Volterra Semiconductor LLC

Patent Trials and Appeals Board

Mar 4, 2021

IPR2020-01348 (P.T.A.B. Mar. 4, 2021)

Trials@uspto.gov Paper 19
571-272-7822 Date: March 4, 2021

UNITED STATES PATENT AND TRADEMARK OFFICE

BEFORE THE PATENT TRIAL AND APPEAL BOARD

MONOLITHIC POWER SYSTEMS, INC.,
Petitioner,
v.
VOLTERRA SEMICONDUCTOR LLC,
Patent Owner.

IPR2020-01348
Patent 7,525,408 B1

Before KEVIN F. TURNER, BARBARA A. PARVIS, and
MONICA S. ULLAGADDI, Administrative Patent Judges.

TURNER, Administrative Patent Judge.
DECISION
Denying Institution of Inter Partes Review
35 U.S.C. § 314
I. INTRODUCTION
Monolithic Power Systems, Inc. (“Petitioner”) filed a Petition (Paper
1 (“Pet.”)) requesting an inter partes review of claims 1–20 of U.S. Patent
No. 7,525,408 B1 (Ex. 1001, “the ’408 Patent”) pursuant to 35 U.S.C.
§§ 311–319. Volterra Semiconductor LLC (“Patent Owner”) filed a
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Patent 7,525,408 B1
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Preliminary Response. Paper 8 (“Prelim. Resp.”). Additional briefings were
made by the parties, as discussed below.
We have authority to determine whether to institute an inter partes
review. See 35 U.S.C. § 314 (2016); 37 C.F.R. § 42.4(a) (2019). The
standard for instituting an inter partes review is set forth in 35 U.S.C.
§314(a), which provides that an inter partes review may not be instituted
“unless . . . there is a reasonable likelihood that the petitioner would prevail
with respect to at least 1 of the claims challenged in the petition.” For the
reasons explained below, we discretionarily deny institution of an inter
partes review of the ’408 Patent.
II. BACKGROUND
A. Real Parties-in-Interest
Petitioner identifies itself as the real party-in-interest. Pet. 117.
Patent Owner names itself and Maxim Integrated Products, Inc. as the real
parties-in-interest. Paper 3, 2.
B. Related Matters
As required by 37 C.F.R. § 42.8(b)(2), each party identifies a judicial
matter that would affect, or be affected by, a decision in this proceeding. In
particular, the parties inform us that the ’408 Patent is asserted in the in the
following district court case: Volterra Semiconductor LLC v. Monolithic
Power Systems, Inc., No. 1:19-cv-02240-CFC (D. Del.) (“parallel district
court proceeding”). Pet. 117–118; Paper 3, 2.
Petitioner has also contemporaneously filed IPR petitions directed to
U.S. Patent Nos. 6,362,986 B1 (IPR2020-01368 and IPR2020-01370) and
7,772,955 B1 (IPR2020-01350 and IPR2020-01351). Paper 3, 2.
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Patent 7,525,408 B1
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C. The ’408 Patent
The ’408 Patent relates to construction of a coupled inductor within a
multi-phase DC-to-DC1 converter. Ex. 1001, 1:16–18. The magnetic core
constructions enable a scalable N-phase coupled inductor, where N is an
integer greater than 1, so that it has certain “desirable characteristics, such as
ripple current reduction and ease of implementation.” Id. at Abs., 2:52–53.
Figure 1 illustrates an N-phase coupled inductor for use in a multi-phase
DC-to-DC converter system (10) and is reproduced below.

Figure 1 illustrates a schematic view of the system of the ’408 Patent.
The ’408 Patent details that system 10 includes a power source 12
electrically coupled with N switches 14 and N inductors 24, for supplying
power to a load 16. Id. at 3:47–49. Each switch and inductor pair 14, 24

1 DC is direct current.
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Patent 7,525,408 B1
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represent one phase 26 of system 10 and inductors 24 cooperate together as a
coupled inductor 28. Id. at 3:49–51. In operation, DC-to-DC converter
system 10 converts an input signal 18 from a power source 12 (e.g., a
battery) to an output signal 30. Id. at 3:58–59.
In one embodiment, illustrated in Figures 12 and 13, reproduced
below, shows a magnetic core construction to implement a scalable multi-
phase coupled inductor 100 for inductor 28 in Figure 1.

