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TUSB4020BI-Q1: TUSB4020BI-Q1

Hsun-Tsan Shen
Prodigy 10 points
Part Number: TUSB4020BI-Q1

We have made 10 circuit cards, 2 of which are fully functional, and when the other 8 are connected to the computer, the computer often cannot scan and find that the TUSB4020BI-Q1 has been inserted into the USB port, and often have to be plugged and unplugged many times , because the circuit design is wrong where?

  • 0
    TI__Guru**** 152496 points

    Hi,

    It looks like the SMBUSz is pulled low from the schematic. With SMBUSz being pulled low, you are in SMBUS mode. The TUSB4020BI-Q1 waits indefinitely for configuration by the SMBus host and does not connect on the upstream port until the SMBus host indicates configuration is complete by clearing the CFG_ACTIVE bit.

    Can you please remove R100 and see if you are able to get the hub to work?

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    Prodigy 10 points

    Thank you for your reminder. After the modification, most of them work normally, only one piece occasionally fails to identify the device (USB Device Not Recognized), do you need to add a boost resistor, or it is better to leave it blank and not connect the resistor!

  • 0 in reply to Hsun-Tsan Shen
    TI__Guru**** 152496 points

    Hi,

    For USB_R1, below is the recommended resistor value. 

    • MAX: 10.85- kΩ ±1% • TYP (Recommended): 9.53-kΩ ±1% • MIN: 8.25-kΩ ±1%

    Changing the value of this resistor adjusts the output driver strength for USB 2.0 Highspeed transmitters. Increasing the value of this resistor decreases the output driver strength for USB 2.0 High-speed transmitters, decreasing eye height. Decreasing the value of this resistor increases the output driver strength for USB 2.0 High-speed transmitters, increasing eye height.

    Have you done USB2.0 compliance test on the TUSB4020B downstream ports?

    Thanks

    David