LTC1321 LINER [Linear Technology], LTC1321 Datasheet - Page 14

• Manufacturer Part Number: LTC1321
• Description: RS232/EIA562/RS485 Transceivers
• Manufacturer: LINER [Linear Technology]

LB pin has a LOW logic state. The driver outputs are not
isolated from the external loads. This allows transmitter
verification under the loaded condition. An internal 4 A
current source pulls the LB pin HIGH if left open and
disables the loopback configuration.
EIA562/RS485 Applications
EIA562 and RS485 output levels are supported when
LTC1321/LTC1322/LTC1335 are powered from 5V sup-
plies. The LTC1321/LTC1322 require the V
to be tied together and connected to 5V supply (Figure 13).
The V
at V
swing from – 5V to 5V in EIA562 mode, and from 0V to 5V
in RS485 mode.
RS232/RS485 Applications
If true RS232-compatible outputs are required, the
LTC1321/LTC1322 may be used with the V
supply voltages increased to provide the additional signal
swing. To meet RS232, V
10V, and V
remains connected to 5V. If only 12V supplies are avail-
able, inexpensive Zener diodes (Z1 and Z2) may be con-
nected in series with V
Figure 14. An optional 16V Zener diode between V
V
tween V
LocalTalk
The LTC1321/LTC1322/LTC1335 can be used to provide
AppleTalk/LocalTalk-compatible signals in RS485 mode.
Figure 15 shows one half of an LTC1335 connected to an
LTC1320 AppleTalk transceiver in a typical LocalTalk
configuration. Figure 16 shows a typical direct-wire con-
nection with the LTC1335 as the DCE transceiver and the
LTC1320 as the DTE transceiver. The LTC1321/LTC1322/
LTC1335 RS485 mode is capable of meeting all AppleTalk
protocol specifications.
LTC1321/LTC1322/LTC1335
A
14
LocalTalk and AppleTalk are registered trademarks of Apple Computer, Inc.
EE
PPLICATI
CC
is recommended to keep the maximum voltage be-
DD
pin in the LTC1335. The unloaded outputs will
CC
and V
®
and V
/AppleTalk
EE
CC
must be between – 6.5V and – 10V. V
O
are connected internally and brought out
EE
within safe limits.
U
DD
S
®
Applications
and V
I FOR ATIO
DD
U
must be between 6.5V and
EE
supply pins as shown in
W
DD
and V
DD
U
and V
CC
CC
pins
and
CC
EE
V
–5V
V
V
5V
CC
5V
CC
EE
Figure 14. RS232/RS485 Interfaces with 5V, 12V Supplies
–12V
DR ENABLE
Figure 13. EIA562/RS485 Interfaces with 5V Supplies
V
–
0.1 F
0.1 F
RX OUT
RX OUT
RX OUT
Z2
1N5229B
4.3V
Z3*
1N5246B
16V
DR IN
DR IN
DR IN
V
EE
5V
5V
DR ENABLE
0.1 F
RX OUT
RX OUT
RX OUT
24
22
21
20
19
18
17
16
15
14
13
DR IN
DR IN
DR IN
5V
5V
0.1 F
LTC1321
LTC1322
LTC1335
20
19
21
18
17
24
22
16
15
14
13
*OPTIONAL
LTC1321
LTC1322
10
11
1
2
3
4
6
7
8
9
12
5
5V
0V
EIA562 DR OUT (LTC1322/LTC1335 ONLY)
EIA562 RX IN
EIA562 DR OUT
EIA562 RX IN (LTC1322/LTC1335 ONLY)
10
11
12
1
2
3
4
6
7
8
9
5
LTC1321/LTC1322 ONLY
V
OR OE (LTC1335)
DD
V
DD
(LTC1321/LTC1322)
120
5V
0V
RS232 DR OUT
RS232 DR OUT (LTC1322 ONLY)
RS232 RX IN
RS232 RX IN (LTC1322 ONLY)
RS485 I/O
120
RS485 I/O
12V
V
+
1321/22/35 F13
Z1
1N5229B
4.3V
0.1 F
1321/22/35 F14