Hi, Le Saturday 10 July 2010 22:02:37, Sébastien Bourdeauducq a écrit : > Hi, > > I have tested the two boards that I have received from Adam today, with the > video input patched (P[15:8] connected instead of P[7:0], and P[7:0] > disconnected by lifting the pins). > > It did not go well. Upon powering up the boards without a bitstream loaded > (FPGA idle with pre-configuration weak pull-up resistors on all I/Os) the > current was at the usual value (0.6A). Then, after about 30s it jumped to > more than 1A with a short circuit to ground appearing on the 3.3V and 1.8V > supplies. Once the board developed the short circuits, they did not go > away by power-cycling the board and the 3.3V and 1.8V voltages could not > be restored. The problem was exactly the same on the two boards. > > The video input chip seems to be the cause of the problem - I have removed > it from one board which had developed the short circuits, and all the > voltages and currents went back to normal and the rest of the board works. > > I am quite puzzled about explaining the cause of this issue. Possible > tracks: * connecting P[15:8] to the weak pull up resistors of the FPGA > causes the video chip to fail and short circuit 3.3V and 1.8V to ground? > how come? * solder-related problems, e.g. tin whiskers? > * chip overheated during rework? > * bad/counterfeit chip installed? (like the IR sensors...)
How about a test-mode sequence of the video-chip that you enter because of its input states? (I did not look at its datasheet). -- Florian _______________________________________________ http://lists.milkymist.org/listinfo.cgi/devel-milkymist.org IRC: #milkym...@freenode Webchat: www.milkymist.org/irc.html Wiki: www.milkymist.org/wiki
