Hello, we've been having an ongoing issue with the FT601 wherein the chip randomly does not enumerate on power up. This occurs about every 10 or so power up cycles. The FT601 is connected to a CYUSB3314 hub on the same PCB as itself. The two parts are less than 2 inches apart. I've attached schematics for the interface between the two parts. There was a prior version of this board using a USB5744 hub instead of the CYUSB3314 hub but the FT601 also failed to enumerate reliably in that configuration also. There are two or three other devices on the USB hub aside from the FT601 but those always enumerate at power up without issue. I've reviewed power rail start up timing in relation to the FT601s reset signal and can see that the FT601 gets about 100 ms worth of reset after 3.3V / 2.5V / 1.0V stabilize. When I check the FT601s clock output I can see it is starting up but then shutting down. The same is true when viewing the crystal's pins. The clock runs for about 120 ms and then shuts down for 100 ms and then repeats. Previously asserting the FT601s reset alone was enough to get it to enumerate after a failed power up but it seems that solution isn't working on the present version of the PCB. As far as I can tell I've followed every recommendation in FTDI's PCB guidelines document as well as the data sheet for the part. Hopefully someone else has been through this already with the FT601 and can help out?
Thanks very much!
Rich