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HD3SS3220: Section 8.2.4.1 VBUS used to Power VDD5. What if VBUS falls below 4.5V?

Peter Bouvy
Prodigy 140 points
Part Number: HD3SS3220

Dear Team,

In section 8.2.4.1 the datasheet suggests that for a UFP design VBUS can be used to power VDD5.

The HD3SS3220 datasheet also presents the following recommended operating conditions for the devices 5V power supply.

VDD5 5-V Supply Voltage Range 4.5 to 5.5V

VBUS 4 to 28V

From my understanding of the USB Type-C specification 4.00V is the minimum VBUS voltage that can be seen by the sink after voltage drop through a type-c cable and set of mated connectors.

This appears to be reflected in the recommended operating condition for VBUS provided by the datasheet (4 to 28V).

The device I am designing will pull over 2A and at times the VBUS seen by the HD3SS3220 may fall below 4.5V due to losses in the cable and connectors. 

My question is if VBUS is used to power VDD5 and it drops below 4.5V will the HD3SS3220 device still operate correctly? 

Thank you in advance for your help.

Kind Regards,

Peter Bouvy

  • 0
    TI__Guru 64326 points

    Hi Peter,

    When VDD5 is under 4.5V HD3SS3220 will not operate correctly. VDD5 can be powered from Vbus but only in applications where the 5V Vbus is guaranteed. Typically in Vbus will never increase over 5V unless PD controllers are used on either end. Is it possible for you to use a separate 5V supply?