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1
LTC1344A
Software-Selectable
Cable Terminator
Daisy-Chained Control Outputs
TYPICAL APPLICATIO
N
U
DTE or DCE Multiprotocol Serial Interface with DB-25 Connector
D2
D1
LTC1544
RTS
DTR
DSR
DCD
CTS
D3
R2
R1
R4
R3
D2
LTC1543
LL
TXD
SCTE
TXC
RXC
RXD
2
14
24
11
15
12
17
9
3
1
4
19
20
6
23
22
5
13
8
10
18
7
16
1344A TA01
LTC1344A
D3
R2
R1
R3
D1
TXD A (103)
TXD B
SCTE A (113)
SCTE B
RXC A (115)
RXC B
RXD A (104)
RXD B
RTS A (105)
RTS B
DTR A (108)
DTR B
CTS A (106)
CTS B
LL A (141)
SG (102)
SHIELD (101)
DB-25 CONNECTOR
TXC A (114)
TXC B
DCD A (107)
DCD B
DSR A (109)
DSR B
D4
s
Data Networking
s
CSU and DSU
s
Data Routers
APPLICATIO
N
S
U
, LTC and LT are registered trademarks of Linear Technology Corporation.
FEATURES
s
Software-Selectable Cable Termination for:
RS232 (V.28)
RS423 (V.10)
RS422 (V.11)
RS485
RS449
EIA530
EIA530-A
V.35
V.36
X.21
s
Outputs Won't Load the Line with Power Off
The LTC
1344A features six software-selectable
multiprotocol cable terminators. Each terminator can be
configured as an RS422 (V.11) 100
minimum differen-
tial load, V.35 T-network load or an open circuit for use
with RS232 (V.28) or RS423 (V.10) transceivers that
provide their own termination. When combined with the
LTC1543 and LTC1544, the LTC1344A forms a complete
software-selectable multiprotocol serial port. A data bus
latch feature allows sharing of the select lines between
multiple interface ports.
The LTC1344A is similar to the LTC1344 except for a
difference in the Mode Selection table.
The LTC1344A is available in a 24-lead SSOP.
DESCRIPTIO
N
U
2
LTC1344A
ABSOLUTE
M
AXI
M
U
M
RATINGS
W
W
W
U
W
U
U
PACKAGE/ORDER I FOR ATIO
ORDER PART
NUMBER
LTC1344ACG
LTC1344AIG
1
2
3
4
5
6
7
8
9
10
11
12
TOP VIEW
G PACKAGE
24-LEAD PLASTIC SSOP
24
23
22
21
20
19
18
17
16
15
14
13
M0
V
EE
R1C
R1B
R1A
R2A
R2B
R2C
R3A
R3B
R3C
GND
M1
M2
DCE/DTE
LATCH
R6B
R6A
R5A
R5B
R4A
R4B
V
CC
GND
T
JMAX
= 150
C,
JA
= 100
C/W
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
V
CC
= 5V
5%, V
EE
= 5V
5%, T
A
= T
MIN
to T
MAX
(Notes 2, 3) unless otherwise noted.
(Note 1)
Positive Supply Voltage (V
CC
) ................................... 7V
Negative Supply Voltage (V
EE
) ........................... 13.2V
Input Voltage
(Logic Inputs) .................... (V
EE
0.3V) to (V
CC
+ 0.3V)
Input Voltage (Load Inputs) ..................................
18V
Power Dissipation .............................................. 600mW
Operating Temperature Range
LTC1344AC ............................................ 0
C to 70
C
LTC1344AI ......................................... 40
C to 85
C
Storage Temperature Range ................ 65
C to 150
C
Lead Temperature (Soldering, 10 sec)................. 300
C
Note 2: All currents into device pins are positive; all currents out of device
pins are negative. All voltages are reference to ground unless otherwise
specified.
Note 3: All typicals are given at V
CC
= 5V, V
EE
= 5V, T
A
= 25
C.
The
q
denotes specifications which apply over the full operating
temperature range.
