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1
LTC1349
5V Low Power RS232
3-Driver/5-Receiver Transceiver
with 2 Receivers Active
in SHUTDOWN
U
A
O
PPLICATI
TYPICAL
Quiescent and SHUTDOWN Supply Current
vs Temperature
S
FEATURE
D
U
ESCRIPTIO
s
Low Supply Current: 300
A
s
Two Receivers Kept Alive in SHUTDOWN
s
ESD Protection Over
10kV
s
Operates from a Single 5V Supply
s
Uses Small Capacitors: 0.1
F
s
Operates to 120k Baud
s
Three-State Outputs Are High Impedance When Off
s
Output Overvoltage Does Not Force Current
Back into Supplies
s
RS232 I/O Lines Can Be Forced to
25V
Without Damage
s
Pin Compatible with LT1137A and LT1237
s
Flowthrough Architecture
The LTC1349 is a 3-driver/ 5-receiver RS232 transceiver
with very low supply current. In the no load condition, the
supply current is only 300
A. The charge pump only
requires four 0.1
F capacitors.
In SHUTDOWN mode, two receivers are kept alive and the
supply current is 35
A. All RS232 outputs assume a high
impedance state in SHUTDOWN and with the power off.
The LTC1349 is fully compliant with all data rate and
overvoltage RS232 specifications. The transceiver can
operate up to 120k baud with a 2500pF, 3k
load. Both
driver outputs and receiver inputs can be forced to
25V
without damage, and can survive multiple
10kV ESD
strikes.
U
S
A
O
PPLICATI
s
Notebook Computers
s
Palmtop Computers
TEMPERATURE (C)
QUIESCENT CURRENT (
A)
1200
1000
800
600
400
200
0
20
40
60
LTC1349 TA02
80
0
40
60
50
40
30
20
10
0
SHUTDOWN CURRENT (
A)
QUIESCENT
CURRENT
SHUTDOWN
CURRENT
TEST CONDITION:
V
CC
= 5V, ALL DRIVER INPUTS TIED TO V
CC
.
20
100
3-Drivers/5-Receivers with SHUTDOWN
LTC1349 TA01
V
CC
C1
0.1
F
LTC1349
1
2
3
4
5
6
7
8
9
10
11
12
13
14
DRIVER 1 OUT
RX1 IN
DRIVER 2 OUT
RX2 IN
RX3 IN
RX4 IN
DRIVER 3 OUT
RX5 IN
ON/OFF
NC
28
27
26
25
24
23
22
21
20
19
18
17
16
15
C3
0.1
F
DRIVER 1 IN
RX1 OUT
DRIVER 2 IN
RX2 OUT
RX3 OUT
RX4 OUT
DRIVER 3 IN
RX5 OUT
GND
NC
NC
V
V
+
C2
0.1
F
C4
0.1
F
2
LTC1349
LTC1349CG
LTC1349CN
LTC1349CS
LTC1349IG
LTC1349IN
LTC1349IS
A
U
G
W
A
W
U
W
A
R
BSOLUTE
XI
TI
S
W
U
U
PACKAGE/ORDER I FOR ATIO
ORDER PART
NUMBER
Supply Voltage (V
CC
) ................................................ 6V
Input Voltage
Driver ....................................... 0.3V to V
CC
+ 0.3V
Receiver ............................................... 25V to 25V
On/Off Pin .................................. 0.3V to V
CC
+ 0.3V
Output Voltage
Driver .................................................... 25V to 25V
Receiver .................................... 0.3V to V
CC
+ 0.3V
Short Circuit Duration
V
+
................................................................... 30 sec
V
................................................................... 30 sec
Driver Output .............................................. Indefinite
Receiver Output .......................................... Indefinite
Operating Temperature Range
Commercial (LTC1349C) ........................ 0
C to 70
C
Industrial (LTC1349I) ........................ 40
C to 85
C
Storage Temperature Range ................ 65
C to 150
C
Lead Temperature (Soldering, 10 sec) ................. 300
C
ELECTRICAL C
C
HARA TERISTICS
C
D
V
CC
= 5V, C1 = C2 = C3 = C4 = 0.1
F, unless otherwise noted.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
