June 2006

NASA Electronic Parts and Packaging Program

**Performance Evaluation of an SOI (Silicon-On-Insulator) Crystal Clock
Generator**

**Under Extreme Temperatures**

Richard Patterson, NASA Glenn Research Center

Ahmad Hammoud, QSS Group, Inc. / NASA GRC

**Scope**

SOI-based devices are known to exhibit fast switching speeds, low power
consumption, reduced leakage currents, good radiation tolerance, and
extreme temperature operability. NASA could utilize this technology in
the design of reliable circuits and systems geared for use in space
exploration missions where severe operational conditions exist. For
example, planetary surface exploration, rovers and landers, planetary
orbiters, and deep space probes constitute missions where harsh
environments, such as extreme temperatures, are to be encountered. In
general, SOI devices are typically designed for use in high temperature
and radiation applications, however, little is known about their
performance at cryogenic temperatures. The objective of this work was to
evaluate SOI devices over an extended temperature range and to determine
their suitability for use in space exploration missions under extreme
temperatures.

A Honeywell high temperature crystal clock generator (HTCCG) integrated
circuit chip, which is fabricated using SOI processes and is designed
specifically for high temperature, was evaluated for use at cryogenic
temperatures. This device is rated for operation at temperatures as high
as 250 °C to 300 °C, and is tailored for use in applications such as
down-hole instrumentation, aerospace and avionics, gas and geothermal
wells, electric power conversion, and turbine engine and nuclear reactor
controls \[1\]. It operates from input crystal frequencies of 48 kHz to
40 MHz, or can be driven by an external clock. The base frequency output
ranges from 24 kHz to 20 MHz, with divide by two, four, and eight
frequency outputs also provided. Table I shows some specifications of
this SOI high temperature crystal clock generator \[1\].

Table I. Manufacturer's specifications of the SOI crystal clock
generator \[1\].

  ------------------------------------------------ ----------------------
  **Parameter, (Unit)**                            **Rating**

  Operating temperature, T (°C)                    --55 to +225

  Supply voltage, V~DD~ (V)                        5

  Supply current, I~S~ (mA)                        \< 10

  Crystal frequency range                          24 kHz-20MHz

  Package                                          14-lead ceramic DIP

  Part \#                                          22021014-003

  Lot Number                                       21014-4D93
  ------------------------------------------------ ----------------------

The device was characterized in the temperature range of -195 °C to
+100 °C. Using an external square wave clock signal with frequency of
500 kHz and 1 MHz, the four frequency outputs of the clock generator
(F~OUT~, F~OUT/2~, F~OUT/4~, and F~OUT/8~) were recorded at various test
temperatures. The chip supply current and its output signal
characteristics in terms of rise time, fall time, and duty cycle were
also obtained as a function of temperature. Profiles of the frequency
outputs were obtained using a LeCroy Waverunner LT374 digital storage
oscilloscope. In addition, cold-restart capability of the crystal clock
generator was examined by switching the power on after soaking the
device at -195 °C for a period of 20 minutes.

**Results and Discussion**

*Temperature Effects*

The F~OUT~, F~OUT/2~, F~OUT/4~, and F~OUT/8~ frequency outputs of the
crystal clock generator obtained at room temperature are shown in
Figure 1. These waveforms, which were acquired using an external clock
with frequency of 500 kHz and 1 MHz, were also obtained at test
temperatures of -50, -100, -150, -195, and +100 °C. No major distortion
was observed in the generated frequency outputs as test temperature was
varied throughout the range between -195 °C and 100 °C. For illustrative
purposes, only those frequency output waveforms obtained at the extreme
temperatures, i.e. -195°C and +100 °C are presented here as shown in
Figures 2 and 3, respectively.

![](media/image1.png){width="2.997916666666667in"
height="1.9819444444444445in"}

500 kHz

![](media/image2.png){width="2.9965277777777777in"
height="1.9548611111111112in"}

1 MHz

Figure 1. Waveforms of frequency outputs (F~OUT~, F~OUT/2~, F~OUT/4~,
and F~OUT/8~) at +20 °C.

![](media/image3.png){width="2.9965277777777777in"
height="1.9472222222222222in"}

500 kHz

![](media/image4.png){width="2.9972222222222222in"
height="1.9402777777777778in"}

1 MHz

Figure 2. Waveforms of frequency outputs (F~OUT~, F~OUT/2~, F~OUT/4~,
and F~OUT/8~) at -195 °C.

