LTC1344A
Software-Selectable
Cable Terminator
FEATURES
s
DESCRIPTION
The LTC
®
1344A features six software-selectable
multiprotocol cable terminators. Each terminator can be
configured as an RS422 (V.11) 100Ω 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.
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
Outputs Won’t Load the Line with Power Off
APPLICATIONS
s
s
s
Data Networking
CSU and DSU
Data Routers
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATION
DTE or DCE Multiprotocol Serial Interface with DB-25 Connector
LL
CTS
DSR
DCD
DTR
RTS
RXD
RXC
TXC
SCTE
TXD
Daisy-Chained Control Outputs
LTC1544
D4
R4
R3
R2
R1
D3
D2
D1
R3
R2
R1
LTC1543
D3
D2
D1
18
LL A (141)
13 5
CTS B
CTS A (106)
10 8
DSR B
DSR A (109)
22 6
DCD B
DCD A (107)
23 20 19 4
DTR B
DTR A (108)
RTS B
RTS A (105)
SHIELD (101)
1
SG (102)
7
16 3
RXD B
RXD A (104)
9
RXC B
17
RXC A (115)
12 15 11 24 14
SCTE B
SCTE A (113)
TXD B
TXD A (103)
TXC B
TXC A (114)
DB-25 CONNECTOR
U
U
U
LTC1344A
2
1344A TA01
1
LTC1344A
ABSOLUTE
MAXIMUM
RATINGS
(Note 1)
PACKAGE/ORDER I FOR ATIO
TOP VIEW
M0
V
EE
R1C
R1B
R1A
R2A
R2B
R2C
R3A
1
2
3
4
5
6
7
8
9
24 M1
23 M2
22 DCE/DTE
21 LATCH
20 R6B
19 R6A
18 R5A
17 R5B
16 R4A
15 R4B
14 V
CC
13 GND
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
ORDER PART
NUMBER
LTC1344ACG
LTC1344AIG
R3B 10
R3C 11
GND 12
G PACKAGE
24-LEAD PLASTIC SSOP
T
JMAX
= 150°C,
θ
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.
SYMBOL
Supplies
I
CC
R
V.35
Supply Current
Differential Mode Impedance
Common Mode Impedance
All Digital Pins = GND or V
CC
All Loads (Figure 1), – 2V
≤
V
CM
≤
2V (Commercial)
All Loads (Figure 2), – 2V
≤
V
CM
≤
2V (Commercial)
All Loads (Figure 1), – 2V
≤
V
CM
≤
2V (Industrial)
All Loads (Figure 2), – 2V
≤
V
CM
≤
2V (Industrial)
R
V.11
Differential Mode Impedance
All Loads (Figure 1), V
CM
= 0V (Commercial)
All Loads (Figure 1), – 7V
≤
V
CM
≤
7V (Commercial)
All Loads (Figure 1), V
CM
= 0V (Industrial)
All Loads (Figure 1), – 7V
≤
V
CM
≤
7V (Industrial)
I
LEAK
V
IH
V
IL
I
IN
High Impedance Leakage Current
Input High Voltage
Input Low Voltage
Input Current
All Loads, – 7V
≤
V
CM
≤
7V
All Logic Input Pins
All Logic Input Pins
All Logic Input Pins
Logic Inputs
q
q
q
q
PARAMETER
CONDITIONS
MIN
TYP
0.4
MAX
1.0
110
165
115
170
110
115
±50
UNITS
mA
Ω
Ω
Ω
Ω
Ω
Ω
Ω
Ω
µA
V
Terminator Pins
q
q
q
q
q
q
q
90
135
90
130
100
100
95
100
104
153
104
153
104
104
104
104
±1
2
0.8
±10
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.
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.
