LTC1348
3.3V/5V Low Power RS232
3-Driver/5-Receiver Transceiver
FEATURES
s
s
s
s
s
s
s
s
DESCRIPTIO
s
s
Low Supply Current: 600µA at 3.3V
Supply Current in Shutdown: 0.2µA
Supply Current in Receiver Alive Mode: 15µA
ESD Protection over
±10kV
Operates from a Single 3V to 5.5V Supply
Operates to 120kBaud with 0.1µF Flying Capacitors
Three-State Outputs Are High Impedance When Off
Output Overvoltage Does Not Force Current
Back into Supplies
RS232 I/O Lines Can Be Forced to
±25V
Without Damage
Flowthrough Architecture
The LTC
®
1348 is a 3-driver/5-receiver RS232 transceiver
with very low supply current. The charge pump only
requires five 0.1µF 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 600µA at 3.3V and
800µA at 5V in the no load condition. In Shutdown mode,
the supply current is further reduced to 0.2µA. In Receiver
Alive mode, all five receivers are kept alive and the supply
current is 15µA. 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,
3kΩ. Both driver outputs and receiver inputs can be forced
to
±25V
without damage and can survive multiple
±10kV
ESD strikes.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATI
s
s
s
s
S
Notebook Computers
Palmtop Computers
Printers
Portable Instruments
TYPICAL APPLICATI
V
+
C5
0.1µF
C2
0.1µF
V
CC
C1
0.1µF
DR 1 OUT
RX1 IN
DR 2 OUT
RX2 IN
RX3 IN
RX4 IN
DR 3 OUT
RX5 IN
1
2
3
4
5
6
7
8
9
10
11
12
13
14
LTC1348
3-Drivers/5-Receivers with Shutdown
28
27
26
25
24
23
22
21
20
19
18
17
16
15
C3
0.1µF
DR 1 IN
RX1 OUT
DR 2 IN
RX2 OUT
RX3 OUT
RX4 OUT
DR 3 IN
RX5 OUT
DREN
RXEN
GND
LT1348 • TA01
V
–
C4
0.1µF
SUPPLY CURRENT (mA)
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
–40
–20
V
CC
= 5V
V
CC
= 3.3V
V
CC
= 3.3V
OR 5V
SHUTDOWN
CURRENT
QUIESCENT
CURRENT
U
Supply Current
1.6
1.4
SHUTDOWN CURRENT (µA)
UO
UO
1.2
1.0
0.8
0.6
0.4
0.2
0
40
20
TEMPERATURE (˚C)
0
60
80
LT1348 •TA02
1
LTC1348
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
V
+
1
C2
+
2
C2
–
3
V
CC
4
C1
+
5
C1
–
6
DR1 OUT 7
RX1 IN 8
DR2 OUT 9
RX2 IN 10
RX3 IN 11
RX4 IN 12
DR3 OUT 13
RX5 IN 14
G PACKAGE
28-LEAD PLASTIC SSOP
28 V
–
27 C3
+
26 C3
–
25 DR1 IN
24 RX1 OUT
23 DR2 IN
22 RX2 OUT
21 RX3 OUT
20 RX4 OUT
19 DR3 IN
18 RX5 OUT
17 DREN
16 RXEN
15 GND
SW PACKAGE
28-LEAD PLASTIC SO
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
ORDER PART
NUMBER
LTC1348CG
LTC1348CSW
LTC1348IG
LTC1348ISW
T
JMAX
= 125°C,
θ
JA
= 96°C/W (G)
T
JMAX
= 125°C,
θ
JA
= 85°C/W (SW)
Consult factory for Military grade parts.
DC ELECTRICAL CHARACTERISTICS
V
CC
= 3V to 5.5V, C1 to C4 = 0.1µF, unless otherwise noted.
