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ISOUSB211: The USB device is not detected by the PC approximately every third time it is connected.

SANATH kumar
Prodigy 60 points
Part Number: ISOUSB211

Tool/software:

Hello,

We are using the ISOUSB211 in our design to isolate USB lines. 

The upstream-facing port (Side 1) connects to a PC via a USB connector, and the downstream-facing port (Side 2) is always connected to a processor module (i.MX).

Observations:

  • The USB device is not detected by the PC approximately every third time it is connected.
  • In this case Side 1 D+ line on Side 1 stays at around 1.8V.
  • In this state, Side 2 draws ~104 mA @ 3.3V. else Side 2 draws ~84–86 mA.

Power Configuration:

Side 1 (Upstream - PC Side):

  • Powered via 5V from the PC USB port.
  • 5V is connected to both VBUS and VCC1.
  • Internal LDOs generate 3.3V and 1.8V.
  • CDPEZ1 is pulled up.

Side 2 (Downstream - i.MX Side):

  • Always powered up via 3.3V from the device.
  • 3.3V is connected to VBUS, V3P3V2, and VCC2.
  • Internal LDO generates 1.8V.
  • V1OK is connected to the i.MX for USB connection detection.
  • CDPEZ2 is pulled up.
  1. Is it acceptable for Side 2 to remain powered up always?

Regards,

SANATHKUMAR

  • 0
    TI__Guru 55795 points

    Hi Sanath,

    Thank you for reaching out.

    The power configurations you have mentioned look good. Please do share the schematic so that we can review to check everything is okay in schematic.
    May I know if this testing is done using ISOUSB211DPEVM or if this is done on your own PCB? If this is your own PCB, can you please confirm if you see this issue on only one PCB or does it happen on multiple PCBs?

    Can you please also share a picture of device top marking to make sure this is not pre-production material?


    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    Prodigy 60 points

    Hi Koteshwar Rao

    The test has been conducted on ISOUSB211DPEVM and only we have given power supply as mentioned previously.

    Regards,

    SANATHKUMAR

     

  • 0 in reply to SANATH kumar
    TI__Expert 7325 points

    Hi Sanath,

    Thanks for conforming the hardware setup to the EVM. 

    Koteshwar Rao said:
    Can you please also share a picture of device top marking to make sure this is not pre-production material?

    Could you please provide this input in order for us review further.

    SANATH kumar said:
    Always powered up via 3.3V from the device.

    You used the onboard 3.3V LDO supply or is it a supply from the i.MX module? If it is the later, can you please check with onboard LDO 3.3V Supply and see if the issue persists.

    Regards
    Varun

  • 0 in reply to Varun Kumar
    Prodigy 60 points

    hi,

    sharing you the details

     picture of device top marking 

    full setup

  • 0 in reply to SANATH kumar
    TI__Guru 55795 points

    Hi Sanath,

    Thank you for sharing the requested images.
    Could you please try ordering new samples from TI website and test them by placing them onto your EVM and connecting it to your processor?

    I also see that you have used some wires to convert the EVM Type A port to Type C. Instead, can you use Type A to Type C adapters so that we can eliminate any possibility of issues due to wiring?


    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    Prodigy 60 points

    hi koteshwar,

    we will try to build our circuit as per your suggestion and let u know the result.

    regards,

    sanathkumar