Richtek Technology Corporation v. uPI Semiconductor Corporation, 3:09-cv-05659

Richtek owns U.S. Patent No. 7,315,190 (DC-DC power controller technology); application filed June 2006, inventor Isaac Chen.
Richtek sued uPI in Dec. 2009 and also filed an ITC complaint the same day; ITC discovery and USPTO reexamination/stays delayed district litigation.
In November 2010 Richtek served infringement contentions asserting a June 16, 2006 priority date. Chen testified in the ITC that conception occurred in April 2006.
After USPTO reexamination, uPI obtained leave (in June 2016) to amend its invalidity contentions to add June 2006 prior art; parties treated ITC discovery as produced here.
On July 14, 2016 (shortly before fact discovery closed), Richtek moved to amend its infringement contentions to: (1) assert an earlier (April 2006) priority date, (2) identify five additional Richtek products that practice the patent, and (3) delete contentions as to defendants already dismissed by settlement.
uPI opposed the first two amendments; the court evaluated the motion under Patent Local Rule 3-6 (good cause/diligence and undue prejudice standard).

Issue	Plaintiff's Argument	Defendant's Argument	Held
Assert earlier priority date (April 2006)	April 2006 conception was revealed by Chen's ITC deposition; uPI cannot be prejudiced and the earlier date became relevant after uPI amended invalidity contentions	Believed amendment is untimely and prejudicial; Richtek should have disclosed earlier date in initial contentions	Denied — Richtek lacked diligence; should have asserted April 2006 earlier; no good cause shown
Identify additional Richtek products	Obliged to supplement disclosures to identify five more Richtek products that practice the claims	Opposed as untimely and lacking specificity; no explanation of purpose or diligence	Denied — motion lacked diligence, failed to describe products, and failed to show good cause
Remove contentions about dismissed defendants	N/A (move to delete contentions after those defendants settled/dismissed)	No opposition	Granted — amendment simplifies issues and was timely (filed promptly after dismissals)

O2 Micro Int’l Ltd. v. Monolithic Power Sys., Inc., 467 F.3d 1355 (Fed. Cir. 2006) (establishes the Patent Local Rules good-cause inquiry balancing diligence and prejudice)