![](media/image5.png){width="2.995833333333333in"
height="1.9548611111111112in"}

500 kHz

![](media/image6.png){width="2.9993055555555554in" height="1.9375in"}

1 MHz

Figure 3. Waveforms of frequency outputs (F~OUT~, F~OUT/2~, F~OUT/4~,
and F~OUT/8~) at +100 °C.

The effect of temperature on the duty cycle, rise time, and fall time of
the F~OUT~ frequency output was examined thoroughly over the temperature
range of +100 °C to -195 °C. Figure 4 shows the duty cycle of the F~OUT~
signal as a function of temperature for two different clock frequencies,
500 kHz and 1 MHz. It can be seen that the duty cycle remained largely
unaffected by temperature except at the extreme low temperature of -195
°C. At this cryogenic temperature, the duty cycle of the F~OUT~ signal
began to exhibit a decrease. This change in the duty cycle, however, was
very minimal as it decreased only from 49.97% at 20 °C to 49.73% at -195
°C for 500 kHz clock frequency, and from 49.88% at 20 °C to 48.19% at
-195°C when 1 MHz external clock was used.

![](media/image7.wmf)

Figure 4. Duty cycle of F~OUT~ signal versus temperature.

The rise time and fall time of the F~OUT~ signal are shown in Figure 5
as a function of temperature. These results were the same regardless of
the frequency of the external clock signal, i.e. 500 kHz or 1 MHz. It ca
be clearly seen that while the rise time underwent very slight decrease
(from11ns to 9 ns) with decrease in temperature from +100 °C to -50 °C,
it maintained a steady value of 9 ns as temperature was further
decreased from -50 °C to -195 °C. Unlike its rise time counterpart, the
fall time of the F~OUT~ signal exhibited a change only at the cryogenic
temperature level of -150 °C and lower. For example, while the fall time
displayed a value of 9 ns between +100 °C and -100 °C, it dropped to 8
ns at test temperatures between -150 °C and -195 °C.

![](media/image8.wmf)

Figure 5. Rise time and fall time of the F~OUT~ signal as a function of
temperature.

Figure 6 shows the supply current of the crystal clock generator as a
function of temperature. It is evident that the supply current exhibited
a gradual, slight decrease in its value with decrease in test
temperature. This dependency of the supply current of the device on
temperature was almost linear, and occurred at either frequency of the
applied external clock signal.

![](media/image9.wmf)

Figure 6. Supply current of the SOI clock generator versus temperature.

*Cold Re-Start*

Cold-restart capability of the SOI high temperature crystal clock
generator was investigated by allowing it to soak at -195 °C for at
least 20 minutes without the application of electrical bias. Power was
then applied to the device and measurements were taken on the output
characteristics. The SOI clock generator was able to successfully cold
re-start at -195 °C, and the results obtained were the same as those
obtained earlier at that temperature.

**Conclusion**

The performance of an SOI high temperature crystal clock generator
(HTCCG) was evaluated in the temperature range of -195 °C to +100 °C for
potential use at cryogenic temperatures. The four frequency outputs of
the clock generator (F~OUT~, F~OUT/2~, F~OUT/4~, and F~OUT/8~) were
recorded at selected test temperatures using an external square wave
clock signal with frequency of 500 kHz and 1 MHz. The chip output signal
characteristics in terms of rise time, fall time, and duty cycle were
also obtained as a function of temperature. In addition, cold re-start
capability of the device was investigated at -195 °C. The preliminary
results indicate that this SOI-based device, which is designed for high
temperature applications, could potentially be used at cryogenic
temperatures. No significant change in the performance of the device or
major deviation in its output characteristics were observed upon
exposure to extreme temperatures between -195 °C to +100 °C. It was also
found that this SOI HTCCG was able to cold re-start at -195 °C. Finally,
the ceramic-packaged device experienced no structural or physical damage
due to the extreme temperature exposure. It is recommended that
additional comprehensive testing be carried out to assess the
reliability of these devices for long term use under extreme
temperatures in space exploration missions.

**References**

\[1\]. Honeywell Company, High Temperature Crystal Clock Generator HTCCG
Data Sheet, Form #900203, January 2006.

**Acknowledgments**

This work was performed under the NASA Glenn Research Center GESS
Contract \# NAS3-00145. Funding was provided by the NASA Electronic
Parts and Packaging (NEPP) Program under the task "Reliability of SiGe,
SOI, and Advanced Mixed Signal Devices for Cryogenic Power Electronics".