Datasheet

Data Sheet ADM2491E
Rev. C | Page 15 of 16
TYPICAL APPLICATIONS
Figure 30 and Figure 31 show typical applications of the
ADM2491E in half-duplex and full-duplex RS-485 network
configurations. Up to 32 transceivers can be connected to the
RS-485 bus. To minimize reflections, the line must be terminated
at the receiving end in its characteristic impedance, and stub
lengths off the main line must be kept as short as possible. For
half-duplex operation, this means that both ends of the line
must be terminated because either end can be the receiving end.
NOTES
1. R
T
IS EQUAL TO THE CHARACTERISTIC IMPEDANCE OF THE CABLE.
2. ISOLATION NOT SHOWN.
06985-030
ADM2491E
RxD DE TxD
ABZY
ADM2491E
RxD DE TxD
ABZY
ADM2491EADM2491E
A
B
Z
Y
A
B
Z
Y
R1
R2
R
T
V
CC
R
D
R
D
R
D
R
D
R
T
RxD
DE
TxD
RxD
DE
TxD
MAXIMUM NUMBER OF TRANSCEIVERS ON BUS = 32
RE
RE
RE RE
Figure 30. ADM2491E Typical Half-Duplex RS-485 Network
06985-031
R
D
RxD
RE
TxD
DE
ADM2491E
ADM2491E
A
B
Z
Y
R
D
RxD TxDDE
A B Z Y
RE
R
D
RxD
TxD
DE
ADM2491E
MASTER SLAVE
SLAVE
A
B
Z
Y
RE
M
A
X
IMUM NUMBER OF NODES = 32
ADM2491E
R
D
RxD TxDDE
A B Z Y
RE
SLAVE
NOTES
1. R
T
IS EQUAL TO THE CHARACTERISTIC IMPEDANCE OF THE CABLE.
R
T
V
DD
R1
R2
R
T
V
DD
R1
R2
Figure 31. ADM2491E Typical Full -Duplex RS-485 Network