have also its own 0.5A current limitation with /OVER_CURRENT feedback connected to hub?
Each port would be able to provide 0.5A current, if current consumption from the other port is below 0.1A. And, total current requirement for both ports would be only 0.6A instead of typical 1A.

Same question about USB 3.2 ports. Just different port current values.

Can we use shared power resources (for example 5V/1.05A for 2x USB 3.2 ports with /OVER_CURRENT feedback connected to USB hub) were each port will have also its own 0.9A current limitation with /OVER_CURRENT feedback connected to hub?
Each port would be able to provide 0.9A current, if current consumption from the other port is below 0.15A. And, total current requirement for both ports would be only 1.05A instead of typical 1.8A.

Thank you,
Petr Senfluk
Senior HW Engineer
SAWtronics s.r.o.

  • +1
    TI__Mastermind 29440 points

    Hi Petr,

    What you are describing doing is not technically allowed to be perfectly compliant; however, what you are describing will work in almost any real system.

    Most compliance testers would not even catch that you are out of compliance because they typically test 1 port at a time and your plan would pass in this case.

    As long as your customer(s) understand that they may need to shift their cables around to make power work for the system, then I do not see any issue with what you are proposing.

    Regards,

    Chuck