PARAMETER
Any Driver
Output Voltage Swing
Logic Input Voltage Level
CONDITIONS
V
CC
= 3.3V, 3k to GND
Positive
Negative
q
q
q
q
q
q
q
q
MIN
5.0
– 5.0
2.0
2.4
TYP
6.2
– 6.0
MAX
UNITS
V
V
V
V
V
µA
µA
mA
µA
Logic Input Current
Output Short-Circuit Current
Output Leakage Current
Any Receiver
Input Voltage Thresholds
Input Low Level (V
OUT
= High)
Input High Level (V
OUT
= Low), V
CC
= 3.3V
Input High Level (V
OUT
= Low), V
CC
= 5V
V
IN
= V
CC
V
IN
= 0V
V
OUT
= 0V
Shutdown (Note 3) or Receiver Alive Mode (Note 4),
V
OUT
=
±20V
Input Threshold (Receiver Alive Mode)
Input Low Threshold (Normal Mode)
Input High Threshold (Normal Mode)
Normal Mode
V
IN
=
±10V
Output Low, I
OUT
= – 1.6mA
Output High, I
OUT
= 160µA
Sinking Current, V
OUT
= V
CC
Shutdown (Note 3), 0V
≤
V
OUT
≤
V
CC
0.8
–5
±12
±10
5
– 35
±500
0.8
0.8
Hysteresis
Input Resistance
Output Voltage
Output Short-Circuit Current
Output Leakage Current
3
q
q
q
1.5
1.3
1.7
0.3
5
0.2
– 20
1
2.4
2.4
7
0.4
V
CC
– 0.6V
–3
10
2
U
V
V
V
V
kΩ
V
V
mA
µA
W
U
U
W W
W
LTC1348
DC ELECTRICAL CHARACTERISTICS
V
CC
= 3V to 5.5V, C1 to C4 = 0.1µF, unless otherwise noted.
PARAMETER
Power Supply Generator
V
+
Output Voltage
V
–
Output Voltage
Supply Rise Time
Power Supply
V
CC
Supply Current
CONDITIONS
I
OUT
= 0mA
I
OUT
= 8mA
I
OUT
= 0mA
I
OUT
= – 8mA
Shutdown to Turn-On
No Load (Note 2) V
CC
= 3.3V
No Load (Note 2) V
CC
= 5V
Receiver Alive Mode (Note 4) V
CC
= 3.3V or 5V
Shutdown (Note 3)
V
CC
= 3.3V
V
CC
= 5V
q
q
q
q
q
q
q
MIN
TYP
8.0
7.5
– 8.0
– 7.0
0.2
0.6
0.8
15
0.2
MAX
UNITS
V
V
V
V
ms
Supply Leakage Current (V
CC
)
Driver/Receiver Enable Threshold Low
Driver/Receiver Enable Threshold High
Driver/Receiver Enable Threshold High
2.0
2.5
30
10
0.8
2.0
2.4
mA
mA
µA
µA
V
V
V
AC ELECTRICAL CHARACTERISTICS
V
CC
= 3V to 5.5V, C1 to C4 = 0.1µF, unless otherwise noted.
PARAMETER
Maximum Data Rate
Slew Rate
Driver Propagation Delay
(TTL to RS232)
Receiver Propagation Delay
(RS232 to TTL)
CONDITIONS
R
L
= 3k, C
L
= 1000pF, One Driver Switching
V
CC
= 5V, R
L
= 3k, C
L
= 51pF
V
CC
= 3.3V, R
L
= 3k, C
L
= 2500pF
t
HLD
(Figure 1)
t
LHD
(Figure 1)
t
HLR
(Figure 2) (Normal Mode)
t
LHR
(Figure 2) (Normal Mode)
t
HLR
(Figure 2) (Receiver Alive Mode)
t
LHR
(Figure 2) (Receiver Alive Mode)
MIN
120
3
q
q
q
q
q
q
TYP
250
8
2.5
2.5
0.3
0.2
1.0
0.2
MAX
30
4
4
1
1
4
4
UNITS
kbps
V/µs
V/µs
µs
µs
µs
µs
µs
µs
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
.
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
.