Figure 12 illustrates an assembly view of a coupled inductor, with
annotations added by Petitioner. Pet. 4 (citing Ex. 1001, Fig. 12).
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Figure 13 illustrates a surface view of a coupled inductor.
Figures 12 and 13 show U-Shaped magnetic cores 102. Id. at 9:51–
52. The magnetic cores 102 may connect through printed circuit board
(“PCB”) 101 to bus bars 103 to form magnetic core cells. Id. at 9:52–54.
The two bus bars 103 may be affixed to one side of PCB 101 such that the
“magnetic cores 102 traverse through the PCB 101 from the opposite side of
the PCB (e.g., via apertures 101H) to physically couple to the bus bars 103.”
Id. at 9:54–58. Each magnetic core 102 may implement a single phase for
the inductor 100; thus, the inductor 100 may be scalable by adding a
magnetic core 102 and a winding (windings 104, 105) for each phase. Id. at
9:59–62, 9:64–66. For example, the three-phase inductor 100 shown in
Figures 12 and 13 has three magnetic cores 102 coupled to bus bars 103 with
each magnetic core 102 having a winding (windings 104, 105). Id. at 9:62–
67.
The bus bars and cores may be arranged in different ways. For
example, the center axes 402 of bus bar 103 may be orthogonal to (Figure
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Patent 7,525,408 B1
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12) or less than 90 degrees from (Figure 13) the center axes 404 of magnetic
cores 102. Alternatively, in an embodiment illustrated in Figure 14, “a
scalable coupled inductor 150” with bar magnetic cores 152, 153 are
respectively mounted to opposing sides 156, 157 of PCB 151. Id. at 10:21–
26, Fig. 14.
The ’408 Patent also including the following paragraph, which
includes an incorporation by reference:
One known DC-to-DC converter offers improved ripple reduction
that either reduces or eliminates the afore-mentioned difficulties.
Such a DC-to-DC converter is described in commonly owned U.S.
Pat. No. 6,362,986 issued to Schultz et al., incorporated herein by
reference. The '986 patent can improve converter efficiency and
reduce the cost of manufacturing DC-to-DC converters.
Ex. 1001, 2:4–10 (emphasis added).
D. Illustrative Claims
Petitioner challenges claims 1–20 of the ’408 Patent. Pet. 6. Claims
1, 8, and 14 are the independent claims, with the remaining claims ultimately
dependent on those claims. Independent claims 1 and 14, reproduced below,
are illustrative of the claimed subject matter.
1. An N-phase coupled inductor for magnetically coupling N
phases of a power converter, comprising:
a magnetic core including a first and second magnetic element and N
connecting magnetic elements, N being an integer greater than
one, the first and second magnetic elements being disposed
parallel to each other and separated by a linear separation distance,
each connecting magnetic element being coupled to the first and
second magnetic elements; and
N windings, each of the N windings for electrically connecting to a
respective phase of the power converter,
each connecting magnetic element having a respective one of the N
windings wound at least partially thereabout,
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Patent 7,525,408 B1
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two of the N windings being at least partially wound about a
respective one of the N connecting magnetic elements and one of
the first and second magnetic elements, and
N–2 of the N windings being at least partially wound about a
respective one of the N connecting magnetic elements and both of
the first and second magnetic elements.
14. An N-phase coupled inductor for magnetically coupling N phases
of a power converter, comprising:
a magnetic core including a first and a second magnetic element and
N connecting magnetic elements, N being an integer greater than
one, the first and second magnetic elements being disposed
parallel to each other and separated by a linear separation distance,
each connecting magnetic element being coupled to the first and
second magnetic elements, the first and second magnetic elements
and the N connecting elements cooperatively forming N-1
passageways; and
N windings, each of the N windings for electrically connecting to a
respective phase of the power converter,
each winding being wound about a respective connecting element and
at least partially through at least one passageway, and
each passageway having two of the N windings wound at least
partially therethrough.
Ex. 1001, 12:28–46, 14:4–21.
E. Asserted Grounds
Petitioner challenges the patentability of claims 1–20 of the
’408 Patent on the following grounds:
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Patent 7,525,408 B1
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Claims Challenged 35 U.S.C. § References
1–6, 14–19 103(a)2 Schultz3
7, 20 103(a) Schultz, Wong4
1, 2, 4, 5, 7–11, 14, 15, 17,
18, 20 103(a)
Wong, Xu5
12 103(a) Wong, Xu, Schultz
13 103(a) Wong, Xu, Philips Handbook6
Petitioner supports its challenge with a Declaration by Dr. Douglas Charles
Hopkins (Ex. 1002, “Hopkins Decl.”), and Patent Owner supports its
arguments with a Declaration by Dr. Tamas Szepesi (Ex. 2001, “Szepesi
Decl.”). The parties also provided supplemental briefing on the issue of the
Declaration of Teresa Shaw (Ex. 1024) and its effect on demonstrating the
public availability of Wong (Ex. 1007). See Papers 17, 18.
III. DISCRETIONARY DENIAL OF THE PETITION
Patent Owner contends we should exercise our discretion under
35 U.S.C. § 314(a) to deny institution of inter partes review because the
parallel district court proceeding involves the same parties, overlapping