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Supplies
I
CC
Supply Current
All Digital Pins = GND or V
CC
q
0.4
1.0
mA
Terminator Pins
R
V.35
Differential Mode Impedance
All Loads (Figure 1), 2V
V
CM
2V (Commercial)
q
90
104
110
Common Mode Impedance
All Loads (Figure 2), 2V
V
CM
2V (Commercial)
q
135
153
165
All Loads (Figure 1), 2V
V
CM
2V (Industrial)
q
90
104
115
All Loads (Figure 2), 2V
V
CM
2V (Industrial)
q
130
153
170
R
V.11
Differential Mode Impedance
All Loads (Figure 1), V
CM
= 0V (Commercial)
q
100
104
110
All Loads (Figure 1), 7V
V
CM
7V (Commercial)
100
104
All Loads (Figure 1), V
CM
= 0V (Industrial)
q
95
104
115
All Loads (Figure 1), 7V
V
CM
7V (Industrial)
100
104
I
LEAK
High Impedance Leakage Current
All Loads, 7V
V
CM
7V
q
1
50
A
Logic Inputs
V
IH
Input High Voltage
All Logic Input Pins
q
2
V
V
IL
Input Low Voltage
All Logic Input Pins
q
0.8
V
I
IN
Input Current
All Logic Input Pins
q
10
A
3
LTC1344A
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
V.11 or V.35 Differential Mode
Impedance vs Common Mode
Voltage
TEMPERATURE (
C)
40
DIFFERENTIAL MODE IMPEDANCE (
)
20
1344 G01
110
105
20
0
40
100
120
115
60
80
100
V
CM
= 7V
V
CM
= 2V
V
CM
= 0V
V
CM
= 7V
V
CC
VOLTAGE (V)
103
DIFFERENTIAL MODE IMPEDANCE (
)
104
105
1344 G03
4.6
4.8
5.0
5.2
5.4
T
A
= 25
C
COMMON MODE VOLTAGE (V)
8
DIFFERENTIAL MODE IMPEDANCE (
)
108
6
1344 G02
106
104
100
6
4
2
0
2
4
8
102
T
A
= 25
C
V.11 or V.35 Differential Mode
Impedance vs Temperature
V.35 Common Mode Impedance
vs Supply Voltage (V
CC
)
V.35 Common Mode Inpedance
vs Negative Supply Voltage (V
EE
)
V
CC
VOLTAGE (V)
151
COMMON MODE IMPEDANCE (
)
152
153
1344 G07
4.6
4.8
5.0
5.2
5.4
T
A
= 25
C
V
EE
VOLTAGE (V)
5.4
COMMON MODE IMPEDANCE (
)
153
154
4.6
1344 G08
152
151
150
5.2
5.0
4.8
T
A
= 25
C
Supply Current vs Temperature
TEMPERATURE (
C)
40
SUPPLY CURRENT (
A)
500
420
340
260
180
20
1344 G09
20
0
40
60
80
100
V.11 or V.35 Differential Mode
Impedance vs Negative Supply
Voltage (V
EE
)
TEMPERATURE (
C)
40
COMMON MODE IMPEDANCE (
)
20
1344 G05
155
150
20
0
40
145
165
160
60
80
100
V
CM
= 2V
V
CM
= 2V
V
CM
= 0V
COMMON MODE VOLTAGE (V)
2
COMMON MODE IMPEDANCE (
)
154
156
2
1344 G06
152
150
1
0
1
158
T
A
= 25
C
V.35 Common Mode Impedance
vs Temperature
V.35 Common Mode Impedance
vs Common Mode Voltage
V
EE
VOLTAGE (V)
103
DIFFERENTIAL MODE IMPEDANCE (
)
104
105
1344 G04
5.4
5.2
5.0
4.8
4.6
T
A
= 25
C
V.11 or V.35 Differential Mode
Impedance vs Supply Voltage
(V
CC
)
4
LTC1344A
PI
N
FU
N
CTIO
N
S
U
U
U
M0 (Pin 1): TTL Level Mode Select Input. The data on M0
is latched when LATCH is high.
