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TUSB1210 Register Clarification for VBUS

Noah Root
Prodigy 120 points
Other Parts Discussed in Thread: LM3525, TUSB1210, TUSB1211

Hello,

I am working on a USB host design using the TUSB1210. I have a few questions in regards to VBUS and registers within the TUSB1210. As the host, I am using an LM3525 to enable +5VDC on VBUS, and my design is matches Figure 10-1 from the TUSB1210 datasheet.

1. Is VBUS enabled via CPEN by TUSB1210 after reset? Or does that require a register write to enable the VBUS switch?

2. Bit 7 of the OTG_CTRL register (offset 0x0A) describes a feature to use an external VBUS over-current indicator. If I want to use this feature, how do I interface an external error flag signal to the TUSB1210?

3. How does the TUSB1210 report and handle an over-current or short circuit event? Does the component nominally sense the voltage level on the VBUS via the VBUS pin? The datasheet describes a comparator; is that part of the logic for over-current/short circuit detection?

Thanks,

Noah

  • 0
    TI__Mastermind 36085 points

    Hello Noah,

        We are reviewing your questions and we will reply tomorrow.

    Best regards,

    Diego.

  • 0
    TI__Mastermind 36085 points

    Hello Noah,

        I have an update for you but I will need more time to answer the questions 2 and 3.

        1)  You must set DRVVBUS and DRVVBUSEXTERNAL bits (OTG_CTRL register, bits 6 & 5) must be set to 1 in order to to set Pin17 (CPEN). Please notice that the reset value for both registers is 0.

    Best regards,

    Diego.

  • 0 in reply to Diego Cortes
    Prodigy 120 points

    Hi Diego,

    Thanks for the quick response to my first question; I really appreciate it. I look forward to hearing back about the other questions. If you need any clarification on my question, please let me know.

    Thanks,

    Noah

  • 0 in reply to Noah Root
    Intellectual 345 points

    Hi Naoh,

    Regarding 2nd Question,

    According to ULPI specification, pin for ExternalVbusIndicator is optional and TUSB1210 doesn't seem to have provided that pin. Hence you might not be able to connect Fault pin from Vbus switch directly to TUSB1210. So setting bit 7 in OTG control register for this PHY might not be useful.

    Sorry I am little bit busy but will try to come back day after tomorrow. Will see if I can explain above in better way.

    Regards,

    Bhaumik

  • 0 in reply to Bhaumik Darji
    Prodigy 120 points

    Bhaumik,

    Thank you for your response; that was my understanding of the component. I wanted to make sure I didn't miss anything in the datasheet in regards to a pin for the ExternalVbusIndicator.

    I am still interested to learn more about my third question about VBUS comparators and how they determine over-currents and/or short circuits on VBUS.

    Thanks,

    Noah

  • 0 in reply to Bhaumik Darji
    TI__Mastermind 36085 points

    Hello Noah,

        Indeed, what Bhaumik said is correct, the TUSB1210 does not have the external pin to sense any external overcurrent event (you can see this difference between the TUSB1210 and TUSB1211). By the way, I am still looking for information regarding the question 3.

    Best regards,

    Diego.

     

  • 0 in reply to Diego Cortes
    Intellectual 345 points

    Thank you Naoh and Diego.

    Here are my comments regarding 3rd Question:

    3. How does the TUSB1210 report and handle an over-current or short circuit event?
    According to me, TUSB1210 does not have logic to detect over-curent condition. And also as it does not have ExternalVbusIndicator pin, it will not be able to report same.

    Does the component nominally sense the voltage level on the VBUS via the VBUS pin? The datasheet describes a comparator; is that part of the logic for over-current/short circuit detection?

    Yes, it senses voltage level on VBUS via VBUS pin. TUSB1210 contains Voltage comparators to report vbus status via RXCMD. Hence those comparators might not be able to sense over-current.

    If you wish to provide mechanism to turn off power when over-current is detected, you will need to route Fault signal of your Vbus switch to your FPGA and based on that you should design logic to disable CPEN pin by updating OTG control register ( clearing DrvVbus and DrvVbusExternal bits ).

    By the way, ISP1504 (PHY chip from NXP) supports Fault pin. Please have a look at it. It might help to get more information regarding over-current event.

    If any of you find some more information, please share.

    Kind Regards,

    Bhaumik

  • 0 in reply to Bhaumik Darji
    Prodigy 120 points

    Thank you for the help, Diego and Bhaumik. I have a much better understanding now for how to implement the TUSB1210 and VBUS.

    Thanks,

    Noah