V
+
V
CC
C1
+
C1
DR1 OUT
RX1 IN
DR2 OUT
RX2 IN
RX3 IN
RX4 IN
DR3 OUT
RX5 IN
ON/OFF
NC
28
27
26
25
24
23
22
21
20
19
18
17
16
15
V
C2
+
C2
DR1 IN
RX1 OUT
DR2 IN
RX2 OUT
RX3 OUT
RX4 OUT
DR3 IN
RX5 OUT
GND
NC
NC
N PACKAGE
28-LEAD PLASTIC DIP
TOP VIEW
S PACKAGE
28-LEAD PLASTIC SOL
G PACKAGE
28-LEAD SSOP
T
JMAX
= 125
C,
JA
= 96
C/W (G)
T
JMAX
= 125
C,
JA
= 56
C/W (N)
T
JMAX
= 125
C,
JA
= 85
C/W (S)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Any Driver
Output Voltage Swing
3k to GND
Positive
q
5.0
7.0
V
Negative
q
5.0
6.5
V
Logic Input Voltage Level
Input Low Level (V
OUT
= High)
q
1.4
0.8
V
Input High Level (V
OUT
= Low)
q
2.0
1.4
V
Logic Input Current
V
IN
= 5V
q
5
A
V
IN
= 0V
q
5
A
Output Short-Circuit Current
V
OUT
= 0V
12
mA
Output Leakage Current
SHUTDOWN, V
OUT
=
20V (Note 3)
q
10
500
A
Any Receiver
Input Voltage Thresholds
Input Low Threshold
q
0.8
1.3
V
Input High Threshold
q
1.7
2.4
V
Hysteresis
q
0.1
0.4
1.0
V
Input Resistance
10V
V
IN
10V
3
5
7
k
Output Voltage
Output Low, I
OUT
= 1.6mA (V
CC
= 5V)
q
0.2
0.4
V
Output High, I
OUT
= 160
A (V
CC
= 5V)
q
3.5
4.8
V
Output Short-Circuit Current
Sinking Current, V
OUT
= V
CC
15
40
mA
Output Leakage Current
SHUTDOWN, 0
V
OUT
V
CC
(Note 3)
q
1
10
A
Power Supply Generator
V
+
Output Voltage
I
OUT
= 0mA
8.0
V
I
OUT
= 12mA
7.5
V
V
Output Voltage
I
OUT
= 0mA
8.0
V
I
OUT
= 12mA
7.0
V
Supply Rise Time
SHUTDOWN to Turn-On
0.2
ms
Consult factory for Military Grade parts.
3
LTC1349
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Slew Rate
R
L
= 3k, C
L
= 51pF
8
30
V/
s
R
L
= 3k, C
L
= 2500pF
3
5
V/
s
Driver Propagation Delay
t
HLD
(Figure 1)
q
2
3.5
s
(TTL to RS232)
t
LHD
(Figure 1)
q
2
3.5
s
Receiver Propagation Delay
t
HLR
(Figure 2)
q
0.3
0.8
s
(RS232 to TTL)
t
LHR
(Figure 2)
q
0.2
0.8
s
ELECTRICAL C
C
HARA TERISTICS
C
D
V
CC
= 5V, C1 = C2 = C3 = C4 = 0.1
F, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Power Supply
V
CC
Supply Current
No Load (All Drivers V
IN
= V
CC
)(Note 2), 0
T
A
70
C
q
0.3
0.8
mA
No Load (All Drivers V
IN
= 0V)(Note 2), 0
T
A
70
C
q
0.5
1.0
mA
No Load (All Drivers V
IN
= V
CC
)(Note 2), 40
C
T
A
85
C
q
0.3
1.0
mA
No Load (All Drivers V
IN
= 0V)(Note 2), 40
C
T
A
85
C
q
0.5
1.5
mA
Supply Leakage Current (V
CC
)
SHUTDOWN (Note 3)
q
35
50
A
On/Off Threshold Low
q
1.4
0.8
V
On/Off Threshold High
q
2.0
1.4
V
C
C
HARA TERISTICS
AC
V
CC
= 5V, C1 = C2 = C3 = C4 = 0.1
F, unless otherwise noted.
TYPICAL PERFOR A CE CHARACTERISTICS
W U
TEMPERATURE (C)
40
8
DRIVER OUTPUT VOLTAGE (V)
6
2
0
2
40
10
LTC1349 TPC01
4
0
100
4
6
8
20
20
60
80
R
L
= 3k
OUTPUT HIGH
V
CC
= 5V
V
CC
= 4.5V
OUTPUT LOW
V
CC
= 4.5V
V
CC
= 5V
Driver Output Voltage
DATA RATE (k BAUD)
0
SUPPLY CURRENT (mA)
150
45
40
35
30
25
20
15
10
5
0
LTC1349 TPC03
50
175
25
75
100
125
V
CC
= 5V
R
L
= 3k
C
L
= 2500pF
3 DRIVERS ACTIVE
Supply Current vs Data Rate
TEMPERATURE (C)
40
THRESHOLD VOLTAGE (V)
1.8
2.0
2.2
20
60
LTC1349 TPC02
1.6
1.4
20
0
40
80
100
1.2
1.0
V
TH
V
TL
Receiver Input Thresholds
The
q
denotes specifications which apply over the operating temperature
range (0
C
T
A
70
Cfor commercial grade, 40
C
T
A
85
C for
industrial grade).
Note 1: Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
Note 2: Supply current is measured with driver and receiver outputs
unloaded.
