IC-HF Datasheet, PDF (23/36 Pages) IC-Haus GmbH – 6-CH. ENCODER LINK, RS-422 DRIVER/RECEIVER

iC-HF
preliminary
6-CH. ENCODER LINK, RS-422 DRIVER/RECEIVER
RS422 Input
Qi
16k9
Xi
+
Rt
-
NQi
16k9
120
Figure 26: RS-422 receiver with external resistors
Rev C1, Page 23/36
Unused/open RS-422 input pins
To avoid oscillations on open or unused pins a stable
state is recommended. Unused or open RS-422 input
pins can be to be connected to a stable voltage. The
voltage of the positive and negative input pin needs
to be bigger than the input hysteresis. In the case
of unused input pins the Qi and NQi pins should be
connected to field sided, different, stable input voltages
like VDD and GND.
iC-HF allows RS-422 communication up to 10 MHz. At
high frequencies the performance can be improved by
using 1 pF capacitors parallel with each external resistor
(excluding the bus termination resistor). Some designs
do provide such similar capacity already by layout.
Example for stable input voltages on unused/open
pins:
• Qi = VDD
• NQi = GND