2
U
V
µA
W
U
U
W W
W
LTC1344A
TYPICAL PERFORMANCE CHARACTERISTICS
V.11 or V.35 Differential Mode
Impedance vs Temperature
120
DIFFERENTIAL MODE IMPEDANCE (Ω)
DIFFERENTIAL MODE IMPEDANCE (Ω)
108
115
V
CM
= –7V
106
110
V
CM
= –2V
V
CM
= 0V
DIFFERENTIAL MODE IMPEDANCE (Ω)
105
V
CM
= 7V
100
–40 –20
0
20
40
60
80
100
1344 G01
TEMPERATURE (°C)
V.11 or V.35 Differential Mode
Impedance vs Negative Supply
Voltage (V
EE
)
105
165
T
A
= 25°C
COMMON MODE IMPEDANCE (Ω)
160
DIFFERENTIAL MODE IMPEDANCE (Ω)
COMMON MODE IMPEDANCE (Ω)
104
103
– 5.4
– 5.2
– 5.0
– 4.8
V
EE
VOLTAGE (V)
– 4.6
1344 G04
V.35 Common Mode Impedance
vs Supply Voltage (V
CC
)
153
T
A
= 25°C
154
COMMON MODE IMPEDANCE (Ω)
COMMON MODE IMPEDANCE (Ω)
SUPPLY CURRENT (µA)
152
151
4.6
4.8
5.0
5.2
V
CC
VOLTAGE (V)
5.4
1344 G07
U W
V.11 or V.35 Differential Mode
Impedance vs Common Mode
Voltage
105
T
A
= 25°C
V.11 or V.35 Differential Mode
Impedance vs Supply Voltage
(V
CC
)
T
A
= 25°C
104
104
102
100
103
–8
–6
– 4 –2
0
2
4
6
COMMON MODE VOLTAGE (V)
8
4.6
4.8
5.0
5.2
V
CC
VOLTAGE (V)
5.4
1344 G03
1344 G02
V.35 Common Mode Impedance
vs Temperature
158
V.35 Common Mode Impedance
vs Common Mode Voltage
T
A
= 25°C
156
V
CM
= –2V
155
154
150
V
CM
= 2V
145
– 40 –20
V
CM
= 0V
152
0
60
40
20
TEMPERATURE (°C)
80
100
1344 G05
150
–2
0
–1
1
COMMON MODE VOLTAGE (V)
2
1344 G06
V.35 Common Mode Inpedance
vs Negative Supply Voltage (V
EE
)
500
T
A
= 25°C
Supply Current vs Temperature
153
420
152
340
151
260
150
– 5.4
– 5.2
– 4.8
– 5.0
V
EE
VOLTAGE (V)
– 4.6
1344 G08
180
–40 –20
0
40
60
20
TEMPERATURE (°C)
80
100
1344 G09
3
LTC1344A
PIN FUNCTIONS
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 1µF 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
C
A
R1
51.5Ω
Ω
S1
ON
S2
OFF
R2
51.5Ω
R3
124Ω
LTC1344A
B
V
±7V
OR
±2V
1344 F01
Figure 1. Differential V.11 or V.35 Impedance Measurement
4
U
U
U
C
LTC1344A
R1
51.5Ω
S1
ON
A, B
R2
51.5Ω
Ω
V
±2V
S2
ON
R3
124Ω
1344 F02
Figure 2. V.35 Common Mode Impedance Measurement
LTC1344A
ODE SELECTIO
X
0
1
0
1
0
1
0
1
0
1
X
X
LTC1344A
MODE NAME
V.10/RS423
RS530A
RS530
X.21
V.35
RS449/V.36
V.28/RS232
No Cable
DCE/DTE
X = don’t care, 0 = logic low, 1 = logic high
A
R1
51.5Ω
S1
ON
S2
OFF
R2
51.5Ω
B
V.11 Mode
U
M2
0
0
0
0
0
0
0
1
1
1
1
1
1
M1
0
0
0
1
1
1
1
0
0
0
0
1
1
M0
0
1
1
0
0
1
1
0
0
1
1
0
1
R1
Z
Z
Z
Z
Z
Z
Z
V.35
V.35
Z
Z
Z
V.11
R2
Z
Z
Z
Z
Z
Z
Z
V.35
V.35
Z
Z
Z
V.11
R3
Z
Z
Z
Z
Z
Z
Z
Z
V.35
Z
Z
Z
V.11
R4
Z
V.11
Z
V.11
Z
V.11
Z
V.35
Z
V.11
Z
Z
V.11
R5
Z
V.11
V.11
V.11
V.11
V.11
V.11
V.35
V.35
V.11
V.11
Z
V.11
R6
Z
V.11
V.11
V.11
V.11
V.11
V.11
V.35
V.35
V.11
V.11
Z
V.11
C
LTC1344A
A
R1
51.5Ω
S1
ON
S2
ON
R2
51.5Ω
B
B
C
LTC1344A
A
R1
51.5Ω
S1
OFF
S2
OFF
R2
51.5Ω
C
LTC1344A
R3
124Ω
R3
124Ω
R3
124Ω
W
V.35 Mode
High-Z Mode
1344 F03
Figure 3. LTC1344A Modes
5
