Elbrus International Limited v. Samsung Electronics Co., Ltd.

N OTE: This disposition is nonprecedential.
United States Court of Appeals
for the Federal Circuit
______________________
ELBRUS INTERNATIONAL LIMITED,
Appellant
v.
SAMSUNG ELECTRONICS CO., LTD.,
Appellee
______________________
2017-1855
______________________
Appeal from the United States Patent and Trademark
Office, Patent Trial and Appeal Board in No. IPR2015-
01524.
______________________
Decided: June 27, 2018
______________________
P HILIP P. MANN, Mann Law Group, Seattle, WA, for
appellant.
N AVEEN M ODI, Paul Hastings LLP, Washington, DC,
for appellee. Also represented by S TEPHEN BLAKE
K INNAIRD, J OSEPH P ALYS ; J OSEPH J OHN RUMPLER, II, Palo
Alto, CA.
______________________
Before REYNA, BRYSON, and HUGHES , Circuit Judges.

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ELBRUS INT ’ L LTD. v. SAMSUNG ELECS. CO., LTD. 2
P ER CURIAM .
Elbrus International Ltd. appeals from the final writ-
ten decision in an inter partes review proceeding in which
the Patent Trial and Appeal Board found claims 1, 2, 5, 6,
and 9 of U.S. Patent No. 6,366,130 (“the ’130 patent”) to
be invalid. Samsung Elecs. Co., Ltd. v. Elbrus Int’l Ltd.,
No. IPR2015-01524, 2017 WL 379208 (P.T.A.B. Jan. 17,
2017). We affirm.
BACKGROUND
The ’130 patent, entitled “High Speed Low Power Da-
ta Transfer Scheme,” relates to a “high speed and lower
power” complementary metal-oxide semiconductor
(“CMOS”) data transfer arrangement. The arrangement
“includes two active pull up/pull down bus drivers, a
differential bus that precharges to a specific voltage level
and a latched differential sense amplifier that serves as a
bus receiver.” ’130 patent, col. 1, ll. 24–28.
Claim 1 is the only independent claim. It recites:
1. A data transfer arrangement comprising:
two bus drivers;
a voltage precharge source;
a differential bus coupled to the bus drivers
and to the voltage precharge source; a[n]d
a latching sense amplifier coupled to the dif-
ferential bus;
wherein the latching sense amplifier compris-
es:
a first stage including a cross-coupled latch
coupled to a differential data bus; and
an output stage coupled to an output of said
first stage;

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ELBRUS INT ’ L LTD. v. SAMSUNG ELECS. CO., LTD. 3
wherein the output of the first stage is coupled
to an input of the output stage; [and]
wherein the differential bus and the differen-
tial data bus are precharge[d] to a voltage Vpr be-
tween Vdd and ground, where Vpr=K*Vdd, and K
is a precharging voltage factor.
D ISCUSSION
I
Elbrus argues that the Board adopted an erroneous
construction of the claim term “bus.” Adopting Samsung’s
proposal, the Board construed “bus” as “one or more
conductors that are used for the transmission of signals,
data, or power.” Samsung Elecs. Co., 2017 WL 379208, at
*3. Elbrus contends that the Board should have adopted
its proposed construction, i.e., “a common path along
which power or signals travel from one or several sources
to one or several destinations.” Id. The meaning of the
term “bus” bears on whether Samsung’s lead prior art
reference, U.S. Patent No. 5,828,241 (“Sukegawa”), dis-
closes a “differential data bus,” as recited in claim 1.
Although the Board adopted Samsung’s construction,
it concluded that Sukegawa discloses a “differential data
bus” under both Samsung’s and Elbrus’s proposed con-
structions. Id. at *6–7. Because we find no error in the
Board’s conclusion, we need not address Elbus’s argu-
ments regarding the proper construction of “bus.”
Sukegawa is entitled “Signal Transmission Circuit
Providing Amplified Output from Positive Feedback of
Intermediate Amplifier Circuit.” It concerns “a type of
signal transmission circuit wherein the signal is amplified
and transmitted by means of the positive feedback of an
intermediate amplifier circuit having input/output shared
terminals.” Sukegawa, col. 1, ll. 11–15.

