VBUS error workaround (delay coming)

Shinu Mary Varghese

Other Parts Discussed in Thread: AM3354

Hi,

I am working on Am3354 based custom board.

If i connect pendrive to USB host port its detecting. But if i connect some other pendrive to the USB host port its showing "ti81xx_interrupt 1146: VBUS error workaround (delay coming)" error. It will work if i plugged in on boot and will not to hot-plug. I checked VBUS, it's stable on 5V.

Any idea?

Thanks

over 11 years ago

0 Biser Gatchev-XID over 11 years ago

TI__Guru**** 393215 points

Hi Shinu,

First of all the 22Ohm resistors you have on the USB data lines must be removed. They will compromise signal integrity. Second, you have not implemented a VBUS power switch. The USB PHY needs to drive a power switch in Host mode. When a USB device is plugged in the PHY drives USBx_DRVVBUS high, and a valid level on USBx_VBUS is expected after that happens. Your design has +5V always present on USBx_VBUS pin.

0 Shinu Mary Varghese over 11 years ago in reply to Biser Gatchev-XID

Intellectual 965 points

Hi Biser,

We have same connection in carrier board too.

No errors are getting in that carrier board.

Thanks

0 Biser Gatchev-XID over 11 years ago in reply to Shinu Mary Varghese

TI__Guru**** 393215 points

Are you using exactly the same software?

0 Shinu Mary Varghese over 11 years ago in reply to Biser Gatchev-XID

Intellectual 965 points

yes same software i am using

0 Biser Gatchev-XID over 11 years ago in reply to Shinu Mary Varghese

TI__Guru**** 393215 points

Is this Linux? What version?

0 Shinu Mary Varghese over 11 years ago in reply to Biser Gatchev-XID

Intellectual 965 points

Yes its linux 3.2.0.

0 Biser Gatchev-XID over 11 years ago in reply to Shinu Mary Varghese

TI__Guru**** 393215 points

Hi Shinu,

Another observation made by the factory team: There is no capacitor on VBUS next to the USB connector. This could be very likely the root issue for this error.

For Host mode you must have >120uF on VBUS next to the USB connector.

0 Biser Gatchev-XID over 11 years ago in reply to Biser Gatchev-XID

TI__Guru**** 393215 points

Recommendation is to check for a voltage drop on VBUS with an oscilloscope.

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VBUS error workaround (delay coming)