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LS1046A USB Controller VBUS requirements

Question asked by Joshua Tyler on Jun 18, 2020
Latest reply on Jun 18, 2020 by ufedor

Hi,

 

I'm currently designing a PCB using an LS1046A, and wish to use the USB controllers.

 

I'm trying to figure out how to connect the VBUS pins on the controllers.The devices I am communicating with do not require a VBUS connection, just the data lines. I also do not have a 5V supply currently on my PCB, so I would have to place down a supply just for this VBUS connection. It seems unusual that a 5V supply is required in addition to the 3V3 and 1V0 USB supplies.

 

I think that connection is required but I can't find much documentation on this. The datasheet doesn't give requirements for the VBUS pins. AN5252 Table 22 says that connection is compulsory and the pins have a voltage range of "0-5.25V", but does not give an estimated current draw.

 

The LS1046ARDB schematic appears to connect the USB_3 VBUS to USB_P2_PWR, but this net is not powered (pin C1 of U3 is tied low). Does this mean that the USB3 bus is non functional on LS1046ARDB?

 

Are the VBUS pins compulsory for operation of the USB busses? if so, how much current do they draw? And are there any sequencing requirements for this power supply?

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