2 The Leahy-Smith America Invents Act, Pub. L. No. 112–29, 125 Stat. 284
(2011) (“AIA”), amended 35 U.S.C. § 103. Because the ’408 Patent has an
effective filing date before the effective date of the applicable AIA
amendments, we refer to the pre-AIA version of 35 U.S.C. § 103.
3 U.S. Patent No. 6,362,986, filed March 22, 2001, issued March 26, 2002
(Ex. 1011, “Schultz”).
4 Pit-Leong Wong, Performance Improvements of Multi-Channel
Interleaving Voltage Regulator Modules with Integrated Coupling Inductors
(Mar. 28, 2001) (published Ph.D. dissertation, Virginia Polytechnic Institute
and State University) (available and searchable on WorldCat by May 22,
2001; available via Virginia Tech library’s electronic database on Apr. 25,
2002) (Ex. 1007, “Wong”).
5 U.S. Patent Application Publication No. US 2002/0118000 A1, published
August 29, 2002 (Ex. 1009, “Xu”).
6 Philips Electronics N.V., Soft Ferrites, 1998 Data Handbook (1997) (Ex.
1017, “Philips Handbook”).
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claims, and the same prior art, and because the parallel district court
proceeding will outpace the instant proceeding. Prelim. Resp. 1–9 (citing,
e.g., Apple Inc. v. Fintiv, Inc., IPR2020-00019, Paper 11 (PTAB Mar. 20,
2020) (precedential, designated May 5, 2020) (“Fintiv”)). We authorized the
parties to file supplemental briefing to address the Fintiv factors. Paper 9.
The parties filed their supplemental briefings. See Paper 10 (Pet. Reply);
Paper 11 (PO Sur-reply).
Patent Owner also contends we should exercise our discretion under
35 U.S.C. § 325(d) to deny institution of inter partes review because Schultz
was previously presented during prosecution of the ’408 Patent, and because
the combination of Wong and Xu represents substantially the same prior art
previously presented during prosecution. Prelim. Resp. 10–20. Petitioner,
in its Reply, argues that § 325(d) provides no basis for a discretionary denial
(Pet. Reply 7), and Patent Owner counters that § 325(d) favors denial of
institution (PO Sur-reply 7).
The Board has discretion not to institute an inter partes review. See
35 U.S.C. § 314(a) (authorizing institution of an inter partes review under
particular circumstances, but not requiring institution under any
circumstances); 37 C.F.R. § 42.108(a) (stating “the Board may authorize the
review to proceed”) (emphasis added); Harmonic Inc. v. Avid Tech, Inc., 815
F.3d 1356, 1367 (Fed. Cir. 2016) (explaining that under § 314(a), “the PTO
is permitted, but never compelled, to institute an IPR proceeding”). Patent
Owner contends that we should exercise that discretion and not institute trial
because of the state of the parallel district court litigation. Prelim. Resp. 1–
9. Because we determine that the information in the Petition fails to show a
reasonable likelihood that the petitioner would prevail with respect to at least
one of the Challenged Claims on another discretionary basis, we need not
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address Patent Owner’s contentions concerning discretionary denial under
§ 314(a). As such, we consider the parties’ contentions regarding whether
we should exercise our discretion under 35 U.S.C. § 325(d) to deny
institution of inter partes review.
A. 35 U.S.C. § 325(d)
Pursuant to 35 U.S.C. § 325(d), in determining whether to institute an
inter partes review, “the Director may take into account whether, and reject
the petition or request because, the same or substantially the same prior art
or arguments previously were presented to the Office.” In evaluating
arguments under § 325(d), we use
[a] two-part framework: (1) whether the same or substantially
the same art previously was presented to the Office or whether
the same or substantially the same arguments previously were
presented to the Office; and (2) if either condition of first part of
the framework is satisfied, whether the petitioner has
demonstrated that the Office erred in a manner material to the
patentability of challenged claims.
Advanced Bionics, LLC v. MED-EL Elektromedizinische Geräte GmbH,
IPR2019-01469 (PTAB Feb. 13, 2020) (Paper 6) (precedential), slip op. at 8.
See also Becton, Dickinson & Co. v. B. Braun Melsungen AG, IPR2017-
01586, Paper 8 at 17–18 (PTAB Dec. 15, 2017) (precedential as to Section
III.C.5, first paragraph) (listing factors to consider in evaluating the
applicability of § 325(d)).
Patent Owner contends we should exercise our discretion under
35 U.S.C. § 325(d) to deny institution of inter partes review because Schultz
was previously presented during prosecution of the ’408 Patent, and because
