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TUSB4020BI: crystal not oscillating

TS Yang
Genius 4800 points
Part Number: TUSB4020BI

Hi,

I'd like to use TI's USB4020BI USB 2.0 hub for my application.

But the Oscillator connected to XI / XO does not work.

Are there any special sequences to operate this device? It was not found in the datasheet.

The schematic of our board will be attached.
Please check if there is a problem.
2308.USB_HUB.pdf

One peculiarity is the Power-Up Timing Requirements in figure1 of the TUSB4020BI datasheet.
In our board, VDD is enabled before VDD33. Is this sequence causing the crystal and related blocks not to work?

thanks,

TS

  • 0
    TI__Expert 7395 points
    Hello TS,

    Crystal requirements are detailed on section 9.1.1 of the datasheet. I would recommend you to check that the selected crystal complies with those specs, other than that, the part of the schematic you shared looks good to me. Just notice that you are configuring the device in SMBus mode, so the device will not enumerate until the CFG_ACTIVE bit is cleared by the SMBus master (this won't impact crystal oscillation though)

    Additionally I would recommend to x-ray your board to verify proper soldering on the thermal pad; being the only ground terminal on the device, poor soldering may lead to device issues.

    Regards,
    Jorge