TUSB4020BI-Q1: probabilistic communication failure

Hi Junlong:

     Power on sequence looks good, what is supply ramp rate?

    Also please check if crystal is oscillating when it failed.

Regards

Brian

Hi Brian,

    The crystal oscillator appears to work when communication fails.

Hi Brian,

    This is supply ramp rate when communication fails.

Hi Junlong:

      Power sequence looks good to me. What is the failure ? Can you send schematic for review?

Regards

Brian

Hi Brian:

    When the MCU is powered on, using the 'lsusb' command, sometimes the chip is recognized, sometimes it is not.

Hi Junlong::

   From schematic , it seems the voltage after divider is 0.4v? It should be 0.5V after divider, you need to remove 20k on Vbus.

Regards

brian

目前我们测试4块板子，我们单片机(S32G274A)在断开EEPROM(断开SCL和SDA)的情况下可以与USB HUB(TUSB4020BI-Q1)一般可以正常通讯，2个PORT口均能正常通讯。但现在4块板子，都存在共性问题：单片机上电后经常识别不到USB HUB

Hub can work without EEPROM, did customer need to change configuration with EEPROM?

Regards

brian

 This 22pin(Vbus,USB83340AM) is input pin, not output pin. VBUS voltage is 5V.

What is relationship between  EEPROM and S32G274A ? We may need to have a call.

Regards

Brian

I already sent you my phone number in a private message.

got it, waiting for your update.

Regards

brian

Hi Brian,

    Sorry for the late reply.

    We have confirmed that the abnormality is caused by a small probability of affecting the power-on timing of TUSB4020BI during the power-on process of some devices.