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...
