LTC1321IS View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC1321IS' PDF : 20 Pages View PDF
LTC1321/LTC1322/LTC1335
APPLICATI S I FOR ATIO
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 VDD and VCC pins
to be tied together and connected to 5V supply (Figure 13).
The VDD and VCC are connected internally and brought out
at VCC pin in the LTC1335. The unloaded outputs will
swing from – 5V to 5V in EIA562 mode, and from 0V to 5V
in RS485 mode.
VCC
24
5V
0.1µF
RX OUT
22
21
DR ENABLE
20
DR IN
19
5V
5V 18
DR IN 17
16
DR IN
15
RX OUT
14
RX OUT
VEE
13
–5V
0.1µF
LTC1321
LTC1322
LTC1335
LTC1321/LTC1322 ONLY
1
VDD (LTC1321/LTC1322)
2
OR OE (LTC1335)
3
120Ω RS485 I/O
4
5
6
5V
7 0V
8 EIA562 DR OUT
9 EIA562 DR OUT (LTC1322/LTC1335 ONLY)
10 EIA562 RX IN
11
EIA562 RX IN (LTC1322/LTC1335 ONLY)
12
1321/22/35 F13
Figure 13. EIA562/RS485 Interfaces with ±5V Supplies
RS232/RS485 Applications
If true RS232-compatible outputs are required, the
LTC1321/LTC1322 may be used with the VDD and VEE
supply voltages increased to provide the additional signal
swing. To meet RS232, VDD must be between 6.5V and
10V, and VEE must be between – 6.5V and – 10V. VCC
remains connected to 5V. If only ±12V supplies are avail-
able, inexpensive Zener diodes (Z1 and Z2) may be con-
nected in series with VDD and VEE supply pins as shown in
Figure 14. An optional 16V Zener diode between VCC and
VEE is recommended to keep the maximum voltage be-
tween VCC and VEE 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.
VCC
24
5V
0.1µF
RX OUT
22
21
DR ENABLE
20
DR IN
Z3*
1N5246B
16V
19
5V
5V 18
DR IN 17
DR IN 16
15
RX OUT
RX OUT 14
VEE
13
Z2
1N5229B
4.3V
V–
–12V
0.1µF
LTC1321
LTC1322
*OPTIONAL
1 VDD
2
3
V+
12V
Z1
1N5229B
4.3V
0.1µF
120Ω RS485 I/O
4
5
6 5V
7 0V
8 RS232 DR OUT
9 RS232 DR OUT (LTC1322 ONLY)
10 RS232 RX IN
11
RS232 RX IN (LTC1322 ONLY)
12
1321/22/35 F14
Figure 14. RS232/RS485 Interfaces with 5V, ±12V Supplies
LocalTalk and AppleTalk are registered trademarks of Apple Computer, Inc.
14
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