Method to perform analog differential signal characterization using a signal eye in a data propagation system

Method to perform analog differential signal characterization using a signal eye in a data propagation system

Disclosed is a method for an algorithm to perform differential signal characterization using a signal eye in a data propagation system. Benefits include improved performance and an improved development environment.

Background

              With high-speed buses, interconnect technology, and I/O buffers, data propagation occurs with very little margin for error. Detailed descriptions of data signal integrity must be available to determine if receivers can capture data accurately. Simulation is required for development to design to requirement before production and increase yields significantly.  

              The conventional method defines the opening of one differential signal eye using two numbers, a height (volt) and a width (time). However, four points on the eye opening are selected to characterize the eye boundary. This approach has the potential of not accounting for the propagation effects in the output data.

General description

              The disclosed method is a differential signal characterization to determine if the signal quality is sufficient to enable the accurate capturing of logical data within the data eye, minimizing the bit error rate. The data for the analysis can be recorded at any point of the system where data capture is implemented. The source data for the bus/component can be generated using simulation of a data propagation system or it can be obtained through measurement in the lab environment. In the development of this concept, simulation of a high-speed interconnect was used to implement this methodology and formulate the resulting algorithm.

              The disclosed method provides a full description of the eye, giving a plot of all possible eye widths and related eye heights. All the eye boundary information is used to generate the eye window plot, taking into account the whole eye for defining the eye data. The full characterization of the eye provides more degrees of freedom to the circuit designers and provides better description of the eye. Instead of designing a circuit to a fixed specification of one height (voltage) and one width (time), the disclosed method enables the designer to select a certain height (volts) and determine if the eye plot would meet the timing (height) requirement.

              Trying to meet one specific requirement set by a pair of voltage and time numbers can make the design too tight. Due to the requirement to meet the given specification, the design can be over compensated resulting in higher cost. The disclosed approach provides more design accuracy and better design flexibility.

Advantages

              Some implementations of the disclosed structure and method provide one or more of the following advantages:

·        More detailed scan of the eye opening

·        More comprehensive characterization of the eye

·        Improved information to I/O and data capture circuit designers

·        Reduced risk of over or under design

·        Improved information about the impact of hig...