b159- mapld - 2004burke1 operation of fpgas at extremely low temperatures gary burke, scott cozy,...

B159- MAPLD - 2004 Burke 1

Operation of FPGAs at Extremely Low Temperatures

Gary Burke, Scott Cozy, Veronica Lacayo, Alireza Bakhshi, Ryan Stern, Mohammad Mojarradi, Travis Johnson, Elizabeth Kolawa, Gary Bolotin, Tim Gregoire, and

Rajeshuni Ramesham

Jet Propulsion Laboratory, California Institute of Technology


Purpose of Cold temperature Testing

• The surface temperature of Mars can vary from -120C to +20C.

• In order to use qualified parts on a Mars Rover such as MER, it is necessary to enclose them in a protective box, known as a ‘warm-box’, where the temperature is controlled by resistive heating elements.

• This approach results in complex wiring, adding to mass and creating test problems


Why Cold-Temperature FPGAs

• The wiring could be simplified, if a bus system is used to send commands to control the peripherals.

• However, this then requires bus controllers to be outside of the warm-box, and subject to ambient temperatures.

• These controllers can be conveniently implemented with FPGAs


Types of test

• Can the FPGA operate normally at cold?

• Can the FPGA be powered up at cold?• Does the FPGA performance degrade over time?

• Will the FPGA package withstand the cold temperature and temperature cycling?– These are still being investigated


Devices tested - Actel

ACTEL FPGA

Density

(System

Gate)

RAM Radiation TID: krad(Si)

Package TMR

Temp (°C)

RT54SX72S *

108 K No 100 208-Pin Ceramic Quad FP

Yes -55 to +125

A54SX32A 48 K No No 144 Thin Quad FP No -40 to +85

* No results yet


Devices tested - Xilinx FPGA Xilinx

Density RAM Radiation TID: krad(Si)

Package Embedded

PowerPC

Temp (°C)

XQVR600

(tests in progress)

661 K

gates

Yes 100 228-Pin Ceramic Quad FP

No -55 to +125

XCVR600 661 K

gates

Yes No 240-Pin High Heat Dissipation Quad FP

No -40 to +100

XC2VP20-FF1152

9280 slices

Yes No 1152 -pin fine-pitched BGA

2 0 to +85


Test setup


FPGA Board Test Set Up -ACTEL


FPGA Board Test Set Up - Xilinx


Wire Wrap Board Test Set Up - Xilinx


Wire Wrap Board Test Set Up - ACTEL


Test Code – Actel and Virtex

•Test Code is Dual Counters •A ‘Fail’ bit is set if ms bits of

counter do not match•MSB bits and ‘fail’ are

displayed on LEDs to give instant fail information

•A set of registers is used to perform read/write tests


Test Code – Actel and Virtex

•Additional test outputs are programmed to allow testing of combinational delays

•Clock skew can be measured via test outputs

•(Note: Xilinx Pro – has different test code)


Actel Results

Commercial Actel FPGA (A54SX32A) results:

• Digital logic – functioned down to –165ºC

• Power cycling – functioned to –165ºC


Virtex Results

Commercial Xilinx FPGA (XCVR600) results:

• Digital logic– functioned down to –165ºC

• Power cycling– initialization current increased from 10 mA

at 0ºC to 800 mA (current limited) at –40ºC, and FPGA failed to initialize. Further tests were performed on this part.


Virtex Surge Current Test

• The Xilinx Virtex part exhibits startup surge current which increases at cold temperature

• The power supply limits (800 mA) prevents Xilinx part from configuring at cold temp.

• A further test was performed on the Xilinx Virtex part to measure surge current

• Setup was the same but larger power supplies and larger power cabling were used


Surge current at 20ºC


Surge current at -40˚C


Surge current vs. temperature

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

-160 -140 -120 -100 -80 -60 -40 -20 0 20 40

Temperature (ºC)

peak current (mA) pulse duration (μs)


Surge current summary

• The startup current is temperature dependant• The current peaks at –92ºC (5.22Amps)• At lower temperatures the startup current

decreases from the peak• The width of the current pulse has the same

temperature dependence• As long as sufficient current is supplied, the

Virtex part is able to be powered on and configured down to –140 ºC


Temperature Test for the Virtex-II PP Board

• The purpose for testing this board at low temperatures was to initially find out if the board and mainly the Virtex-II Pro FPGA part number XC2VP20-FF1152 would survive and continue operating at different temperature ranges.

• An additional test was to power off the board once it reached -120ºC and to see what happens when powered back.

• Based on Virtex testing, the FPGA was suspected to drain a lot of current of up to 10A.



• The Virtex-II PP Board was tested at different temperatures. The temperature range went from 25ºC to -120ºC.

• For this particular test, the board was powered using 3 power supplies. They were set up at the following voltages:– 3.3Vdc– 2.5Vdc and – 1.5Vdc.

• Surge current was measured on the 1.5V supply.



• The 3.3Vdc supplied power to the Electronics in the board.

• The 2.5Vdc supplied power to the I/O’s, banks, and Rocket I/O Transceivers.

• The 1.5Vdc supplied power to the FPGA core.• The test FPGA circuit runs self checking firmware

on 2 embedded processors, monitored via RS232 port



• The following values were measured before the test at room temperature (22.7ºC) in the lab. – V = 3.3V at 110mA.– V = 2.5V between 35mA and 41mA.– V = 1.5V at 221mA.



• The following are Voltage readings taken at different temperatures:– T0 = -5ºC, T1 = -2.4ºC and T2 = -1.8ºC:

• V = 3.3V at 110mA. • V = 2.5V between 35mA and 41mA.• V = 1.5V at 210mA.

– T0 = -55.8ºC, T1 = -50ºC and T2 = -50.4ºC:• V = 3.3V at 99mA. • V = 2.5V between 35mA and 41mA.• V = 1.5V at 210mA.

– T0 = -121.7ºC, T1 = -117.7ºC and T2 = -115.9ºC:• V = 3.3V at 96mA. • V = 2.5V between 35mA and 41mA.• V = 1.5V at 208mA.



• The board was never shut down as the temperature was decreased. The board never stopped working.

• Once it reached -120ºC, the temperature was brought back up. At intervals, we power cycle the board and measure the in rush current.

• It was found as temperature ramped up that the board always powered back on. At times, it was necessary to press the configuration switch, to reset the board



• T0 = -121.7ºC, T1 = -117.7ºC and T2 = -115.9ºC.

• At power on, the in rush current was of approximately 220mA for about 0.3ms then it drops to 170mV for about 22ms.



• T0 = -58.8ºC, T1 = -60.5ºC and T2 = -59.3ºC.

• There was no change in inrush current.



• T0= 21.9ºC, T1 = 16.9ºC and T2 = 16.8ºC.

• The in rush current never changed through-out the temperatures tested.



• The Virtex II Pro functioned correctly at temperatures down to –120ºC (limit of testing)

• The Virtex II Pro FPGA did not show a large rush current. The current peaked at 220mA.

• The excessive startup surge current seen on the Virtex chip at cold temperatures is not seen on the Virtex II Pro.


Summary

• All 3 of the FPGAs tested both Actel and Xilinx were functional down to –120ºC or lower.

• A large startup surge current was seen on the Xilinx Virtex part at cold temperatures.– If this current is not supplied, the part will not

configure

• The Xilinx Virtex II Pro does not have the surge current problem.

b159- mapld - 2004burke1 operation of fpgas at extremely low temperatures gary burke, scott cozy,...

Documents