~27 days ago I bought the saturn LX45 board (several of them). Today one only emits a high pitched whining sound coming from the LX45 chip regardless of what .bin I load onto it. UPDATE 1: I replaced the USB cable and the device now works normally. UPDATE 2: The unit keeps burning up USB cables. UPDATE 3: The unit no longer lights up and get's extremely hot and emits an odor. UPDATE 4: I have concluded that this unit is burned up.
Hi connorj, Thanks for reporting this incident. Can you please confirm if there was any short circuit or placed the board on something metallic (like pieces of wire or tools) even for a moment? ICs burning up spontaneously while connected to USB highly unlikely because USB port because the voltage never exceeds 5V (usual culprit behind spontaneous burns are power surges, which shouldn't happen on USB). Thanks, Tom
Tom, My FPGA's are all secured in Acrylic so there is no way to accidentally cause a short on the board. That said I do not use USB to power the boards, instead I use these: http://www.newegg.com/Product/Product.aspx?Item=N82E16817153145 These power supplies will shutdown with any type of short or abnormality in current flow in less than 1/100 of one second much like a GFCI(1/20 of one second), which I also use at the wall as an additional defense. The problem I see with the boards is that the USB is still drawing power even with the Jumper for external power enabled because when I shut off the ATX power supply the Saturn's Heatsink Fans KEEP RUNNING from USB power. This is IMHO what has been causing the failure of the USB cables. What I do not understand is why with the jumper set there would be any power going to the board at all much less the fan that is drawing it's power from the board itself. To prevent this situation, I must first unplug the USB cables from the host system and then shutdown the power to the Saturns via the ATX. If you do not then the host computer will detect a short and it's ThermalTake will kill the power. Also the host computer will NOT power up without the FPGA ATX powered on because it shuts down by detecting a short from the USB going to the Saturns. I can repeat this and burn up USB cables while the MojoV3 boards attached to the same host have zero problems but they also do not have jumpers for external power as it's handled "on the board" automatically. I am reviewing the Saturn board schematics to see if I can find the problem as to why when using external power and shutting it down the boards keep powering it's fan. Some of my other FPGA's (ZTEX) that use external power use TWO ground wires from the ATX to prevent USB power fluctuations from damaging the board and they explicitly warn about this. Thanks
Thanks, that makes sense for sure. PC power supply has enough oomph to burn a board, which USB power lacks. Anyway, we reviewed the schematics and board thoroughly and didn't see anything wrong at all. If the jumpers are placed correctly, there shouldn't be any connection between external power and USB power. I have copied the relevant sections of the schematics and boar layout. Please see below. USB VBUS goes straight to the jumper and as long as there is no jumper, its essentially unconnected. Better than diode for sure. Thanks, Tom