the combination of Wong and Xu represents substantially the same prior art
previously presented during prosecution. Prelim. Resp. 10–20. Petitioner,
in its Reply, argues that § 325(d) provides no basis for a discretionary denial
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(Pet. Reply 7), and Patent Owner counters that § 325(d) favors denial of
institution (PO Sur-reply 7). We consider the parties’ arguments below and
we determine there to be sufficient cause for us to deny institution under
§ 325(d).
1. Grounds of Unpatentability Applying Schultz
Patent Owner argues that Schultz was previously presented during
prosecution of the ’408 Patent, and the ’408 incorporates Schultz by
reference and is mentioned at least eight times in the ’408 patent
specification. Prelim. Resp. 11–13. Patent Owner also indicates that “[t]he
application that resulted in the ’408 Patent was never rejected during
prosecution and therefore Schultz never served as ‘the basis for rejection’
and nor were there any arguments made during examination during
prosecution.” Id. at 13. Additionally, Patent Owner argues that Petitioner
has not shown how or why the Examiner erred in allowing the claims after
considering Schultz. Id. at 14.
Petitioner responds that Figures 1, 10, and 14 of Schultz, upon which
the Petition relies, are not mentioned or discussed in the ’408 Patent, and the
“mere fact that Schultz was cited in an IDS, but not applied in any rejections,
is insufficient to trigger the 325(d) bar.” Pet. Reply 7 (citing Digital Check
Corp. v. E-ImageData Corp., IPR2017-00178, Paper 6 at 12-13 (Apr. 25,
2017)). Patent Owner disputes Petitioner’s characterization, arguing that
“Schultz was discussed extensively throughout the ’408 patent itself,” such
that it was “thoroughly presented to the Examiner before allowing the claims
over Schultz.” PO Sur-reply 7.
We agree with Patent Owner. The incorporation by reference of
Schultz into the ’408 Patent (see Section II.C) is clear and unambiguous. As
Patent Owner notes, Schultz is discussed at multiple points in the ’408
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Patent specification (PO Sur-reply 7), and it is difficult to suggest that the
Examiner merely “overlooked it.” The fact that specific figures of Schultz
are not explicitly depicted in the ’408 Patent is not availing of Petitioner’s
position (Pet. Reply 7) when Figure 1 of Schultz, noted for its omission by
Petitioner, appears on the cover of Schultz; even the most cursory review of
Schultz would provide notice of the figure on its cover. Additionally, the
nature of incorporation by reference connotes that all of Schultz would have
been considered to be part of the ’408 Patent specification and would have
been considered by the Examiner. See 37 C.F.R. § 1.57(e). Also, as Patent
Owner argues, Petitioner has provided no evidence or rationale that the
Examiner erred in allowing claims over Schultz. Prelim. Resp. 14. In fact,
the Petition is bereft of any acknowledgement that Schultz played any part in
the prosecution of the patent application that resulted in the issuance of the
’408 Patent. See generally Pet. No assertions were made by Petitioner in
the additional briefing either. See Pet. Reply 7. As such, we determine that
the same art that was previously presented to the Office is being presented
against the challenged claims, and Petitioner has not demonstrated that the
Office erred in a manner material to the patentability of the challenged
claims. Advanced Bionics, Paper 6 at 8. Thus, the inclusion of grounds
based on Schultz, without more from Petitioner, weighs heavily for
application of our discretion to deny institution of an inter partes review.
We make that determination even in view of Patent Owner’s apparent
acquiescence to the applicability of Schultz to independent claim 14: “[f]or
example, should the Board find no reasonable likelihood of success for
independent claims 1 and 8, yet determine that there is a reasonable
likelihood of success for claim 14, it would be proper to deny institution
under the discretion granted by § 314(a).” Prelim. Resp. 67–68. Patent
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Patent 7,525,408 B1
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Owner goes on to argue that it would not be an efficient use of our time and
resources “with respect to only a handful of the challenged claims.” Id. In
view of the present circumstances, we agree and determine that § 325(d) is
sufficiently implicated such that its statutory purpose would be undermined
