Tech Briefs Magazine - August 2021 - 19

Electrical/Electronics
Rad-Hard CMOS Crystal Oscillator
The oscillator is designed for localized clock signal generation and data transmission in
telemetry systems and remote sensing.
Goddard Space Flight Center, Greenbelt, Maryland
T
here is a need for rad-hard crystal stabilized
clock sources with at least 300
krad of total ionizing dose (TID) immunity.
A common solution has been to
spot-shield a commercial off-the-shelf
part or enclose it in a vault. Rad-hard
clock sources are needed for main electronics
boards (MEBs) and readout electronics
that need to operate in hazardous
space environments. Remote
sensing and telemetry require that the
readout circuits be co-located with the
sensors, which can be separated by an
arbitrary distance from the data processing
electronics.
A locally generated clock signal allows
the readout to generate its own clock signals
and to transmit the resulting data to
a remote receiver. If a crystal stabilized
carrier signal was available, the readout
could derive a clock signal that is an
integral submultiple of that carrier and
use the data generated from the clock
signal to modulate the carrier. The radiation
hardened by design (RHBD)
CMOS crystal oscillator may be used
directly or scaled in frequency to clock
an application circuit.
The RHBD CMOS crystal oscillator is
a comparator-based Pierce oscillator
that uses a piezoelectric crystal for accurate
and stable frequency generation.
The oscillator scheme differs from classic
Pierce oscillators that rely on at least
one inverter to achieve the required
gain. In the RHBD CMOS crystal oscillator,
a high-speed comparator provides
the gain with the crystal and linearizing
feedback resistor connected between
the comparator output and the inverting
input. The non-inverting input of
the comparator can be driven from a DC
signal source, such as a resistor divider,
voltage reference, or digital to analog
converter (DAC), for a variable common
mode in the feedback signal or a variable
duty cycle clock signal. Having the
ability to adjust the duty cycle of the
oscillator signal allows the system to com -
pensate for radiation-induced changes
such as input offset.
The comparator is a monolithic CMOS
rail-rail design with a proportional to
absolute temperature (PTAT) bias cell
fabricated with enclosed layout transistor
(ELT) devices and dual guard rings.
The ELTs provide high immunity to
TID-induced leakage and the dual guard
rings provide immunity to single event
latch-up (SEL). Together, the ELTs, dual
guard rings, and duty cycle adjustment
ensure robust operation of the circuit
even in the presence of high TID and
heavy ions.
NASA is actively seeking licensees to commercialize
this technology. Please contact
NASA's Licensing Concierge at AgencyPatent-Licensing@mail.nasa.gov
or call us
at 202-358-7432 to initiate licensing discussions.
Follow this link for more information:
https://technology.nasa.gov/patent/GSCTOPS-297.
Electronic
Hardware System Replicates Many Network
Architectures
The circuitry uses race logic to solve complex problems with a minimum expenditure of energy.
National Institute of Standards and Technology, Gaithersburg, Maryland
etworks underlie such real-life problems
as determining the most efficient
route for a trucking company to
deliver lifesaving drugs and calculating
the smallest number of mutations re -
quired to transform one string of DNA
into another. Instead of relying on software
to tackle these computationally
intensive puzzles, researchers created a
design for an electronic hardware system
that directly replicates the architecture
of many types of networks.
The researchers demonstrated the
hardware system using a computational
technique known as race logic to solve a
variety of complex puzzles both rapidly
and with a minimum expenditure of en -
N
Tech Briefs, August 2021
Cov
ergy. Race logic requires less power and
solves network problems more rapidly
than general-purpose computers.
A key feature of race logic is that it
encodes information differently from a
standard computer. Digital information
is typically encoded and processed using
values of computer bits - a 1 if a logic
statement is true and a 0 if it's false.
When a bit flips its value, say from 0 to 1,
it means that a particular logic operation
has been performed to solve a
mathematical problem.
In contrast, race logic encodes and
processes information by representing it
as time signals - the time at which a
particular group of computer bits transiwww.techbriefs.com
ToC
tions,
or flips, from 0 to 1. Large numbers
of bit flips are the primary cause of
the large power consumption in standard
computers. In this respect, race
logic offers an advantage because signals
encoded in time involve only a few carefully
orchestrated bit flips to process
information, requiring much less power
than signals encoded as 0s or 1s.
Computation is then performed by
delaying some time signals relative to others,
determined by the physics of the system
under study. For example, consider a
group of truck drivers who start at point
A and must deliver medicine to point E as
fast as possible. Different possible routes
go through three intersections: B, C, and
19
https://technology.nasa.gov/patent/GSC-TOPS-297 http://www.techbriefs.com http://www.abpi.net/ntbpdfclicks/l.php?202108MDNAV

Tech Briefs Magazine - August 2021

Table of Contents for the Digital Edition of Tech Briefs Magazine - August 2021

Tech Briefs Magazine - August 2021 - Intro
Tech Briefs Magazine - August 2021 - Sponsor
Tech Briefs Magazine - August 2021 - Cov1
Tech Briefs Magazine - August 2021 - Cov2
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