Using InfiniiSim with Active Terminations
Application Notes
Many DDR memory driver measurements performed using real-time oscilloscopes need to use de-imbedding to relocate the measurement observation node or remove the effects of probe loading. However, most DDR memory devices don’t terminate their signal transmission lines to ground as InfiniiSim (Keysight’s de-embedding applications) expects, leading to DC errors in InfiniiSim’s transformed waveforms. This application note describes the DDR memory DC offset problem and why the error occurs. It also explains how to correct for the error and provides a procedure using waveform math functions to compute the correct response without the DC error. The application note presents a specific DDR5 measurement example that exhibits the offset error and its correction. Finally, a method to verify the InfiniiSim offset correction using Keysight's ADS (Advanced Design System) simulator application is presented and shown to accurately correct the specific DDR5 example’s DC offset error.