• State TI Thinks Resolved
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 15 subscribers
  • Views 215 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ISOUSB211: USB Isolation and disabling 480M Mode in Tiny USB

Andrew Kirby1
Prodigy 185 points
Part Number: ISOUSB211
Other Parts Discussed in Thread: AM2434, , ISOUSB111

Looking at implementing USB Isolation between an AM2434 (ALX) as a peripheral role and a USB2.0 connector.

Currently the part of choice is the TI ISOUSB211

It seems from the ISOUSB211 datasheet Figure 10.2 that the EQ configuration on peripheral application has a higher gain set on the MCU side than the connector side.

Q: I would have thought that the connector/cable end would need more gain than the couple of inches of track to the MCU. Why is this not the case here?

Q: The EQ setting is fixed, not dynamic. So how do you deal with different USB Cables?

Q: Given the LP-AM243X and its Tiny USB SDK as a starting point, if we wanted to remove the 480M capability so we can use a ISOUSB111 without 480M Support what is the right way to switch this off in firmware? (We don't really want to make a modified copy of the TinyUSB code and have to maintain it)

Thanks

Andy

  • 0
    TI__Guru 53095 points

    Hi Andrew,

    Thanks for reaching out.

    Please note that the EQ setting used in example block diagrams are only examples, you can choose them according to your application needs. Please see my inputs below to all the 3 questions you listed out.

    1. Please note that the EQ setting is compensate for the insertion loss created due to traces on PCB on either side of ISOUSB211 device and not for cable loss. The loss due to cable is already included in USB specification and hence, that is already accounted for while the losses due to PCB traces, especially when they are long, need to be addressed to meet USB specifications at the connector.
      1. It is also a common recommendation and desirable to keep the ISOUSB device closer to connector. while keeping the MCU / MPU also as close as possible. This makes the compensation needed on connector side to be lower than that needed on MCU / MPU side.
      2. This is the reason why you see we choose lower settings on connector side and higher settings for MCU / MPU side as an example.
    2. As stated in the previous point, the EQ setting is for compensating for the PCB traces which are going to be fixed during PCB design phase. Hence, the EQ settings don't need to be change dynamically once PCB design is frozen.
    3. Your understanding is correct, ISOUSB111 can be used for applications that only require LS (1.5Mbps) and FS (12Mbps).
      1. Regarding your question related to the firmware in AM243x, please post your question in MCU forum so that you get the most accurate answer to your question. I am listing below the direct link to the forum for AM243x. Thanks.
        1. https://e2e.ti.com/support/microcontrollers/arm-based-microcontrollers-group/arm-based-microcontrollers/f/arm-based-microcontrollers-forum


    Regards,
    Koteshwar Rao