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ELBRUS INT ’ L LTD. v. SAMSUNG ELECS. CO., LTD. 4
As part of its petition, Samsung provided the follow-
ing annotated excerpt of figure 1 of Sukegawa:
In the diagram, Samsung identified the differential
data bus as the lines associated with nodes N3 and N4
(also labeled C), which connect the transistors 38–41 to
the transistors 34 and 35 as well as to CMOS inverters 36
and 37. See Sukegawa, col. 8, ll. 49–53.
The Board found that those lines disclosed a differen-
tial data bus under both Samsung’s and Elbrus’s proposed
constructions. The Board noted that Sukegawa “discloses
a ‘signal transmission circuit,’ wherein a signal is trans-
mitted to receiver circuit 4 containing output terminals
OUT and OUT_.” Samsung Elecs. Co., 2017 WL 379208,
at *6 (citing Sukegawa, col. 9, ll. 4–24). Those lines carry
electrical signals from the transistors to the inverters, a
function that satisfies Samsung’s construction of bus as
“one or more conductors that are used for the transmis-
sion of signals, data, or power.” Id. (citing Sukegawa, col.
8, ll. 59–64; col. 9, ll. 4–7; col. 9, ll. 14–24).

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ELBRUS INT ’ L LTD. v. SAMSUNG ELECS. CO., LTD. 5
The Board also found that the portion of figure 1 iden-
tified by Samsung satisfies Elbrus’s construction of “bus.”
Citing the figure and expert testimony, the Board found
that figure 1 shows “a finite, non-zero distance between
transistors 34 and 35 and inverters 36 and 37, respective-
ly, and discloses transmitting from one portion of the
circuit to another portion.” Id. at *7. From this, the
Board concluded that Sukegawa discloses a “bus” even
under Elbrus’s construction of “a common path along
which power or signals travel from one or several sources
to one or several destinations.” Id.
We find no error in the Board’s analysis. On appeal,
Elbrus argues that Sukegawa’s nodes have “no non-trivial
distance” and that there is no “transmission of signals,
data, or power” over those lines. Neither argument is
persuasive. As to the first, the Board cited testimony
from both Samsung’s and Elbrus’s experts that a wire of
some length would be needed to connect the transistors
and the inverters, even if a person of ordinary skill would
have been motivated to minimize the length of the wire.
Id. at *6–7. Elbrus’s argument that a “bus” must span a
“non-trivial distance” is new on appeal; in any event, it is
unpersuasive, as there is nothing in the patent to suggest
that the claim language is limited to a bus of a certain
minimum length. As to the second argument, Sukegawa’s
circuit 4, of which those identified lines are part, is a
receiver that plays a role in signal transmission, see
Sukegawa, col. 8, l. 49 to col. 9, l. 29, and that those lines
therefore carry “signals, data, or power.”
In sum, because Sukegawa discloses a “bus” under ei-
ther Samsung’s or Elbrus’s construction, we affirm the
Board’s conclusion and need not reach Elbrus’s other
claim construction arguments.
II
Elbrus next challenges the Board’s conclusion that
claim 1’s limitation of buses that are “precharge[d] to a

