Powering XEM3005 using external 3.3V and 1.2V supplies

Spartan-3 USB 2.0 Modules
1

I connected 3.3V and 1.2V from my on-board power suppleis to JP3 pins 5,7,9,11 and to 6,8,10,12 respectively. I also provide 3.3 to JP4 pin 41,42 and disconnected the FB2 on the XEM3005 board.
My problem is that when I connect the USB cable the USB supply takes over and there is contention between my external supply and the USB power
How I can disable the USB power so that I can power the XEM3005 from my supply exclusively
Thanks Ehud

2

Ehud–

USB power (+5VDD) is not connected to any supply on the XEM3005. It is only connected to the +VDC pins on the expansion bus.

To be clear, the +5VUSB net is only attached to 3 locations:

  1. P1-1 (pin 1 on P1, the USB connector)
  2. JP3-3
  3. The thru-hole pad marked “+5VUSB”

So where are you seeing contention?

Opal Kelly Support

3

I guess I am missing something. Let me look more carefully on what is going on.
Ehud

4

Hi
How to me to connect XEM3005 to the external power supply not using BRK3005?

5

@duda283-- Please refer to the XEM3005 User’s Manual for the expansion bus pinout. The section titled “Power Supply” of the manual indicates that

— Begin quote from ____

“Power must be provided as well-regulated 3.3v and 1.2v DC supplies and can be delivered via the expansion connectors or using the 0.1”-spaced power header"

— End quote