By Shine Chung, Chairman of Attopsemi™ Technology Abstract: OTP stands for “One-Time Programmable”, a device that can only be programmed once to store data permanently but ideally read infinite times. Traditionally, testability has been an issue for OTP. Every OTP bit should be programmed to ensure programmability. However, if only a single bit is programmed, the OTP block can no longer be used. Patented by Attopsemi™, I-fuse™ is a revolutionary non-breaking fuse technology that can be reliably programmed by heat assisted electromigration below a break point. Any cell can be tested as programmable if the initial fuse resistance is low enough (e.g. 400 ohms) to generate enough heat for programming. The program voltage range can be tested and calibrated in a way that program yield can be predicted accurately. In I-fuse™ design, a pseudo-programmed state can be created by applying a low voltage programming during read, called Concurrent Low-Voltage Write Read (CLVWR). By combining the normal read and pseudo-programmed read, complex SRAM-like test patterns can be generated to fully test a complete I-fuse™ OTP macro with 100% fault coverage.