by instituting on the remaining claims. See SAS Inst., Inc. v. Iancu, 138 S.
Ct. 1348 (2018).
With respect to the additional ground over Schultz and Wong, we
agree with Patent Owner that the addition of Wong is insufficient to discount
the application of our discretion under § 325(d). Prelim. Resp. 14–15 (citing
Kayak Software Corp. v. Int’l Bus. Mach. Corp., CBM2016-00075, Paper 16
at 10 (PTAB Dec. 15, 2016) (Informative)). The aspects added through
consideration of Wong do not change the overall consideration of Schultz in
the prosecution of the ’408 Patent.
2. Grounds of Unpatentability Applying Wong and Xu
Patent Owner also argues that because the combination of Wong and
Xu represents substantially the same prior art previously presented during
prosecution, we should deny institution. Prelim. Resp. 15–20. Patent
Owner argues that Petitioner relies upon Wong and Xu in the same manner
as the prior art presented to the Office previously. Id. at 16. Patent Owner
points to the similar three-dimensional renderings of schematic figures, and
argues that those representations demonstrate the “highly similar” natures of
the embodiments of the references considered by Petitioner. Id. at 16–17
(citing Pet. 22, 72). Patent Owner also relies on the testimony of its
declarant, Dr. Szepesi, that there are many similarities between the
embodiments discussed and that “there are no notable distinctions” between
how Petitioner and Dr. Hopkins apply the embodiment of Figure 10 of
Schultz and the proposed Wong-Xu combination to the challenged claims.
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Patent 7,525,408 B1
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Id. at 18 (citing Ex. 2001 ¶¶ 139–140); Ex. 2001 ¶ 140. Because of these
factors, Patent Owner argues that Petitioner “relies on the proposed Wong-
Xu combination in the same manner as the Schultz reference, which was
previous presented to the Office,” and that the Wong-Xu combination is
substantially the same art previously presented. Id. Patent Owner also
argues that additional secondary references added, such as Schultz and
Philips Handbook, are insufficient to refute the exercise of discretion under
35 U.S.C. § 325(d). Id. at 19 (citing Kayak Software, CBM2016-00075,
Paper 16 at 10).
We agree with Patent Owner. Petitioner has supplied no evidence or
argument to counter Patent Owner’s arguments regarding the similarity of
the combination of Wong and Xu in view of Schultz, although both parties
were allowed extra briefings regarding this issue. See generally Pet.; Pet.
Reply. See also Paper 9, 3 (authorizing counter arguments to “Patent
Owner’s § 325 (d) arguments” in the instant proceeding). Petitioner’s
arguments were limited solely to Schultz alone. Pet. Reply 7. We find
persuasive Dr. Szepesi’s testimony regarding the similarities in presentation
of the ground asserting Schultz with the ground asserting Wong-Xu. As
such, we determine that the combination of Wong and Xu constitutes
substantially the same art that was previously presented to the Office.
Similar to the Schultz grounds, Petitioner offers no evidence or argument
that the combination of Wong and Xu would have been viewed any
differently than Schultz.
Also, similar to the above discussion, even with Patent Owner’s
apparent acquiescence to the applicability of Wong and Xu to independent
claim 14 (Prelim. Resp. 68), we find that § 325(d) is sufficiently implicated
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15
that that its statutory purpose would be undermined by instituting on the
remaining claims.
3. Conclusion
Based on the above analysis, we agree with Patent Owner’s
contentions that we should also exercise our discretion under 35 U.S.C.
§ 325(d) to deny institution of an inter partes review.
IV. ORDER
In consideration of the foregoing, it is hereby:
ORDERED that Petitioner’s request for an inter partes review of
claims 1–20 of the ’408 Patent is denied.
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Patent 7,525,408 B1
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FOR PETITIONER:
Lionel M. Lavenue
Cory C. Bell
FINNEGAN, HENDERSON, FARABOW, GARRETT, & DUNNER LLP
lionel.lavenue@finnegan.com
cory.bell@finnegan.com

Bob Steinberg
Matthew J. Moore
Surendra K. Ravula
LATHAM & WATKINS LLP
bob.steinberg@lw.com
matthew.moore@lw.com
surendrakumar.ravula@lw.com

FOR PATENT OWNER:
Michael T. Hawkins
Nicholas Stephens
Kim Leung
David M. Barkan
Aaron P. Pirouznia
FISH & RICHARDSON P.C.
hawkins@fr.com
leung@fr.com
nstephens@fr.com
IPR24130-0039IP1@fr.com
PTABInbound@fr.com