Hello,
I've got a catch 22 with some ESD diodes I added to the USB lines. I have used the NUP2201 and tied the USB_DP and USB_DM lines from VBUS to GND. I used a separate NUP2201 to tie the USB_ID to 3.3V.
The problem I have is that when the unit is connected and running in device mode, then later disconnected, the disconnect is not recognized. The reason is that the VBUS line is not dropping after the disconnect below ~2.7V. It turns out, the reason for this is that D+ is high before the host disconnects, so when the host disconnects and VBUS is supposed to discharge, D+ can instead supply current to the VBUS line through the ESD diode, so the unit never realizes the device has disconnected. The D+ line doesn't have anywhere to discharge when is OTG mode
The unit still operates when a cable is again plugged in, device or host, but I need to be able to detect a disconnect.
It seems this would be standard practice for protect the OTG lines via ESD diodes, am I missing something??
If I remove the external ESD diodes, what kind of protection do I have on the USB_DP and USB_DM lines in the chip?
Thanks,
Mike
