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1
LTC1348
3.3V/5V Low Power RS232
3-Driver/5-Receiver Transceiver
S
FEATURE
D
U
ESCRIPTIO
s
Low Supply Current: 600
A at 3.3V
s
Supply Current in Shutdown: 0.2
A
s
Supply Current in Receiver Alive Mode: 15
A
s
ESD Protection over
10kV
s
Operates from a Single 3V to 5.5V Supply
s
Operates to 120kBaud with 0.1
F Flying Capacitors
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
Flowthrough Architecture
The LTC
1348 is a 3-driver/5-receiver RS232 transceiver
with very low supply current. The charge pump only
requires five 0.1
F capacitors. The LTC1348 provides full
RS232 output levels when operated over a wide supply
range of 3V to 5.5V
The transceiver operates in one of four modes: Normal,
Receiver Disable, Receiver Alive and Shutdown. In Normal
or Receiver Disable mode, I
CC
is only 600
A at 3.3V and
800
A at 5V in the no load condition. In Shutdown mode,
the supply current is further reduced to 0.2
A. In Receiver
Alive mode, all five receivers are kept alive and the supply
current is 15
A. All RS232 outputs assume a high imped-
ance state in Shutdown or Receiver Alive mode or with the
power off. The receiver outputs assume a high impedance
state in Receiver Disable or with the power off.
The LTC1348 is fully compliant with all data rate and
overvoltage RS232 specifications. The transceiver oper-
ates up to 120kbaud with all drivers loaded with 1000pF,
3k
. 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
s
Printers
s
Portable Instruments
LT1348 TA01
C5
0.1
F
C2
0.1
F
C3
0.1
F
C4
0.1
F
LTC1348
1
2
3
4
5
6
7
8
9
10
11
12
13
14
DR 1 OUT
RX1 IN
DR 2 OUT
RX2 IN
RX3 IN
RX4 IN
DR 3 OUT
RX5 IN
28
27
26
25
24
23
22
21
20
19
18
17
16
15
DR 1 IN
RX1 OUT
DR 2 IN
RX2 OUT
RX3 OUT
RX4 OUT
DR 3 IN
RX5 OUT
DREN
RXEN
V
V
+
V
CC
GND
C1
0.1
F
3-Drivers/5-Receivers with Shutdown
U
A
O
PPLICATI
TYPICAL
Supply Current
, LTC and LT are registered trademarks of Linear Technology Corporation.
TEMPERATURE (C)
40
SUPPLY CURRENT (mA)
1.4
20
LT1348 TA02
0.8
0.4
20
0
40
0.2
0
1.6
1.2
1.0
0.6
SHUTDOWN CURRENT (
A)
1.4
0.8
0.4
0.2
0
1.6
1.2
1.0
0.6
60
80
QUIESCENT
CURRENT
SHUTDOWN
CURRENT
V
CC
= 5V
V
CC
= 3.3V
V
CC
= 3.3V
OR 5V
2
LTC1348
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
LTC1348CG
LTC1348CSW
LTC1348IG
LTC1348ISW
(Note 1)
Supply Voltage (V
CC
) ................................................ 6V
Input Voltage
Driver ....................................... 0.3V to V
CC
+ 0.3V
Receiver ............................................... 25V to 25V
Driver/Receiver Enable 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
LTC1348C................................................ 0
C to 70
C
LTC1348I ............................................ 40
C to 85
C
Storage Temperature Range ................ 65
C to 150
C
Lead Temperature (Soldering, 10 sec)................. 300
C
Consult factory for Military grade parts.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
V
+
C2
+
C2
V
CC
C1
+
C1
DR1 OUT
RX1 IN
DR2 OUT
RX2 IN
RX3 IN
RX4 IN
DR3 OUT
RX5 IN
28
27
