I have a SigXplorer simulation showing overshoot at the die level for a mobile DDR (1.8V) device driven by a fairly new ARM11 device that violates the overshoot specification fr the memory. However, the package pin shows no specific overshoot problem. The trace length is less than 1/2 inch and the speed is 133MHz. The trace is controlled impedance. According to the memory vendor, they say their specification is for the waveform at the package pin. But according to the CPU vendor and a high speed design consultant, they say that the signal performance at the die is also important.Originally posted in cdnusers.org by fitzdean
So, who do I believe?
The simulation only fails the overshoot specification when the Simulation Modes is set to FTS Mode: Fast. Typical and slow are fine. Attached is the printout from the simulation. Feel free
to email me if you have a definitive answer. Thanks in advance.