DDR Signal Quality Specifications

Various scenarios for the DDR Signals have been simulated to generate a set of layout guidelines.

Overshoot (or undershoot) is the absolute value of the maximum voltage above or below VSS. The overshoot/undershoot specifications limit transitions beyond specified maximum voltages or VSS due to the fast signal edge rates. The processor can be damaged by single and/or repeated overshoot or undershoot events on any input, output, or I/O buffer if the charge is large enough (that is, if the over/undershoot is great enough). Baseboard designs which meet signal integrity and timing requirements and which do not exceed the maximum overshoot or undershoot limits listed in Table: Processor I/O Overshoot/Undershoot Specifications will ensure reliable IO performance for the lifetime of the processor.