Datasheet

14
LTC1321/LTC1322/LTC1335
124V
CC
5V
1321/22/35 F13
120Ω
11
19
LTC1321
LTC1322
LTC1335
RX OUT
16
5V
10
9
8
7
6
12
15
14
RS485 I/O
EIA562 DR OUT
17
5V
18
13
V
EE
–5V
5V
0V
3
22
RX OUT
4
EIA562 RX IN (LTC1322/LTC1335 ONLY)
21
2
RX OUT
5
DR IN
DR ENABLE
DR IN
DR IN
20
EIA562 DR OUT (LTC1322/LTC1335 ONLY)
LTC1321/LTC1322 ONLY
EIA562 RX IN
V
DD
(LTC1321/LTC1322)
OR OE (LTC1335)
0.1µF
0.1µF
1
24
V
CC
5V
V
–

–12V
V
+

12V
1321/22/35 F14
120Ω
0.1µF
0.1µF
0.1µF
11
19
LTC1321
LTC1322
RX OUT
16
5V
10
9
8
7
6
12
15
14
RS485 I/O
*OPTIONAL
RS232 DR OUT
17
5V
Z3*
1N5246B
16V
18
13
V
EE
5V
0V
3
22
RX OUT
4
RS232 RX IN (LTC1322 ONLY)
21
2
RX OUT
5
DR IN
DR ENABLE
DR IN
DR IN
20
RS232 DR OUT (LTC1322 ONLY)
RS232 RX IN
V
DD
Z1
1N5229B
4.3V
Z2
1N5229B
4.3V
Figure 13. EIA562/RS485 Interfaces with ±5V Supplies
Figure 14. RS232/RS485 Interfaces with 5V, ±12V Supplies
LocalTalk and AppleTalk are registered trademarks of Apple Computer, Inc.
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 4µA
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
DD
and V
CC
pins
to be tied together and connected to 5V supply (Figure 13).
The V
DD
and V
CC
are connected internally and brought out
at V
CC
pin in the LTC1335. The unloaded outputs will
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
DD
and V
EE
supply voltages increased to provide the additional signal
swing. To meet RS232, V
DD
must be between 6.5V and
10V, and V
EE
must be between –6.5V and –10V. V
CC
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
DD
and V
EE
supply pins as shown in
Figure 14. An optional 16V Zener diode between V
CC
and
V
EE
is recommended to keep the maximum voltage be-
tween V
CC
and V
EE
within safe limits.
LocalTalk
®
/AppleTalk
®
Applications
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.
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