26
25
24
23
22
21
20
19
18
17
16
15
V
C3
+
C3
DR1 IN
RX1 OUT
DR2 IN
RX2 OUT
RX3 OUT
RX4 OUT
DR3 IN
RX5 OUT
DREN
RXEN
GND
TOP VIEW
SW PACKAGE
28-LEAD PLASTIC SO
G PACKAGE
28-LEAD PLASTIC SSOP
T
JMAX
= 125
C,
JA
= 96
C/W (G)
T
JMAX
= 125
C,
JA
= 85
C/W (SW)
ELECTRICAL C
C
HARA TERISTICS
C
D
V
CC
= 3V to 5.5V, C1 to C4 = 0.1
F, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Any Driver
Output Voltage Swing
V
CC
= 3.3V, 3k to GND
Positive
q
5.0
6.2
V
Negative
q
5.0
6.0
V
Logic Input Voltage Level
Input Low Level (V
OUT
= High)
q
0.8
V
Input High Level (V
OUT
= Low), V
CC
= 3.3V
q
2.0
V
Input High Level (V
OUT
= Low), V
CC
= 5V
q
2.4
V
Logic Input Current
V
IN
= V
CC
q
5
A
V
IN
= 0V
q
5
35
A
Output Short-Circuit Current
V
OUT
= 0V
12
mA
Output Leakage Current
Shutdown (Note 3) or Receiver Alive Mode (Note 4),
q
10
500
A
V
OUT
=
20V
Any Receiver
Input Voltage Thresholds
Input Threshold (Receiver Alive Mode)
0.8
1.5
2.4
V
Input Low Threshold (Normal Mode)
0.8
1.3
V
Input High Threshold (Normal Mode)
1.7
2.4
V
Hysteresis
Normal Mode
0.3
V
Input Resistance
V
IN
=
10V
3
5
7
k
Output Voltage
Output Low, I
OUT
= 1.6mA
q
0.2
0.4
V
Output High, I
OUT
= 160
A
q
V
CC
0.6V
V
Output Short-Circuit Current
Sinking Current, V
OUT
= V
CC
3
20
mA
Output Leakage Current
Shutdown (Note 3), 0V
V
OUT
V
CC
q
1
10
A
3
LTC1348
ELECTRICAL C
C
HARA TERISTICS
C
D
V
CC
= 3V to 5.5V, C1 to C4 = 0.1
F, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Power Supply Generator
V
+
Output Voltage
I
OUT
= 0mA
8.0
V
I
OUT
= 8mA
7.5
V
V
Output Voltage
I
OUT
= 0mA
8.0
V
I
OUT
= 8mA
7.0
V
Supply Rise Time
Shutdown to Turn-On
0.2
ms
Power Supply
V
CC
Supply Current
No Load (Note 2) V
CC
= 3.3V
q
0.6
2.0
mA
No Load (Note 2) V
CC
= 5V
q
0.8
2.5
mA
Receiver Alive Mode (Note 4) V
CC
= 3.3V or 5V
q
15
30
A
Supply Leakage Current (V
CC
)
Shutdown (Note 3)
q
0.2
10
A
Driver/Receiver Enable Threshold Low
q
0.8
V
Driver/Receiver Enable Threshold High
V
CC
= 3.3V
q
2.0
V
Driver/Receiver Enable Threshold High
V
CC
= 5V
q
2.4
V
AC ELECTRICAL CHARACTERISTICS
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Maximum Data Rate
R
L
= 3k, C
L
= 1000pF, One Driver Switching
120
250
kbps
Slew Rate
V
CC
= 5V, R
L
= 3k, C
L
= 51pF
8
30
V/
s
V
CC
= 3.3V, R
L
= 3k, C
L
= 2500pF
3
V/
s
Driver Propagation Delay
t
HLD
(Figure 1)
q
2.5
4
s
(TTL to RS232)
t
LHD
(Figure 1)
q
2.5
4
s
Receiver Propagation Delay
t
HLR
(Figure 2) (Normal Mode)
q
0.3
1
s
(RS232 to TTL)
t
LHR
(Figure 2) (Normal Mode)
q
0.2
1
s
t
HLR
(Figure 2) (Receiver Alive Mode)
q
1.0
4
s
t
LHR
(Figure 2) (Receiver Alive Mode)
q
0.2
4
s
Note 3: Supply current measurement in Shutdown is performed with
V
DREN
and V
RXEN
= 0V.
Note 4: Supply current measurement in Receiver Alive mode is performed
with V
DREN
= 0V and V
RXEN
= V
CC
.
V
CC
= 3V to 5.5V, C1 to C4 = 0.1
F, unless otherwise noted.
The
q
denotes specifications which apply over the full operating
temperature range (0
C
T
A
70
C for Commercial grade and
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. The V
DREN
and V
RXEN
= V
CC
.