V
EE
(Pin 2): Negative Supply Voltage Input. Can connect
directly to the LTC1543 V
EE
pin. Connect a 1
F capacitor
to ground.
R1C (Pin 3): Load 1 Center Tap.
R1B (Pin 4): Load 1 Node B.
R1A (Pin 5): Load 1 Node A.
R2A (Pin 6): Load 2 Node A.
R2B (Pin 7): Load 2 Node B.
R2C (Pin 8): Load 2 Center Tap.
R3A (Pin 9): Load 3 Node A.
R2B (Pin 10): Load 2 Node B.
R3C (Pin 11): Load 3 Center Tap.
GND (Pin 12): Ground Connection for Load 1 to Load 3.
GND (Pin 13): Ground Connection for Load 4 to Load 6.
V
CC
(Pin 14): Positive Supply Input. 4.75V
V
CC
5.25V.
R4B (Pin 15): Load 4 Node B.
R4A (Pin 16): Load 4 Node A.
R5B (Pin 17): Load 5 Node B.
R5A (Pin 18): Load 5 Node A.
R6A (Pin 19): Load 6 Node A.
R6B (Pin 20): Load 6 Node B.
LATCH (Pin 21): TTL Level Logic Signal Latch Input. When
LATCH is low the input buffers on M0, M1, M2 and DCE/
DTE are transparent. When LATCH is high the logic pins
are latched into their respective input buffers. The data
latch allows the select lines to be shared between multiple
I/O ports.
DCE/DTE (Pin 22): TTL Level Mode Select Input. DCE
mode is selected when high and DTE mode when low. The
data on DCE/DTE is latched when LATCH is high.
M2 (Pin 23): TTL Level Mode Select Input 1. The data on
M2 is latched when LATCH is high.
M1 (Pin 24): TTL Level Mode Select Input 2. The data on
M1 is latched when LATCH is high.
TEST CIRCUITS
R1
51.5
R2
51.5
2V
1344 F02
R3
124
S2
ON
S1
ON
C
V
A, B
LTC1344A
R1
51.5
R2
51.5
7V OR
2V
1344 F01
R3
124
S2
OFF
S1
ON
C
V
A
B
LTC1344A
Figure 2. V.35 Common Mode Impedance Measurement
Figure 1. Differential V.11 or V.35 Impedance Measurement
5
LTC1344A
LTC1344A
MODE NAME
DCE/DTE
M2
M1
M0
R1
R2
R3
R4
R5
R6
V.10/RS423
X
0
0
0
Z
Z
Z
Z
Z
Z
RS530A
0
0
0
1
Z
Z
Z
V.11
V.11
V.11
1
0
0
1
Z
Z
Z
Z
V.11
V.11
RS530
0
0
1
0
Z
Z
Z
V.11
V.11
V.11
1
0
1
0
Z
Z
Z
Z
V.11
V.11
X.21
0
0
1
1
Z
Z
Z
V.11
V.11
V.11
1
0
1
1
Z
Z
Z
Z
V.11
V.11
V.35
0
1
0
0
V.35
V.35
Z
V.35
V.35
V.35
1
1
0
0
V.35
V.35
V.35
Z
V.35
V.35
RS449/V.36
0
1
0
1
Z
Z
Z
V.11
V.11
V.11
1
1
0
1
Z
Z
Z
Z
V.11
V.11
V.28/RS232
X
1
1
0
Z
Z
Z
Z
Z
Z
No Cable
X
1
1
1
V.11
V.11
V.11
V.11
V.11
V.11
X = don't care, 0 = logic low, 1 = logic high
ODE SELECTIO
W U
R1
51.5
R2
51.5
R3
124
S2
OFF
S1
ON
V.11 Mode
V.35 Mode
High-Z Mode
A
B
R1
51.5
R2
51.5
R3
124
S2
ON
S1
ON
A
B
R1
51.5
R2
51.5
1344 F03
R3
124
A
B
S2
OFF
S1
OFF
C
C
C
LTC1344A
LTC1344A
LTC1344A
Figure 3. LTC1344A Modes
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