Cirrus Logic, Inc.

Patent Trials and Appeals Board

Mar 11, 2020

14706587 - (D) (P.T.A.B. Mar. 11, 2020)

UNITED STATES PATENT AND TRADEMARK OFFICE
UNITED STATES DEPARTMENT OF COMMERCE
United States Patent and Trademark Office
Address: COMMISSIONER FOR PATENTS
P.O. Box 1450
Alexandria, Virginia 22313-1450
www.uspto.gov
APPLICATION NO. FILING DATE FIRST NAMED INVENTOR ATTORNEY DOCKET NO. CONFIRMATION NO.
14/706,587 05/07/2015 Eric J. King 141841.00141-2238US 3555
115799 7590 03/11/2020
Cirrus Logic c/o Jackson Walker LLP
c/o Jackson Walker, L.L.P.
100 Congress Avenue
Suite 1100
Austin, TX 78701
EXAMINER
DE LEON DOMENECH, RAFAEL O
ART UNIT PAPER NUMBER
2838
MAIL DATE DELIVERY MODE
03/11/2020 PAPER
Please find below and/or attached an Office communication concerning this application or proceeding.
The time period for reply, if any, is set in the attached communication.
PTOL-90A (Rev. 04/07)

UNITED STATES PATENT AND TRADEMARK OFFICE
____________

BEFORE THE PATENT TRIAL AND APPEAL BOARD
____________

Ex parte ERIC J. KING, JOHN L. MELANSON, and SIDDARTH MARU

Appeal 2019-002542
Application 14/706,587
Technology Center 2800
____________

Before JOHN A. EVANS, JOHN P. PINKERTON, and
MICHAEL M. BARRY, Administrative Patent Judges.

PINKERTON, Administrative Patent Judge.

DECISION ON APPEAL

Pursuant to 35 U.S.C. § 134(a), Appellant1 appeals from the
Examiner’s decision to reject claims 1–18, which are all of the claims
pending in this application. We have jurisdiction under 35 U.S.C. § 6(b).
We REVERSE.

1 We use the word “Appellant” to refer to “applicant” as defined in
37 C.F.R. § 1.42. Appellant identifies Cirrus Logic, Inc. as the real party in
interest. Appeal Br. 2.
Appeal 2019-002542
Application 14/706,587

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STATEMENT OF THE CASE2
Introduction
Appellant’s disclosed and claimed invention relates to “circuits for
audio devices, . . . and more specifically, to a switch mode amplifier for
driving an audio transducer of an audio device.” Spec. 1:15–18.
Illustrative Claim
Claims 1 and 10 are independent. Claim 1 is illustrative of the
subject matter on appeal and reproduced below:
1. A system, comprising:
an impedance estimator configured to estimate an
impedance of a passive load and generate a target current based
at least on an input voltage and the impedance;
a voltage feedback loop responsive to a difference
between the input voltage and an output voltage of the passive
load; and
a current controller configured to, responsive to the
voltage feedback loop, the impedance estimator, and the input
voltage, generate an output current to the passive load to generate
an output voltage that is a function of the input voltage.
Appeal Br. 12 (Claims App.).

2 Our Decision refers to the Final Office Action mailed February 22, 2018
(“Final”); Appellant’s Appeal Brief filed August 31, 2018 (“Appeal Br.”)
and Reply Brief filed February 20, 2018 (“Reply Br.”); the Examiner’s
Answer mailed December 20, 2018 (“Ans.”); and the Original Specification
filed May 7, 2015 (“Spec.”).

Appeal 2019-002542
Application 14/706,587

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References

Name Reference  Date
Hand et al. (Hand) US 7,259,618 B2   Aug. 21, 2007
Picha et al. (Picha) US 2002/0171475 A1 Nov. 21, 2002
Stanley US 2002/0167354 A1 Nov. 14, 2002
Groe US 6,060,950 May 9, 2000
Mihelich et al.
(Mihelich)
US 2011/0228945 A1 Sept. 22, 2011

Rejections on Appeal
The Examiner rejected claims 1, 8–10, 17, and 18 under 35 U.S.C.
§ 103 as being unpatentable over Hand and Picha. Final 2–8.
The Examiner rejected claims 2 and 11 under 35 U.S.C. § 103 as
being unpatentable over Hand, Picha, and Stanley. Id. at 8–9.
The Examiner rejected claims 3, 4, 12, and 13 under 35 U.S.C. § 103
as being unpatentable over Hand, Picha, and Groe. Id. at 9–11.
The Examiner rejected claims 5–7 and 14–16 under 35 U.S.C. § 103
as being unpatentable over Hand, Picha, and Mihelich. Id. at 12–16.

ANALYSIS
Based on Appellant’s arguments in the Briefs (Appeal Br. 4–10;
Reply Br. 2–4), the dispositive issue before us is whether the Examiner erred
in concluding the proposed combination of Hand and Picha renders claim 1
obvious.3 For the reasons discussed below, Appellant’s arguments persuade
us that the Examiner erred.