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ELBRUS INT ’ L LTD. v. SAMSUNG ELECS. CO., LTD. 6
voltage Vpr between Vdd and ground” would have been
obvious in light of Sukegawa and a 1984 article in the
IEEE Journal of Solid State Circuits by Nicky Chau-
Chun Lu & Hu H. Chao (“Lu”). The article, entitled
“Half-VDD Bit-Line Sensing Scheme in CMOS DRAM’s,”
describes a sensing scheme in which the bit line is pre-
charged to half VDD. The article teaches that “the half-VDD
bit-line sensing scheme has several unique advantages,
especially for high-performance high-density” CMOS
Dynamic Random Access Memory (“DRAM”), “compared
to the full-VDD bit-line sensing scheme used for” N-type
metal-oxide-semiconductor (“NMOS”) memory arrays or
“the grounded bit-line sensing scheme for” P-type metal-
oxide-semiconductor (“PMOS”) arrays in CMOS DRAM’s.
Elbrus raises two arguments on appeal. First, Elbrus
argues that Sukegawa teaches away from precharging the
bus to half of the supply voltage, as taught in Lu. Elbrus
argues that because Sukegawa used Vdd/2 precharging on
a portion of his circuit but not on the differential data bus,
this “strongly taught away from Vdd/2 precharging of the
‘differential data bus.’”
The Board found that Sukegawa does not teach away
from precharging the differential data bus to Vdd/2.
Samsung Elecs. Co., 2017 WL 379208, at *9. The Board
noted that Elbrus “does not direct us to anything in
Sukegawa that can be said to discourage a person of
ordinary skill in the art from pre-charging to Vdd/2,” and,
to the contrary, “the record is replete with evidence
demonstrating the advantages of precharging to a value
below Vdd, as set forth in Lu, and those advantages would
apply equally in the context of precharging the differen-
tial data bus.” Id.
Whether a reference teaches away from the claimed
invention is a question of fact, which is reviewed for
substantial evidence. Meiresonne v. Google, Inc., 849 F.3d
1379, 1382 (Fed. Cir. 2017). A reference “that ‘merely

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ELBRUS INT ’ L LTD. v. SAMSUNG ELECS. CO., LTD. 7
expresses a general preference for an alternative inven-
tion but does not criticize, discredit, or otherwise discour-
age investigation into’ the claimed invention does not
teach away.” Id. (quoting Galderma Labs., L.P. v. Tol-
mar, Inc., 737 F.3d 731, 738 (Fed. Cir. 2013)).
We conclude that substantial evidence supports the
Board’s factfinding that Sukegawa does not teach away
from applying the teachings of Lu. As the Board found,
nothing in Sukegawa discourages precharging a differen-
tial data bus to Vdd/2. At the oral hearing before the
Board, when asked “is there anything in the disclosure of
Sukegawa that we can look to to determine why he
charged to Vdd as opposed to some intermediate charge,”
Elbrus’s counsel responded, “I have not found anything
that says exactly why he did that.” Counsel then elabo-
rated, saying that Sukegawa “doesn’t say exactly why he’s
doing it. So we can only infer that he must have had a
reason . . . . But it’s not in Sukegawa. I admit that.”
Given that “a particular reference’s mere silence about a
particular feature does not tend to teach away from it,” In
re Haase, 542 F. App’x 962, 967 (Fed. Cir. 2013), the
Board’s conclusion that Sukegawa does not teach away
from precharging a differential data bus to Vdd/2 is
supported by substantial evidence.1
1 Elbrus’s reliance on In re Urbanski, 809 F.3d 1237
(Fed. Cir. 2016), and McGinley v. Franklin Sports, Inc.,
262 F.3d 1339 (Fed. Cir. 2001), is misplaced. As stated in
Urbanski, “[i]f references taken in combination would
produce a seemingly inoperative device, . . . such refer-
ences teach away from the combination and thus cannot
serve as predicates for a prima facie case of obviousness.”
809 F.3d at 1243 (quoting McGinley, 262 F.3d at 1354).
However, the Board rejected Elbrus’s argument that
combining Sukegawa and Lu would lead to an unworka-
ble circuit. Instead, the Board credited Samsung’s ex-

