Texas Instruments SN65LVDS386EVM, Руководство пользователя

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SN65LVDS386EVM Operation
4-3
Operation
4.2 SN65LVDS386EVM Operation
Like the SN65LVDS387EVM, the SN65LVDS386EVM is shipped with all re-
quired components already installed on the board, and is ready for testing. For
the LVDS386, differential inputs need to be provided to simulate the differential
output-voltage levels (Vod is nominally 400 mV) and common-mode output-
voltage inputs (nominally 1.2 Vdc) of an LVDS driver. These inputs are easily
connected to the right edge P3-P7 LVDS side of the SN65LVDS386EVM. The
LVTTL output signals can be monitored using a scope probe connected direct-
ly to the P1/P2 connector pin.
As shipped, each LVDS input channel is terminated with 100-
Ω
resistors (R1
through R16) across the receiver inputs. These resistors are located on the
backside of the EVM near the input pins of the device. Each LVTTL output pin
is routed directly to the P1/P2 connector row. There are provisions on the
SN65LVDS386EVM to install a series resistor and a pulldown resistor. This al-
lows users to install a resistor divider on the output if required for testing the
device. But, as shipped, the series resistors (R17 through R32) have zero-ohm
resistors installed, and the pulldown resistors (R33 through R48) have no com-
ponents installed.
4.3 System Evaluation Using Both the SN65LVDS387EVM and
SN65LVDS386EVM
These EVMs has been designed to allow performance evaluation of both de-
vices when connected together. This allows users to perform tests using the
specific type and length of cable between the SN65LVDS387EVM and the
SN65LVDS386EVM. Users also has the option to install any specific connec-
tors and to use jumper wires to the BergStick

connectors. However, it is rec-
ommended that any jumper wires be kept as short as possible to minimize their
effect on system performance.
4.3.1 Point-to-Point Configuration
The majority of applications will have the outputs of the SN65LVDS387 driver
connected directly to an SN65LVDS386 receiver. This point-to-point configu-
ration can be used to perform higher-level system monitoring, such as chan-
nel-to-channel skew, crosstalk, and peak-to-peak jitter.
4.3.2 Multidrop Configuration
Using the SN65LVDS387EVM and SN65LVDS386EVM allows the perfor-
mance of multidrop tests. A multidrop configuration is defined as one in which
more than one receiver is connected to a single driver. There are many differ-
ent multidrop configurations that can be tested using both the SN65LVDS387
and SN65LVDS386EVM. Two possible configurations are shown in Figure
4–1. The termination resistors on the SN65LVDS386EVM will need to be re-
moved as required by the specific multidrop configuration.