National Semiconductor DS25CP104, User Manual

Page: 11 / 36

DS25CP104EVK User Manual
Pre-Emphasis and Equalization Performance Testing
In some applications, data transmits over cables or long backplanes. The pre-emphasis
and equalization functions on the DS25CP104 help to compensate for loss of certain
media; hence the DS25CP104EVK has three lengths of stripline to test the pre-emphasis
and equalization functions.
1. Configure the test setup as shown in Figure 7; select the desired test channel,
lengths in Table 7.
2. Set the desired INn to OUTn drivers by selecting S00, S01, S10, S11, S20, S21,
S30, S31 according to Tables 1 – 4.
3. Select the PEn jumpers to 1 and the EQn jumpers to 1, according to Tables 5 and
6.
4. Apply + supply (3.3V typical) to the VDD and – supply (ground) to the VSS
connectors.
5. Connect a signal source (signal generator, data source, or an LVDS driver) to the
desired INn inputs on the board and adjust the signal parameters (VOH, VOL,
VCM) so that they comply with the device input recommendations.
6. Connect an oscilloscope to the selected OUTn outputs and view the output
signals with an oscilloscope with a bandwidth of at least 5 GHz.
50
Microstrip
L=4"
L=4"
L=4"
L=4"
TEST
CHANNEL
DS25CP104EVK
¼ DS25CP104
PATTERN
GENERATOR
OSCILLOSCOPE
50
Microstrip
50
Microstrip
50
Microstrip
TEST
CHANNEL
Figure 7 . Pre-emphasis and Equalization Performance Test Circuit
Page 11 of 17