Xilinx DCM Shuts down at 75degree centigrade

The temperature range is for die temperature usually. How and where are you measuring the temperature?

With internal logic running at 155MHz (at least the clock section) a

Alternaltively (and I admit to not having looked closely at the data sheet), the temperature may be for ambient, but one has to be very careful - the power dissipation ratings get derated above a certain temperature, which may be 70C, but is more commonly device dependent. When a manufacturer states their device will work in ambient temperatures of (for instance) 85C, they mean 'work at ambient temperatures of 85C with this [you have to work it out] maximum power dissipation.

The ultimate issue is always die temperature.

Cheers

PeteS

Debashish,

All Xilinx specifications are based on die temperature (junction temperature).

As long as the junction is below the specified temperature (85C for commercial, 100C for industrial), all specifications are met.

It sounds like your junction temperature is much higher than what you think it is.

How much power is your part dissipating?

What sort of heatsink is on it?

What is the airflow over the part (heatsink)?

Have you predicted the junction temperature from the above information (and what is the predicted value)?

Austin

A quick addition to the replies you've already received:-

Always route out on the PCB the connections to the on-chip temperature diode. DXN, DXP. That way you know what's going on, directly on the die. I suspect that the DCM isn't your problem, I've run parts near the temperature specs and occasionally beyond (when the fan broke!) and didn't have any problems with DCMs. Mind you, I do take great care of my Vccaux supply. HTH, Syms.

Ages ago, IC manufacturers used to specify a max ambient temperature (70 degr.C for commercial parts). We soon found out that this makes no sense for programmable parts. The FPGA manufacturer does not know what the user implements inside the chip (what clock frequency, what utilization) and how the chip is cooled. The only reasonable specification that we can guarantee is the max junction temperature. So we pioneered the Tj max 85 degr.C specification for all commercial parts. The user is the only person who then can evaluate whether the chip is operating within these guaranteed limits, and can modify the design or the cooling to bring it within specification. It would be nice if the FPGA-manufacturer could guarantee operation at a given ambient temperature, but that is inherently impossible, especially for parts where the user can program the logic and choose the clock speed. As a rule of thumb, no package without a heatsink has a thermal resistance (junction-to-ambient) below 10 degr.C per Watt. ( the very biggest get down to 8 degr./W), and a heatsink is needed when power exceeds a few watts. Peter Alfke, Xilinx Applications

For all the VLSI devices I have used in the last few years, the maximum temperature ratings were die temperature, not ambient for the reasons you specify. As VLSI power dissipation is very dependent on operating mode, ambient ratings are pretty meaningless not only for programmable parts, but for the majority of VLSI. Things become quite difficult when the mfr has neglected to put a thermal sensing diode (really a transistor) on the die somewhere.

I suggest the OP grab the rather useful power dissipation calculator from the Xilinx website and then apply it using the Theta J-A for the device he is using.

Cheers

PeteS