LTC1485
U
W
W
SWITCHI G TI E WAVEFOR S
3V
1.5V
RE
1.5V
LZ
f = 1MHz; t ≤ 10ns; t ≤ 10ns
r
f
0V
t
ZL
t
5V
RO
1.5V
OUTPUT NORMALLY LOW
OUTPUT NORMALLY HIGH
0.5V
0.5V
V
OL
V
OH
1.5V
RO
0V
1485 F08
t
ZH
t
HZ
Figure 8. Receiver Enable and Disable Times
O U
W
U
PPLICATI
A
S I FOR ATIO
Typical Application
ends with a resistor equal to their characteristic imped-
ance, typically 120Ω. The input impedance of a receiver is
typically20ktoGND, or0.6unitRS485load, soinpractice
50 to 60 transceivers can be connected to the same wires.
The optional shields around the twisted pair help reduce
unwanted noise, and are connected to GND at one end.
A typical connection of the LTC1485 is shown in Figure 9.
Two twisted pair wires connect up to 32 driver/receiver
pairs for half duplex data transmission. There are no
restrictions on where the chips are connected to the wires
and it isn’t necessary to have the chips connected at the
ends. However, the wires must be terminated only at the
LTC1485
1
LTC1485
1
RX
DX
RECEIVER
RX
DX
RECEIVER
2
3
2
3
7
4
4
DRIVER
120Ω
120Ω
DRIVER
8
LTC1485
1485 F09
1
2
3
RX
DX
RECEIVER
7
8
4
DRIVER
Figure 9. Typical Connection
7
Linear [ Linear ]
