SNLS144J June 2005 – January 2016 DS40MB200
PRODUCTION DATA.
NOTE
Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.
The DS40MB200 is a 2:1 MUX and 1:2 buffer that equalizes input data up to 4 Gbps and provides transmit pre-emphasis controls to improve overall signal reach. As a MUX buffer, the DS40MB200 is ideal for designs where there is a need for port sharing or redundancy as well as on-the-fly reorganization of routes and data connections.
A typical application for the DS40MB200 is shown in Figure 9 and Figure 10.
In a typical design, the DS40MB200 equalizes a short backplane trace on its input, followed by a longer trace at the DS40MB200 output. In this application example, a 25-inch FR4 coupled micro-strip board trace is used in place of the short backplane link. A block diagram of this example is shown in Figure 11.
The 25-inch microstrip board trace has approximately 6 dB of attenuation between 375 MHz and 1.875 GHz, representing closely the transmission loss of the short backplane transmission line. The 25-inch microstrip is connected between the pattern generator and the differential inputs of the DS40MB200 for AC measurements.
TRACE LENGTH | FINISHED TRACE WIDTH W | SEPARATION BETWEEN TRACES | DIELECTRIC HEIGHT H | DIELECTRIC CONSTANT εR | LOSS TANGENT |
---|---|---|---|---|---|
25 inches | 8.5 mil | 11.5 mil | 6 mil | 3.8 | 0.022 |
The length of the output trace may vary based on system requirements. In this example, a 40-inch FR4 trace with similar trace width, separation, and dielectric characteristics is placed at the DS40MB200 output.
As with any high-speed design, there are many factors which influence the overall performance. Following is a list of critical areas for consideration and study during design.
For optimal design, the DS40MB200 must be configured to route incoming data correctly as well as to provide the best signal quality. The following design procedures must be observed:
Figure 12 through Figure 17 show how the signal integrity varies at different places in the data path. These measured locations can be referenced back to the labeled points provided in Figure 11.
The source signal is a PRBS-7 pattern at 4 Gbps. For the long output traces, the eye after 40 inches of output FR4 trace is significantly improved by adding –9 dB of pre-emphasis.