Tool/software:
I am using the TUSB2046I USB hub IC in my design with three downstream ports connected to USB-to-UART converters. While the 1st and 2nd downstream ports function correctly and enumerate as COM ports on the host system, the 3rd downstream port is not detected or functional. And all OVRCURx pins are connected to 3.3V using 10kΩ pull-up resistors. The hub is operating in bus-powered mode with a stable 3.3V supply, and the RESET signal is properly pulsed during power-up. The PWRON3 pin shows approximately -45mV, indicating the hub is not enabling the 3rd downstream port, and the VBUS on the 3rd port remains at 0V. USB differential signals DP3 and DM3 are properly connected and exhibit no shorts or interruptions, but no signaling activity is observed when a device is connected. Despite these issues, the hub is recognized correctly by the host, and downstream ports 1 and 2 enumerate as expected. I have tested with simpler USB devices like flash drives on the 3rd port, swapped USB-to-UART converters between ports, and even bypassed the USB connector to connect a device directly to the hub IC's DP3 and DM3 lines, but the 3rd port still fails to function. I have also inspected the hub's configuration using USBView, which only lists two downstream ports. Could this issue be due to an internal IC fault, a configuration oversight, or something else I may have missed? Any recommendations for further diagnostics or solutions would be greatly appreciated.