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ELBRUS INT ’ L LTD. v. SAMSUNG ELECS. CO., LTD. 8
Second, Elbrus argues that combining Lu with
Sukegawa would lead to an inoperable circuit absent
significant additional design work. However, “it is not
necessary that [Sukegawa and Lu] be physically combin-
able to render [a claim] obvious.” Allied Erecting &
Dismantling Co. v. Genesis Attachments, LLC, 825 F.3d
1373, 1381 (Fed. Cir. 2016) (quoting In re Sneed, 710 F.2d
1544, 1550 (Fed. Cir. 1983)). That is so because “‘[t]he
test for obviousness is not whether the features of a
secondary reference may be bodily incorporated into the
structure of the primary reference,’ but rather whether ‘a
skilled artisan would have been motivated to combine the
teachings of the prior art references to achieve the
claimed invention.’” Id. (quoting In re Keller, 642 F.2d
413, 425 (CCPA 1981), and Pfizer, Inc. v. Apotex, Inc., 480
F.3d 1348, 1361 (Fed. Cir. 2007)). Therefore, Elbrus’s
argument that combining Sukegawa and Lu could lead to
an unworkable circuit is “basically irrelevant.” In re
Etter, 756 F.2d 852, 859 (Fed. Cir. 1985) (en banc).
In any event, the Board’s conclusion that any opera-
bility hurdles in modifying Sukegawa’s circuit in view of
Lu’s teachings would be overcome by a person of ordinary
skill is supported by substantial evidence. The Board,
crediting Samsung’s expert and discounting the testimony
of Elbrus’s expert, found that operability issues would
arise only if “the modified Sukegawa system was designed
poorly,” and that a person of ordinary skill would have
been able to make “simple adjustments” to the circuit to
pert’s testimony that only “simple adjustments” were
necessary to ensure that “the circuit worked and didn’t
fail.” Samsung Elecs. Co., 2017 WL 379208, at *10. As
discussed below, substantial evidence supports the
Board’s conclusion. Inoperability therefore is not a basis
for finding that Sukegawa teaches away from applying Lu
to obtain the claimed invention.

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ELBRUS INT ’ L LTD. v. SAMSUNG ELECS. CO., LTD. 9
make it work.2 Samsung Elecs. Co., 2017 WL 379208, at
*10. Elbrus’s arguments on appeal do not provide a basis
to disturb the Board’s weighing of the expert evidence on
that point, and we therefore affirm.
III
Finally, Elbrus argues that the Board erred in finding
that claim 7 would have been obvious in light of the
combination of Sukegawa with Lu and U.S. Patent No.
6,249,469 B1 (“Hardee”). Claim 7 depends from claims 1
and 2. Claim 2 adds to claim 1 that “the bus drivers
comprise active pull-up and active pull-down bus drivers.”
Claim 7 then adds that “the active pull up and pull down
bus drivers are NMOS transistors.” According to the
petition, Sukegawa discloses active pull down drivers that
are NMOS transistors, but discloses PMOS transistors for
the pull up drivers. As a result, Samsung relies on Hard-
ee to show NMOS transistors as pull up and pull down
drivers.
The Hardee patent, entitled “Sense Amplifier with
Local Sense Drivers and Local Read Amplifiers,” is di-
rected to “a CMOS sense amplifier with local write driver
transistors to eliminate the pattern sensitivities and
delays of the prior art.” Hardee, col. 4, ll. 58–60. The
2 Elbrus complains that the Board misapprehended
the testimony of its expert, Dr. Huber, when the Board
stated: “We have considered Dr. Huber’s testimony that
modifying Sukegawa in view of Lu may lead to ‘power-
wasting current paths.’” Samsung Elecs. Co., 2017 WL
379208, at *10. Elbrus argues that Dr. Huber testified
that the modification would lead to power-wasting cur-
rent paths. In light of the fact that the Board credited
Samsung’s expert’s opinion that simple modifications
avoid this issue, any imprecision in the Board’s para-
phrase of Dr. Huber’s testimony is inconsequential.