3 To the extent Appellant makes other arguments in the Briefs with respect
to the claims, we do not address them because our decision of this issue is
dispositive.
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The Examiner finds Hand discloses “[a] system comprising: an
impedance estimator configured to estimate an impedance of a passive
load,” as recited in claim 1. Final 3 (citing Hand 3:22–44, Fig. 1). The
Examiner finds Hand fails to disclose the remaining elements of claim 1, but
that Picha discloses those elements. Id. (citing Picha ¶¶ 127–29, Fig. 5).
The Examiner concludes that
[i]t would have been obvious to one of ordinary skill in the art
before the effective filing date of the claimed invention to have
modified the circuit of Hand to generate a target current based
at least on an input voltage and the impedance; a voltage
feedback loop responsive to a difference between the input
voltage and an output voltage of the load; and a current
controller configured to, responsive to the voltage feedback
loop, the impedance estimator, and the input voltage, generate
an output current to the load to generate an output voltage that
is a function of the input voltage, in order to improve the power
amplification efficiency of the amplifier circuit . . . , as taught
by Picha.

Id. at 3–4 (citing Picha ¶ 1).
Appellant argues that “no evidence or explanation is provided as to
how one of skill in the art would adapt Hand with such alleged teachings of
Picha to arrive at a functional combination that works, nor is evidence cited
or explanation given how such combination is supposed to work in order to
achieve a desired result.” Appeal Br. 5. According to Appellant, “the
Examiner’s statement of purported motivation is merely a statement of the
functionality of individual components of the various references, but does
not provide evidentiary basis, or explanation of why an ordinarily skilled
artisan would add such functionality.” Id. at 7. Appellant further argues that
in “modifying Hand as suggested by Picha, the impedance estimator of
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Hand is modified to such an extent that it completely changes the principle
of operation of Hand.” Id. at 8. Appellant explains that “the impedance
referenced in Hand is an already existing impedance whose amount of
impedance is measured,” whereas “the impedance referenced in Picha does
not exist ab initio, but is an impedance to be inserted into a circuit to achieve
a desired result.” Id. at 9–10 (citing Hand 3:22–44; Picha ¶¶ 127–129).
In response, the Examiner reiterates that one would modify Hand with
Picha “to improve the power amplification efficiency of the amplifier
circuit” and adds that
the type of impedance estimator circuit [in Picha] can be
implemented in power amplifiers like [the] . . . Class D
amplifiers . . . disclosed by Hand, which would led [sic] . . . a
person of ordinary skill in the art to modify . . . Hand with
Picha with the purpose of improving the power amplification
efficiency of the amplifier circuit as taught by Picha.

Ans. 5–7 (citing Picha ¶¶ 1, 24, 34, 180). With respect to Hand’s principle
of operation, the Examiner asserts that “both references teaches [sic] the
principle of comprising a control structure capable of estimating the
impedance of the load of an electronic circuit (in this case power amplifier
circuits), therefore the principle of operation of Hand would still be the
same.” Id. at 7. The Examiner further asserts that “the claim language of
Independent claims 1 and 10 only recites estimating the impedance of a load,
the claim language never specifies that the load impedance has to be an
existing impedance or a determined to-be-added impedance.” Id.
In the Reply Brief, Appellant contends that “[s]till painfully lacking
from the Examiner’s Answer is ‘a clear, evidence-supported account of the
contemplated workings of the combination [which] is a prerequisite to
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adequately explaining and supporting a conclusion that a relevant skilled
artisan would have been motivated to make the combination and reasonably
expect success in doing so.’” Reply Br. 2 (citing Personal Web
Technologies, LLC v. Apple, Inc., 848 F.3d 987, 994 (Fed. Cir. 2017)).
Appellant further contends that the Examiner’s proposed combination
“changes the principle of operation of Hand from a system in which an
existing impedance of an output load is measured, to a to-be-added
impedance.” Id. at 3. Appellant also disputes the Examiner’s interpretation
of claims 1 and 10 “for two reasons”: “[f]irst, the Appellant’s claim
language is wholly irrelevant to the Appellant’s argument that the
combination of the references changes the principle of operation of Hand,”
and “[s]econd, . . . the context and verb tense of independent Claims 1 and
10 clearly indicate that the impedance estimated in Claims 1 and 10 is an
existing impedance, not a to-be-determined impedance.” Id.
Appellant’s arguments are persuasive. “[O]bviousness concerns
whether a skilled artisan not only could have made but would have been
motivated to make the combinations or modifications of prior art to arrive at
the claimed invention.” Personal Web Technologies, 848 F.3d at 994. An
obviousness analysis should be “clearly explained, or cite[] evidence
showing, how the combination of the two references was supposed to work.”
Id. In addition, a prior art reference may not be modified in a way that
disrupts the reference’s contribution to the art. “Such a change in a
reference’s ‘principle of operation’ is unlikely to motivate a person of
ordinary skill to pursue a combination with that reference.” Plas-Pak Indus.,
Inc. v. Sulzer Mixpac AG, 600 F. App’x 755, 759 (Fed. Cir. 2015). “If
references taken in combination would produce a ‘seemingly inoperative
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device,’ . . . such references teach away from the combination and thus
cannot serve as predicates for a prima facie case of obviousness.” McGinley
v. Franklin Sports, Inc., 262 F.3d 1339, 1354 (Fed. Cir. 2001) (citation
omitted).4
Hand discloses a digital amplifier including a digital test signal
generator, a digital engine for converting the test signal to an analog signal,
and an output stage for receiving the analog signal and driving a load and a
sense resistor in series with the load. Hand 3:23–27. A comparator receives
a voltage across the sense resister and a reference voltage equal to the
resistance of the sense resistor times a threshold level of current. Id. at
3:27–31. “The comparator generates a binary signal indicating whether the
voltage across the sense resistor exceeds the reference voltage.” Id. at 3:31–
33. A processor calculates an impedance of the load based on the threshold
level of current and the value of the digital test signal corresponding to a
transition in the binary signal. Id. at 3:36–39. Based on the calculated
impedance, the processor automatically adjusts the processing of input
signals to optimize its performance for the detected load. Id. at 3:41–44.
Picha discloses a power amplifier including a controller that estimates
an active impedance that should be applied in series to a load element to
reduce the difference between the output signal and subsequent best output