4
LTC1348
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
Driver Output Voltage High/Low
vs Load Capacitance (C
L
)
Supply Current
vs Driver Data Rate
Driver Output Voltage High/Low
vs Load Capacitance (C
L
)
Driver Output Voltage High/Low
vs Temperature (
C)
TEMPERATURE (
C)
0
0
LEAKAGE CURRENT (
A)
5
15
20
25
50
45
LTC1348 G06
10
20
10
30
40
60
70
30
35
40
V
OUT
= 20V
V
OUT
= 20V
V
CC
= 3.3V
LOAD CAPACITANCE (pF)
0
7
DRIVER OUTPUT VOLTAGE HIGH/LOW
5
3
1
7
6
4
2
0
2
4
6
3
1000
2000
5000
5
1
3000
4000
250kbps
250kbps
120kbps
120kbps
64kbps
64kbps 20kbps
20kbps
V
CC
= 3.3V
0.1
F FLYING CAPACITORS
ALL DRIVERS LOADED 3k
+ C
L
1 DRIVER DRIVEN
LTC1348 G01
OUTPUT HIGH
OUTPUT LOW
LOAD CAPACITANCE (pF)
0
7
DRIVER OUTPUT VOLTAGE HIGH/LOW
5
3
1
7
6
4
2
0
2
4
6
3
1000
2000
5000
5
1
3000
4000
120kbps
120kbps
64kbps
64kbps
20kbps
V
CC
= 3.3V
0.1
F FLYING CAPACITORS
ALL DRIVERS DRIVEN AND
LOADED 3k
+ C
L
LTC1348 G02
OUTPUT HIGH
OUTPUT LOW
20kbps
Driver Leakage in SHUTDOWN
vs Temperature (
C)
TEMPERATURE (
C)
0
7
DRIVER OUTPUT VOLTAGE HIGH/LOW
5
3
1
7
6
4
2
0
2
4
6
3
10
20
30
70
5
1
40
50
60
LTC1348 G04
V
CC
= 3V
V
CC
= 3V
V
CC
= 3.3V
OUTPUT HIGH
OUTPUT LOW
V
CC
= 3.3V
ALL DRIVERS
LOADED WITH 3k
Driver Short-Circuit Current
vs Temperature (
C)
With V
CC
= 3.3V
All Driver Outputs Loaded with
3k
, 1000pF. 1 Driven at 250kbps
DRIVER DATA RATE
0
SUPPLY CURRENT (mA)
30
40
50
200
LTC1348 G03
20
10
0
50
100
150
250
3 OUTPUT LOADED
3k
// 2500pF
1 OUTPUT LOADED
3k
// 2500pF
V
CC
= 3.3V
TEMPERATURE (
C)
40
0
SHORT-CIRCUIT CURRENT (mA)
4
8
10
12
60
20
LTC1348 G05
6
0
20
20
40
80
100
14
16
18
I
SC
I
SC
+
V
CC
= 3.3V
LTC1348 G07
DRIVER
INPUT
DRIVEN DRIVER
OUTPUT
5
LTC1348
PI FU CTIO S
U
U
U
V
CC
: 3V to 5.5V Input Supply Pin. This pin should be
decoupled with a 0.1
F ceramic capacitor.
GND: Ground Pin.
RXEN: TTL/CMOS Compatible Enable Pin. Refer to Table
1 for its functional description.
DREN: TTL/CMOS Compatible Enable Pin. Refer to Table
1 for its functional description.
V
+
: Positive Supply Output (RS232 Drivers). This pin
requires an external capacitor C = 0.1
F for charge stor-
age. The capacitor may be tied to ground or V
CC
. With
multiple devices, the V
+
and V
pins may be paralleled into
common capacitors. For large numbers of devices, in-
creasing the size of the shared common storage capaci-
tors is recommended to reduce ripple.
V
: Negative Supply Output (RS232 Drivers). This pin
requires an external capacitor C = 0.1
F for charge
storage.
C1
+
, C1
, C2
+
, C2
, C3
+
, C3
: Commutating Capacitor
Inputs. These pins require three external capacitors C =
0.1
F: one from C1
+
to C1
, another from C2
+
to C2
and
another from C3
+
to C3
. To maintain charge pump
efficiency, the capacitor's effective series resistance should
be less than 1
. Ceramic capacitors are recommended.
DR IN: RS232 Driver Input Pins. Inputs are TTL/CMOS
compatible. The inputs of unused drivers can be left
unconnected since 300k input pull-up resistors to V
CC
are
included on chip. To minimize power consumption, the
internal driver pull-up resistors are disconnected from V
CC
in the Shutdown or Receiver Alive mode.
DR OUT: Driver Outputs at RS232 Voltage Levels. Outputs
are in a high impedance state when in the Shutdown,
Receiver Alive 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. In
Receiver Alive mode all receivers have no hysteresis.
RX OUT: Receiver Outputs with TTL/CMOS Voltage Lev-
els. Outputs are in a high impedance state when in the
Shutdown or Receiver Disable mode to allow data line
sharing.
Table 1. Functional Description
MODE
RX ENABLE
DR ENABLE
DRIVERS
RECEIVERS
I
CC
TYP
Shutdown
0
0
All Drivers Shutdown.
All Receivers Shutdown.
0.2
A
All Driver Outputs Assume High Impedance.
All Receiver Outputs Assume High Impedance.
All Driver Pull-Up Resistors Disconnect
From V
CC
.
Receiver
0
1
All Drivers Alive.
All Receiver Outputs in Three-State.
600
A at
Disable
3.3V,
800
A at
5V
Receiver
1
0
All Drivers Shutdown.
All Receivers Alive.
15
A
Alive
All Driver Outputs in Three-State.
All Driver Pull-Up Resistors Disconnect
From V
CC
.
Normal
1
1
All Drivers Alive.
All Receivers Alive.
600
A at
3.3V,
800
A at
5V
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