The AD5170 is a 256-position， two-time programmable， digital potentiometer1 that employs fuse link technology， giving users two opportunities to permanently program the resistance setting. For users who do not need to program the digital potentiometer setting in memory more than once， the OTP feature is a costeffective alternative to EEMEM. The AD5170 performs the same electronic adjustment function as mechanical potentiometers or variable resistors with enhanced resolution， solid-state reliability， and superior low temperature coefficient performance. The AD5170 is programmed using a 2-wire， I2 C?-compatible digital interface. Unlimited adjustments are allowed before permanently setting the resistance value， and there are two opportunities for permanent programming. During OTP activation， a permanent blow fuse command freezes the wiper position （analogous to placing epoxy on a mechanical trimmer）。 Unlike traditional OTP digital potentiometers， the AD5170 has a unique temporary OTP overwrite feature that allows for new adjustments even after the fuse is blown. However， the OTP setting is restored during subsequent power-up conditions. This feature allows users to treat these digital potentiometers as volatile potentiometers with a programmable preset. For applications that program the AD5170 at the factory， Analog Devices， Inc.， offers device programming software that runs on Windows NT?， Windows? 2000， and Windows XP operating systems. This software effectively replaces any external I2 C controllers， thus enhancing the time-to-market of the user’s systems.