ADLINK PCI-8158 - Manual (Page 35)

Signal Connections 25
Please note that the voltage across each differential pair of
encoder input signals (EA+, EA-), (EB+, EB-), and (EZ+, EZ-)
should be at least 3.5V. Therefore, the output current must be
observed when connecting to the encoder feedback or motor
driver feedback as not to over drive the source. The differential
signal pairs are converted to digital signals EA, EB, and EZ; then
feed to the motion control ASIC.
Below are examples of connecting the input signals with an exter-
nal circuit. The input circuit can be connected to an encoder or
motor driver if it is equipped with: (1) a differential line driver or (2)
an open collector output.
3.2.1 Connection to Line Driver Output
To drive the PCI-8158 encoder input, the driver output must pro-
vide at least 3.5V across the differential pairs with at least 8mA
driving capacity. The grounds of both sides must be tied together.
The maximum frequency is 4Mhz or more depends on wiring dis-
tance and signal conditioning.
3.2.2 Connection to Open Collector Output
To connect with an open collector output, an external power sup-
ply is necessary. Some motor drivers can provide the power
source. The connection between the PCI-8158, encoder, and the
power supply is shown in the diagram below. Note that an external
current limiting resistor R is necessary to protect the PCI-8158
input circuit. The following table lists the suggested resistor values
according to the encoder power supply.