Cold Temperature Issue

Hi Farabi,

Thanks for your reply,

No further question, 

It seemed the configuration failure at cold  temperature cause by voltage translator of the nSTATUS signal,

The following is summarized of the FPGA cold start issue finding:

The design:

nCONFIG and nSTATUS signals pass trough voltage translator 3.3V to 1.8V, this translator is an Auto-direction sensing, when it detects rising or falling in one side it pulls the other side to proper state. 

Finding:

We observed that during 1.8V ramp up many signals connected to the FPGA pulled high or low for few micro- seconds – see below.

(1.8V = Vccio_SDM – FPGA SDM voltage)

After our understanding that the issue is not because the nCONGIF signal, we examine the nSTATUS signal.

In normal operation nSTATUS should rise during power-up and then follow the nCONFIG signal.

It should not pull low during power-up by external host.

In cases the configuration failed we found that the nSTATUS is stack low, the reason is that the translator detect the nSTATUS falling during start-up and pull it low, if we change the pull-up resistor on the nSTATUS signal from 10K to 1K the translator is not able to pull it low and configuration succussed.

Failed configuration

Configuration succussed with 1K pull-up on nSTATUS