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TUSB2077A: USB devices can't be recognized on the PC side.

zhang ping
Genius 3835 points
Part Number: TUSB2077A

The following is my application system diagram, and the attachment is the datasheet of ft4222: tusb2077a No.2 can't read the downstream devices when it runs for 10 to 20 hours, and USB devices can't be recognized on the PC side. Tusb2077a No.1 and No.3 occasionally appear. At this time, the power on restart system sometimes recovers, sometimes it can't recover, and the hubgfg / portpwr / portdis LED displays red.

Question 1: ft4222 is 3.3V, and VBUS is connected to 5V. At this time, does the VBUS of ft4222 need 22uF capacitor? Is 22uF capacitor required for 3.3V VCC?

2. The power supply mode is as shown in the figure. A 3.3V 3A DC / DC output supplies all 3.3V power supply, and a 5V 3A DC / DC supplies 20 ft4222 VBUS. Is there any problem with the power supply mode?

3. The reset time of tusb2077a is more than 1ms when I connect RC. Is there any problem with reset mode? Is reset time OK?

4. The first stage of tusb2077a uses three ports and the other four ports are NC. The second stage of tusb2077a uses six ports and the other one is NC. Is there any problem with the design?

5. Is there any special regulation on power sequence of tusb2077a and downstream equipment, can power on simultaneously?

6、 A 30ohm resistor is connected in series on dm1-dm7 / dp1-dp7, and a 30ohm resistor is also connected in series on DM / DP of lower level equipment, as shown in the figure. Can both of them exist at the same time? 

 

DS_FT4222H.pdf

2843.TUSB2077A_SCH.pdf

  • 0
    TI__Guru 60870 points

    HI Zhang,

    1. / 2. We cannot comment on the FTDI device requirements.

    Can you confirm that VBUS is staying stable during the test?  Do all device stay responsive for 10-12 hours before failing?  

    3. Reset timing would not cause an issue after the system has been actively running for hours, a reset issue would appear during the initial connection.

    4.  As long as the system has adequate power, this bus structure is not an issue.

    5. Are you seeing issues during power on or only after the system has been powered?  How is the current system powered: hubs first or device first?

    6. Yes, both sets of resistors can be on the bus simultaneously.  The 1.5K pullup should be next to the hub however, not on the other side of the series resistor.

    Regards,

    JMMN