AM3352: USB VBUS sensing interval

Takahiro Ogo

Part Number: AM3352

Hi,

I have some questions about USB VBUS sensing of AM335x.
My customer is feeling that AM335x USB VBUS error is late.

So, I want to confirm about the follows.
1) Is there VBUS sensing interval? If yes, what time is the VBUS seining interval?
2) When VBUS falls below 4.4V, how long does it take to become VBUS error?

Best Regards,

Takahiro Ogo

over 8 years ago

0 Biser Gatchev-XID over 8 years ago

TI__Guru**** 393215 points

Hi,

1. The USB PHY would continually monitor the voltage on the VBUS and report the status to USB controller.
2. Upon the USB controller determining its role as a host, it will drive the USBx_DRVVBUS pin high to enable the external power logic so that it start sourcing the required 5V power (must be ≥ 4.4V but to account for the voltage drop on the cable it is suggested to be in the neighborhood of 4.75V). The USB2.0 controller will then wait to for the voltage of the USBx_VBUSIN to go high. After 100 ms, if it does not see the voltage on the USBx_VBUS pin to be within a Vbus Valid range (>= 4.4V), it will generate a VBUS error interrupt.

0 Takahiro Ogo over 8 years ago in reply to Biser Gatchev-XID

Genius 5940 points

Hi Biser,

Yeah, I already know that.
What I want to know is the interval time monitoring VBUS during USB normal operation. (it is not the VBUS start-up)

Best Regards,
Takahiro Ogo

0 Biser Gatchev-XID over 8 years ago in reply to Takahiro Ogo

TI__Guru**** 393215 points

The USB PHY would continually monitor the voltage on the VBUS and report the status to USB controller.

0 Takahiro Ogo over 8 years ago in reply to Biser Gatchev-XID

Genius 5940 points

OK....When VBUS falls below 4.4V, how long does it take to become VBUS error?
Do you have such a data?

Taka

0 -DK- over 8 years ago in reply to Takahiro Ogo

TI__Mastermind 27890 points

Taka-san,
This value is not characterized. The USB PHY's internal comparator signals the state of VBUSVALID via the UTMI+ bus directly to the USB controller.

0 Takahiro Ogo over 8 years ago in reply to -DK-

Genius 5940 points

Hi DK-san,

Thank you for your reply.
I understood this situation. OK, I will tell that to my customer for now.

Best Regards,
Taka

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AM3352: USB VBUS sensing interval