USB host without VBUS and DRVVBUS

jcm

Is it possible to use the AM335x USB ports in host mode without connecting VBUS or DRVVBUS?

From other things I have read on these forums (e.g. http://e2e.ti.com/support/dsp/sitara_arm174_microprocessors/f/791/t/197987.aspx) I suspect not, but I'd appreciate a categorical answer.

Thanks,

Jonathan

over 11 years ago

0 peaves over 11 years ago

TI__Guru 59125 points

No.

The OTG controller monitors the voltage on VBUS and expects a valid VBUS voltage when DRVVBUS is active and does not expect a voltage potential on VBUS when DRVVBUS is not active.

You should use a current limited power switch to control VBUS with the active high enable connected to DRVVBUS.

Regards,
Paul

0 jcm over 11 years ago in reply to peaves

Prodigy 210 points

Thanks Paul.

It is a bit tedious we have to route two extra lines and add another chip when what we want is a simple USB host attached to a hub.

0 Saravanan Karivandan1 over 10 years ago in reply to peaves

Prodigy 165 points

Dear Paul,

You should use a current limited power switch to control VBUS with the active high enable connected to DRVVBUS.

In this case where this USB0_VBUS pin should be connected. Whether this has to be connected to power switch output or USB connector alone or both??

Regards,

Saravanan.K

0 -DK- over 10 years ago in reply to Saravanan Karivandan1

TI__Mastermind 27890 points

In the case of a Host implementation, the USBn_DRVVBUS-controlled power switch output should be connected to both the USB connector and the USBn_VBUS pin.

0 Tim Chao Li over 10 years ago in reply to -DK-

TI__Expert 4415 points

Hi all,

In the case that the AM335x USB controller is always in host mode and the peripheral IC is powered separately (so negligible current draw), is there any reason using a logic gate to drive USB_VBUS high wouldn't work? What are the benefits of using a power switch IC to drive VBUS?

Thanks!

0 peaves over 10 years ago in reply to Tim Chao Li

TI__Guru 59125 points

You may find a circuit similar to one shown below can be used for this use case.

Note: The AM335x VBUS terminal must be greater than 4.4 volts for it to consider VBUS valid.

Regards,
Paul

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USB host without VBUS and DRVVBUS