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ELBRUS INT ’ L LTD. v. SAMSUNG ELECS. CO., LTD. 10
parties do not dispute that Hardee discloses NMOS pull
up and pull down transistors. See id. at col. 6, ll. 28–46;
id. at fig. 5.
The Board credited Samsung’s argument that a per-
son of ordinary skill would have been motivated to com-
bine the teachings of Hardee with those of Sukegawa.
Samsung Elecs. Co., 2017 WL 379208, at *14–16. The
Board agreed with Samsung that “substituting Hardee’s
NMOS pull up transistors for Sukegawa’s PMOS pull up
transistors would result in some area savings” on the
circuit. Id. at *15. The Board noted that the parties
disputed the magnitude of the space savings—Elbrus
argued that the savings would be only 0.8%; Samsung
argued that it would be 9%—but because it was “undis-
puted that modifying Sukegawa in view of Hardee would
result in some reduction in layout size,” the space-saving
feature would have been a motivation to combine the two
references. Id. In addition, the Board was persuaded by
Samsung’s argument that the combination would avoid
latch-up, which is a type of short circuit. Id. at *16.
Although Elbrus argued that “latch-up would not be a
problem in Sukegawa’s circuits” because the transistors
“do not receive or drive off-chip signals,” the Board credit-
ed Samsung’s evidence that latch-up is “not limited to
transistor circuits that drive external circuits.” Id.
Elbrus makes three arguments on appeal. First, El-
brus argues that the space savings offered by combining
Hardee with Sukegawa would be “trivial at best” and
would “not provide a meaningful incentive to make the
combination.” The Board’s conclusion that the space
savings—whether 0.8% or 9%—would motivate a person
of ordinary skill to combine the references is supported by
substantial evidence. In particular, the Board found
persuasive Samsung’s expert’s testimony that a reduction
in layout size can be an important consideration in circuit
design. Id. at *15.

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ELBRUS INT ’ L LTD. v. SAMSUNG ELECS. CO., LTD. 11
Second, Elbrus contends that Sukegawa does not ac-
tually exhibit latch-up, so the asserted motivation to
combine is illusory. Elbrus argues, as it did before the
Board, that Sukegawa does not have a latch-up problem
because all of the signals and transistors are on-chip.
However, the Board found credible the testimony of
Samsung’s expert testimony and Samsung’s other evi-
dence that latch-up can occur in transistor circuits that
drive internal circuits. That evidence included a 1998
article entitled “Understanding Latch-up in Advanced
CMOS Logic,” which explained that “[t]he cause of the
latch-up exists in all junction-isolated or bulk CMOS
processes.” The Board’s conclusion is therefore supported
by substantial evidence.
Finally, Elbrus argues that the Board relied on a mis-
apprehension of Dr. Huber’s testimony. The “misappre-
hension” appears to have originated in Elbrus’s own
patent owner’s response brief, in which Elbrus stated: “It
would not have been obvious to combine Hardee with
Sukegawa, since the alleged advantages are non-existent,
and such a substitution could require boosting voltages
above Vdd.” The Board quoted that sentence in its opin-
ion but concluded that it agreed with Samsung that “the
mere possibility of having to boost voltages above Vdd
does not detract from the aforementioned advantages
associated with modifying Sukegawa in view of Hardee’s
teachings.” Samsung Elecs. Co., 2017 WL 379208, at *16.
Elbrus now complains that the Board misunderstood the
evidence because Elbrus’s expert had stated that the
signals “would have to be boosted above VDD to pull the
driver outputs all the way to VDD.” However, Elbrus’s
expert explained that the voltage boost would have to
occur only if needed to achieve the “desirable (for both
speed and noise immunity)” condition that the outputs
“swing all the way to VDD or all the way to ground when
activated.” The Board therefore did not err in referring to

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ELBRUS INT ’ L LTD. v. SAMSUNG ELECS. CO., LTD. 12
Elbrus’s response that boosting voltage above Vdd could
occur, but is not required to.
Because substantial evidence supports the Board’s
finding that a person of ordinary skill would have been
motivated to combine Sukegawa with Hardee, we affirm
the Board’s conclusion that claim 7 would have been
obvious.
AFFIRMED

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