LTC1334
APPLICATI
C1
S I FOR ATIO
1
LTC1334
28
27 0.1µF
26
25
4
2
3
0.1µF
V
DD
0.1µF
INPUT A
K1A
120Ω
0.1µF
RX OUT
PORT 1
INTERFACE
5V
K1*
TX2A-5V
INPUT B
OUTPUT A
K1B
120Ω
OUTPUT B
360k
5
6
24
RX OUT
22
8
DR IN
SEL1
7
23
21
20
DR IN/ENABLE
LB
ON/OFF
RX OUT
FMMT619**
7.5k
TERM1
16
13
INPUT A
K2A
120Ω
PORT 2
INTERFACE
5V
K2*
TX2A-5V
INPUT B
OUTPUT A
K2B
120Ω
OUTPUT B
360k
FMMT619**
7.5k
12
11
17
RX OUT
19
9
DR IN
SEL2
10
14
18
15
DR IN/ENABLE
V
EE
LTC1334 • F12
0.1µF
TERM2 *AROMAT CORP (800) 276-6289
**ZETEX (516) 543-7100
Figure 12. Multiprotocol Interface
with Optional, Switchable Terminations
1/2 LTC1334
RX OUT
DR ENABLE
DR IN
5V
24
23
22
8
6
7
7 6
5 4
1/2
LTC1334
22 23
24 8
4
5
120Ω
120Ω
Figure 14. Typical Connection for RS485 Interface
12
U
C2
V
CC
5V
W
U
UO
Each receiver in the LTC1334 is designed to present one
unit load (5kΩ nominal for RS232 and 12kΩ minimum for
RS485) to the cable. Some RS485 and RS422 applications
call for terminations, but these are only necessary at two
nodes in the system and they must be disconnected when
operating in the RS232 mode. A relay is the simplest, low-
est cost method of switching terminations. In Figure 12
TERM1 and TERM2 select 120Ω terminations as needed.
If terminations are needed in all RS485/RS422 applica-
tions, no extra control signals are required; simply con-
nect TERM1 and TERM2 to SEL1 and SEL2.
Typical Applications
A typical RS232/EIA562 interface application is shown in
Figure 13 with the LTC1334.
A typical connection for a RS485 transceiver is shown in
Figure 14. A twisted pair of wires connects up to 32 drivers
and receivers for half duplex multipoint data transmission.
The wires must be terminated at both ends with resistors
equal to the wire’s characteristic impedance. An optional
shield around the twisted pair helps to reduce unwanted
noise and should be connected to ground at only one end.
1/2 LTC1334
DR IN
DR IN
RX OUT
RX OUT
19
18
17
16
9
LTC1334 • F13
1/2 LTC1334
11
10
12
RS232/
EIA562
LINES
4
5
6
7
24
25
22
23
8
RX OUT
RX OUT
DR IN
DR IN
13 INTERFACE
Figure 13. Typical Connection for RS232/EIA562 Interface
1/2 LTC1334
13
17
12
18
11
10
19
9
RX OUT
DR ENABLE
DR IN
5V
DR IN
RX OUT
DR ENABLE
5V
LTC1334 F14
LINER [ LINEAR TECHNOLOGY ]