3
LTC1348
TYPICAL PERFORMANCE CHARACTERISTICS
Driver Output Voltage High/Low
vs Load Capacitance (C
L
)
7
6
5
4
3
2
1
0
–1
–2
–3
–4
–5
–6
–7
0
DRIVER OUTPUT VOLTAGE HIGH/LOW
250kbps
120kbps
64kbps
OUTPUT HIGH
V
CC
= 3.3V
0.1µF FLYING CAPACITORS
ALL DRIVERS LOADED 3kΩ + C
L
1 DRIVER DRIVEN
OUTPUT LOW
64kbps 20kbps
250kbps
120kbps
20kbps
DRIVER OUTPUT VOLTAGE HIGH/LOW
SUPPLY CURRENT (mA)
3000
4000
1000
2000
LOAD CAPACITANCE (pF)
Driver Output Voltage High/Low
vs Temperature (°C)
7
6
5
4
3
2
1
0
–1
–2
–3
–4
–5
–6
–7
0
20
DRIVER OUTPUT VOLTAGE HIGH/LOW
V
CC
= 3.3V
OUTPUT HIGH
SHORT-CIRCUIT CURRENT (mA)
LEAKAGE CURRENT (µA)
ALL DRIVERS
LOADED WITH 3kΩ
OUTPUT LOW
V
CC
= 3.3V
V
CC
= 3V
10
40
50
20
30
TEMPERATURE (°C)
4
U W
V
CC
= 3V
60
70
Driver Output Voltage High/Low
vs Load Capacitance (C
L
)
7
6
5
4
3
2
1
0
–1
–2
–3
–4
–5
–6
–7
0
50
Supply Current
vs Driver Data Rate
3 OUTPUT LOADED
3kΩ // 2500pF
40
120kbps
64kbps
OUTPUT HIGH
20kbps
V
CC
= 3.3V
0.1µF FLYING CAPACITORS
ALL DRIVERS DRIVEN AND
LOADED 3kΩ + C
L
OUTPUT LOW
120kbps
64kbps
20kbps
3000
4000
1000
2000
LOAD CAPACITANCE (pF)
5000
LTC1348 G02
30
1 OUTPUT LOADED
3kΩ // 2500pF
20
10
V
CC
= 3.3V
0
50
150
200
100
DRIVER DATA RATE
250
0
5000
LTC1348 G01
LTC1348 G03
Driver Short-Circuit Current
vs Temperature (°C)
45
V
CC
= 3.3V
40
35
30
25
20
15
10
5
0
–20
0
20
40
60
TEMPERATURE (°C)
80
100
18
16
14
12
10
8
6
4
0
–40
I
SC
+
Driver Leakage in SHUTDOWN
vs Temperature (°C)
V
CC
= 3.3V
I
SC–
V
OUT
= –20V
V
OUT
= 20V
0
10
20
30
40
50
TEMPERATURE (°C)
60
70
LTC1348 G04
LTC1348 G05
LTC1348 G06
With V
CC
= 3.3V
All Driver Outputs Loaded with
3kΩ, 1000pF. 1 Driven at 250kbps
DRIVEN DRIVER
OUTPUT
DRIVER
INPUT
LTC1348 G07
LTC1348
PI FU CTIO S
V
CC
:
3V to 5.5V Input Supply Pin. This pin should be
decoupled with a 0.1µF 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 = 0.1µF 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 = 0.1µF for charge
storage.
C1
+
, C1
–
, C2
+
, C2
–
, C3
+
, C3
–
:
Commutating Capacitor
Inputs. These pins require three external capacitors C =
0.1µF: one from C1
+
to C1
–
, another from C2
+
to C2
–
and
another from C3
+
to C3
–
. To maintain charge pump
Table 1. Functional Description
MODE
Shutdown
RX ENABLE
0
DR ENABLE
0
DRIVERS
All Drivers Shutdown.
All Driver Outputs Assume High Impedance.
All Driver Pull-Up Resistors Disconnect
From V
CC
.
All Drivers Alive.
RECEIVERS
All Receivers Shutdown.
All Receiver Outputs Assume High Impedance.
I
CC
TYP
0.2µA
Receiver
Disable
0
Receiver
Alive
1
Normal
1
U
U
U
efficiency, the capacitor’s effective series resistance should
be less than 1Ω. 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.
1
All Receiver Outputs in Three-State.
600µA at
3.3V,
800µA at
5V
15µA
0
All Drivers Shutdown.
All Driver Outputs in Three-State.
All Driver Pull-Up Resistors Disconnect
From V
CC
.
All Drivers Alive.
All Receivers Alive.
1
All Receivers Alive.
600µA at
3.3V,
800µA at
5V
5
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