4 See also In re ICON Health & Fitness, Inc., 496 F.3d 1374, 1382 (Fed. Cir.
2007) (explaining that “a reference teaches away from a combination when
using it in that combination would produce an inoperative result”); In re
Gordon, 733 F.2d 900, 902 (Fed. Cir. 1984) (finding no reason to modify a
prior-art device where the modification would render the device “inoperable
for its intended purpose”).

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signal VTRGT. Picha ¶ 127. The controller provides the estimated active
impedance to the active load. Id. The active load being set to the estimated
active impedance further refines the approximation of the subsequent best
output signal VTRGT. Id. ¶ 128. The active load tracks changes in VTRGT and
the approximation thereof and adjusts the active impedance accordingly to
obtain the best approximation of the subsequent best output signal VTRGT at
the output. Id. ¶ 129.
But, as Appellant contends, the Examiner’s proposed rationale to
combine the cited teachings of Hand and Picha does not adequately explain
how or why one of ordinary skill in the art would have adapted the passive
load impedance teachings of Hand with the active load impedance teachings
of Picha to arrive at the claimed invention (which, like Hand, focuses on
passive load impedance). In addition, modifying the cited teachings of Hand
with those of Picha in the manner proposed by the Examiner would change
Hand’s principle of operation because Picha’s disclosures of impedance
differ from Hand’s not only in type of impedance, but also in the way
impedance is used. Hand’s processor calculates an impedance existing on a
passive load (e.g., a speaker) due to a passive element (e.g., a sense resistor),
whereas Picha’s controller estimates the impedance to be added to an active
load due to an active load element. Picha describes setting the active load to
the estimated active impedance and adjusting the active impedance to
improve the target voltage, whereas, in Hand, it is the processing of the input
signals—not the impedance—that is adjusted based on the calculated
impedance. That Hand and Picha both generally disclose “a control
structure capable of estimating the impedance of the load of an electronic
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circuit (in this case power amplifier circuits)” does not bridge the gap
separating the two references. Ans. 7.
For the foregoing reasons, we decline to sustain the 35 U.S.C. § 103
rejection of claim 1. Independent claim 10 is a method claim that recites
substantially the same elements and is rejected for substantially the same
reasons as claim 1. See Appeal Br. 14 (Claims App.); Final 5–6. Therefore,
for the same reasons as those for claim 1, we decline to sustain the 35 U.S.C.
§ 103 rejection of independent claim 10. We likewise decline to sustain the
35 U.S.C. § 103 rejections of dependent claims 2–9 and 11–18, for which
the Examiner makes no findings to cure the deficiencies in the rejections of
independent claims 1 and 10.
CONCLUSION
We reverse the Examiner’s rejections of claims 1–18 under 35 U.S.C.
§ 103.
In summary:
Claims
Rejected
35 U.S.C. §  Basis Affirmed Reversed
1, 8, 9, 10, 17,
18
103 Hand, Picha 1, 8, 9,
10, 17,
18
2, 11 103  Hand, Picha,
Stanley
2, 11
3, 4, 12, 13 103 Hand, Picha,
Groe
3, 4, 12,
13
5–7, 14–16 103 Hand, Picha,
Mihelich
5–7, 14–
16
Overall
Outcome
1–18

REVERSED