Design Article
FPGA-based instrumentation withstands chill in deep space
Alireza Bakhshi, B&A Engineering Systems Inc.
9/12/2012 8:49 AM EDT
TEST RESULTS
Cryogenic testing was done using liquid nitrogen. We started the testing at room temperature of 24°C, having programmed the test chamber to proceed in steps to 10°C, 0°C, -10°C, all the way down to -150°C. Figure 2 charts Xilinx voltage currents vs. the temperature.
In the course of our testing, we made some interesting observations. For starters, we found that the 2.5V/2.5V auxiliary voltage currents remained stable over the test temperature range. Both of these voltages are used for system monitor and JTAG communication. All of the I/Os are tied to 3.3V.
Second, the internal 1.0V current was significantly reduced from 140 mA at +20°C to 81 mA at -150°C. This was no surprise, since a reduction in power is expected at low temperatures.
Finally, we found that the flash memory’s 1.8V current remained almost zero down to -50°C and then changed to 10 mA from -50 to -90°C. It dropped to zero from the -100 to -120°C temperature range, and went back to 10 mA from -130 to -150°C. We are not sure what to make of this finding; it could be due to test measurement errors.
Importantly, both clocks remained stable over the test temperature range (see Figure 3). We used a PLL to both divide and multiply the master on-board 100-MHz oscillator so as to generate the 50- and 150-MHz clocks.
Next: XILINX LOGIC
Cryogenic testing was done using liquid nitrogen. We started the testing at room temperature of 24°C, having programmed the test chamber to proceed in steps to 10°C, 0°C, -10°C, all the way down to -150°C. Figure 2 charts Xilinx voltage currents vs. the temperature.
Figure 2 – Xilinx FPGA voltage currents vs. temperature
In the course of our testing, we made some interesting observations. For starters, we found that the 2.5V/2.5V auxiliary voltage currents remained stable over the test temperature range. Both of these voltages are used for system monitor and JTAG communication. All of the I/Os are tied to 3.3V.
Second, the internal 1.0V current was significantly reduced from 140 mA at +20°C to 81 mA at -150°C. This was no surprise, since a reduction in power is expected at low temperatures.
Finally, we found that the flash memory’s 1.8V current remained almost zero down to -50°C and then changed to 10 mA from -50 to -90°C. It dropped to zero from the -100 to -120°C temperature range, and went back to 10 mA from -130 to -150°C. We are not sure what to make of this finding; it could be due to test measurement errors.
Importantly, both clocks remained stable over the test temperature range (see Figure 3). We used a PLL to both divide and multiply the master on-board 100-MHz oscillator so as to generate the 50- and 150-MHz clocks.
Figure 3 – Xilinx 50/150-MHz clock vs. temperature
Next: XILINX LOGIC
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LJL1
9/13/2012 2:47 AM EDT
One might expect that the differential shrinking between metal and silicon would cause broken traces on the die. Can you say whether or not this may have happened?
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elektryk321
9/13/2012 3:55 AM EDT
High temperature makes problems with silicon devices by fast electrons movement and power dissipation. Low temperature makes no problem for silicon design itself, but for mechanical design like wiring inside package, crystal oscillators or electrical interconnects. I do not feel this mechanical problems are big deals for any other IC manufacturers.
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