Note 3: Supply current and leakage current measurements in SHUTDOWN
are performed with V
ON/OFF
= 0V.
4
LTC1349
V
CC
: 5V Input Supply Pin. Supply current is typically 35
A
in the SHUTDOWN mode. This pin should be decoupled
with a 0.1
F ceramic capacitor.
GND: Ground Pin.
ON/OFF: TTL/CMOS Compatible SHUTDOWN Pin. A logic
low puts the device in SHUTDOWN mode, with receivers
4 and 5 kept alive and the supply current equal to 35
A. All
driver outputs and other receiver outputs are in high
impedance state. This pin can not float.
V
+
: Positive Supply Output (RS232 Drivers). V
+
2V
CC
1V. This pin requires an external capacitor C = 0.1
F for
charge storage. The capacitor may be tied to ground or 5V.
TYPICAL PERFOR A CE CHARACTERISTICS
W U
V
CC
Supply Current
Driver Short-Circuit Current
Driver Leakage in SHUTDOWN
TEMPERATURE (C)
0
SUPPLY CURRENT (mA)
60
20
16
14
12
10
8
6
4
2
0
LTC1349 TPC04
20
70
10
30
40
50
3 DRIVERS LOADED
R
L
= 3k
1 DRIVER LOADED
R
L
= 3k
TEMPERATURE (C)
0
LEAKAGE CURRENT (
A)
60
45
40
35
30
25
20
15
10
5
0
LTC1349 TPC05
20
70
10
30
40
50
V
OUT
= 20V
V
OUT
= 20V
TEMPERATURE (C)
40
0
SHORT-CIRCUIT CURRENT (mA)
4
8
10
12
40
20
LTC1349 TPC06
6
0
80
14
16
18
20
60
20
100
I
SC
+
I
SC
Receiver Short-Circuit Current
Receiver Output Waveforms
Driver Output Waveforms
TEMPERATURE (C)
40
10
SHORT-CIRCUIT CURRENT (mA)
30
60
0
40
60
LTC1349 TPC07
20
50
40
20
20
80
100
I
SC
I
SC
+
DRIVER
OUTPUT
R
L
= 3k
DRIVER
OUTPUT
R
L
= 3k
C
L
= 2500pF
INPUT
RECEIVER
OUTPUT
C
L
= 2500pF
INPUT
LTC1349 TPC08
LTC1349 TPC09
PI FU CTIO S
U
U
U
With multiple devices, the V
+
and V
pins may be paral-
leled into common capacitors. For large numbers of de-
vices, increasing the size of the shared common storage
capacitors is recommended to reduce ripple.
V
: Negative Supply Output (RS232 Drivers). V
2V
CC
1.5V. This pin requires an external capacitor C = 0.1
F for
charge storage.
C1
+
, C1
, C2
+
, C2
: Commutating Capacitor Inputs. These
pins require two external capacitors C = 0.1
F: one from
C1
+
to C1
, and another from C2
+
to C2
. To maintain
charge pump efficiency, the capacitor's effective series
resistance should be less than 20
.
5
LTC1349
PI FU CTIO S
U
U
U
DRIVER IN: RS232 Driver Input Pins. Inputs are TTL/
CMOS compatible. Inputs should not be allowed to float.
Tie unused inputs to V
CC
.
DRIVER OUT: Driver Outputs at RS232 Voltage Levels.
Outputs are in a high impedance state when in SHUT-
DOWN mode or V
CC
= 0V. The driver outputs are protected
against ESD to
10kV for human body model discharges.
RX IN: Receiver Inputs. These pins can be forced to
25V
without damage. The receiver inputs are protected against
ESD to
10kV for human body model discharges. Each
receiver provides 0.4V of hysteresis for noise immunity.
RX OUT: Receiver Outputs with TTL/CMOS Voltage Lev-
els. Receiver 1, 2 and 3 outputs are in a high impedance
state when in SHUTDOWN mode to allow data line sharing.
Receivers 4 and 5 are kept alive in SHUTDOWN.
TI
W
E WAVEFOR
S
U
G
WITCHI
W
S
Figure 1. Driver Propagation Delay Timing
Figure 2. Receiver Propagation Delay Timing
1.4V
0V
V
CC
0V
V
+
V
0V
DRIVER
INPUT
DRIVER
OUTPUT
1.4V
t
HLD
t
LHD
LTC1349 F01
0.8V
V
CC
0V
2.4V
RX
INPUT
RX
OUTPUT
1.3V
t
HLR
1.7V
t
LHR
LTC1349 F02
V
CC
0V
TEST CIRCUITS
Driver Timing Test Load
Receiver Timing Test Load
DRIVER
DRIVER
INPUT
3k
51pF
DRIVER
OUTPUT
LTC1349 TA03
RX
RX INPUT
51pF
RX
OUTPUT
LTC1349 TA04
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