Opinion ID: 4522728
Heading Depth: 3
Heading Rank: 1

Heading: The Plain Language of the Claims and the

Text: Written Description Do Not Support Importing a Directionality Restriction into the “Maintaining” Limitation The plain text of the claim does not place a directionality restriction on the “maintaining” limitation. Claims 8 and 10, the only two claims reciting the limitation, simply require that the phase difference between the input and the feedback clock signals is maintained within 180˚. ’507 patent, col. 4 ll. 51–53 (“maintaining the phase difference between the input signal and the feedback clock signal [within] approximately 180˚”). Neither claim states or implies that the phase difference between the two signals is calculated by how much the feedback signal “follows” or lags behind the input signal. ’507 patent, col. 4 ll. 33–39, 51–53. Accordingly, unless “the patentee has chosen to be his own lexicographer in the specification or has clearly disclaimed coverage during prosecution,” we must interpret claims according to their plain language. See E-Pass Techs., Inc. v. 3Com Corp., 343 F.3d 1364, 1370 Fed. Cir. 2003). But there is no such explicit definition or disclaimer. Outside of claims 8 and 10, the ’507 patent only refers to the “maintaining” limitation in two instances: in the Abstract and in the Summary of the Invention. ’507 patent, Abstract; ’507 patent, col. 2 ll. 3–11. In both cases, the limitation is described broadly, without a directionality modifier such as “behind.” Id. Case: 19-1343 Document: 43 Page: 14 Filed: 04/06/2020 14 PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD. ProMOS argues that one of the statements in the written description, “CKF is more than 180˚ behind CKI,” indicates that the “maintaining” limitation calculates the phase difference based on how much the feedback signal lags the input signal. Appellant Br. 12. The written description, however, supports no such inference. In discussing the sole embodiment, depicted in Figure 2, the ’507 patent recites: When the second phase detector 30 determines that CKF [the feedback clock signal] is more than 180˚ behind CKI [the input clock signal], the second phase detector 30 controls switch 28 to be at posi- tion (2). The inverted buffered clock signal is thus selected, so that the input clock signal CKI is re- versed by 180˚[.] Through the inversion, the phase difference needing to be compensated by the delay line 16’ is made less than 180˚ and within the nor- mal operation capabilities of the phase adjusting loop formed by phase detector 12, shift register 14’, and delay line 16’. ’507 patent, col. 3 ll. 7–15. This discussion of the preferred embodiment does not address the “maintaining” limitation. This passage explains that the phase detector “select[s]” the inverted buffered clock signal when it “determines” that the feedback signal is more than 180˚ behind the input signal. ’507 patent, col. 3 ll. 7–15. It does not state that this directionality requirement should also apply when the DLL is “maintaining” the phase difference between the two signals. ’507 patent, col. 3 ll. 7–15. ProMOS conflates the “determining” and “selecting” steps with the separate “maintaining” limitation. As disclosed in claims 8 and 10 of the patent, the “maintaining” limitation does not involve “determining” whether a phase difference exists or “selecting” an inverted buffered clock signal. Read plainly, the claim language states that the DLL maintains the phase difference between the two Case: 19-1343 Document: 43 Page: 15 Filed: 04/06/2020 PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD. 15 signals within approximately 180˚ by adjusting the input clock signal with a loop comprising a phase detector, shift register, and delay line when the determined phase difference is less than approximately 180˚. ’507 patent, col. 4 ll. 51–57. We need not construe the “maintaining” limitation so narrowly simply because an embodiment describes other steps, namely, the “determining” and “selecting” steps, which do have directional restrictions. In fact, this directionality restriction is captured by claim 13 of the ’507 patent, which includes the “determining” and “selecting” limitations: A method for reducing delay line length in a digital delay locked loop (DLL), the method comprising: determining whether a feedback clock signal in the DLL follows within a 180˚ phase difference behind an input clock signal; and selecting a switch position according to the determining step, including selecting a first switch position when the feedback clock signal follows behind the input clock signal with 180˚. ’507 patent, col. 4 l. 66–col. 5 l. 10 (emphases added). Like the discussion of the preferred embodiment, claim 13 acknowledges that these two steps include a directionality restriction. If the patentee wanted to import that same restriction—“follows behind”—into the “maintaining” limitation of claim 10, he could have used similar language. But he did not. The written description further confirms that the patentee understood how to describe the relationship between two clock signals in a manner that makes clear which clock signal leads or lags the other in phase. ’507 patent, col. 2, ll. 63–66 (“When the second phase detector 30 determines that the feedback clock signal CKF from the DLL 24 is behind the buffered input clock CKI within a 180˚ phase difference . . . .”). We decline to adopt a narrower construction in contravention of the plain language of the claims. Case: 19-1343 Document: 43 Page: 16 Filed: 04/06/2020 16 PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD. And, even if we were to determine that the above passage pertains to the “maintaining” limitation, it is well established that claims may be broader than described embodiments. See, e.g., Innogenetics, N.V. v. Abbott Labs., 512 F.3d 1363, 1370 (Fed. Cir. 2008).