LTC1348
3.3V/5V Low Power RS232
3-Driver/5-Receiver Transceiver
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DESCRIPTIO
FEATURES
■
■
■
■
■
■
■
■
■
■
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
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APPLICATI
■
■
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S
Notebook Computers
Palmtop Computers
Printers
Portable Instruments
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, ICC 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 impedance 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 operates 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.
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TYPICAL APPLICATI
Supply Current
3-Drivers/5-Receivers with Shutdown
2
VCC
C1
0.1µF
DR 1 OUT
RX1 IN
DR 2 OUT
RX2 IN
RX3 IN
RX4 IN
DR 3 OUT
RX5 IN
LTC1348
V–
27
3
26
4
25
5
24
6
23
7
22
8
21
9
20
10
19
11
18
12
17
13
16
14
15
C3
0.1µF
DR 1 IN
RX1 OUT
DR 2 IN
RX2 OUT
RX3 OUT
C4
0.1µF
1.6
1.6
1.4
1.4
1.2
1.0
RX5 OUT
DREN
0.8
RXEN
0.8
VCC = 3.3V
0.6
0.4
VCC = 3.3V
OR 5V
0.2
0
–40
1.0
VCC = 5V
RX4 OUT
DR 3 IN
1.2
QUIESCENT
CURRENT
0.6
SHUTDOWN
CURRENT
0.4
SHUTDOWN CURRENT (µA)
C2
0.1µF
28
1
SUPPLY CURRENT (mA)
V+
C5
0.1µF
0.2
0
–20
0
40
20
TEMPERATURE (˚C)
60
80
LT1348 •TA02
GND
LT1348 • TA01
1
LTC1348
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RATI GS
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AXI U
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ABSOLUTE
PACKAGE/ORDER I FOR ATIO
(Note 1)
Supply Voltage (VCC) ................................................ 6V
Input Voltage
Driver ....................................... – 0.3V to V CC + 0.3V
Receiver ............................................... – 25V to 25V
Driver/Receiver Enable Pin ........ – 0.3V to VCC + 0.3V
Output Voltage
Driver ................................................... – 25V to 25V
Receiver .................................... – 0.3V to VCC + 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
TOP VIEW
V+
1
28
V–
C2 + 2
27 C3+
C2 –
26 C3 –
3
VCC 4
25 DR1 IN
C1 + 5
24 RX1 OUT
C1 – 6
23 DR2 IN
DR1 OUT 7
22 RX2 OUT
RX1 IN 8
21 RX3 OUT
DR2 OUT 9
20 RX4 OUT
RX2 IN 10
19 DR3 IN
RX3 IN 11
18 RX5 OUT
RX4 IN 12
17 DREN
DR3 OUT 13
16 RXEN
RX5 IN 14
LTC1348CG
LTC1348CSW
LTC1348IG
LTC1348ISW
15 GND
G PACKAGE
28-LEAD PLASTIC SSOP
SW PACKAGE
28-LEAD PLASTIC SO
TJMAX = 125°C, θJA = 96°C/W (G)
TJMAX = 125°C, θJA = 85°C/W (SW)
Consult factory for Military grade parts.
DC ELECTRICAL CHARACTERISTICS
VCC = 3V to 5.5V, C1 to C4 = 0.1µF, unless otherwise noted.
PARAMETER
CONDITIONS
Any Driver
Output Voltage Swing
VCC = 3.3V, 3k to GND
Logic Input Voltage Level
Logic Input Current
Output Short-Circuit Current
Output Leakage Current
Any Receiver
Input Voltage Thresholds
Hysteresis
Input Resistance
Output Voltage
Output Short-Circuit Current
Output Leakage Current
2
Positive
Negative
Input Low Level (VOUT = High)
Input High Level (VOUT = Low), VCC = 3.3V
Input High Level (VOUT = Low), VCC = 5V
VIN = VCC
VIN = 0V
VOUT = 0V
Shutdown (Note 3) or Receiver Alive Mode (Note 4),
VOUT = ±20V
Input Threshold (Receiver Alive Mode)
Input Low Threshold (Normal Mode)
Input High Threshold (Normal Mode)
Normal Mode
VIN = ±10V
Output Low, IOUT = – 1.6mA
Output High, IOUT = 160µA
Sinking Current, VOUT = VCC
Shutdown (Note 3), 0V ≤ VOUT ≤ VCC
MIN
TYP
●
●
5.0
– 5.0
6.2
– 6.0
●
●
●
2.0
2.4
0.8
●
●
–5
±12
±10
●
0.8
0.8
3
●
●
●
MAX
VCC – 0.6V
–3
1.5
1.3
1.7
0.3
5
0.2
– 20
1
5
– 35
±500
2.4
2.4
7
0.4
10
UNITS
V
V
V
V
V
µA
µA
mA
µA
V
V
V
V
kΩ
V
V
mA
µA
LTC1348
DC ELECTRICAL CHARACTERISTICS
VCC = 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
VCC Supply Current
Supply Leakage Current (VCC)
Driver/Receiver Enable Threshold Low
Driver/Receiver Enable Threshold High
Driver/Receiver Enable Threshold High
CONDITIONS
MIN
IOUT = 0mA
IOUT = 8mA
IOUT = 0mA
IOUT = – 8mA
Shutdown to Turn-On
TYP
MAX
8.0
7.5
– 8.0
– 7.0
0.2
No Load (Note 2) VCC = 3.3V
No Load (Note 2) VCC = 5V
Receiver Alive Mode (Note 4) VCC = 3.3V or 5V
Shutdown (Note 3)
●
●
●
●
●
●
V
V
V
V
ms
0.6
0.8
15
0.2
2.0
2.5
30
10
0.8
TYP
250
8
MAX
2.5
2.5
0.3
0.2
1.0
0.2
4
4
1
1
4
4
●
VCC = 3.3V
VCC = 5V
UNITS
2.0
2.4
mA
mA
µA
µA
V
V
V
AC ELECTRICAL CHARACTERISTICS
VCC = 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
RL = 3k, CL = 1000pF, One Driver Switching
VCC = 5V, RL = 3k, CL = 51pF
VCC = 3.3V, RL = 3k, CL = 2500pF
t HLD (Figure 1)
t LHD (Figure 1)
t HLR (Figure 2) (Normal Mode)
t LHR (Figure 2) (Normal Mode)
tHLR (Figure 2) (Receiver Alive Mode)
tLHR (Figure 2) (Receiver Alive Mode)
The ● denotes specifications which apply over the full operating
temperature range (0°C ≤ TA ≤ 70°C for Commercial grade and
– 40°C ≤ TA ≤ 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 VDREN and VRXEN = VCC.
MIN
120
30
3
●
●
●
●
●
●
UNITS
kbps
V/µs
V/µs
µs
µs
µs
µs
µs
µs
Note 3: Supply current measurement in Shutdown is performed with
VDREN and VRXEN = 0V.
Note 4: Supply current measurement in Receiver Alive mode is performed
with VDREN = 0V and VRXEN = VCC.
3
LTC1348
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TYPICAL PERFORMANCE CHARACTERISTICS
120kbps
250kbps
64kbps
OUTPUT HIGH
20kbps
VCC = 3.3V
0.1µF FLYING CAPACITORS
ALL DRIVERS LOADED 3kΩ + CL
1 DRIVER DRIVEN
OUTPUT LOW
64kbps 20kbps
120kbps
250kbps
0
3000
4000
1000
2000
LOAD CAPACITANCE (pF)
50
7
6
5
4
3
2
1
0
–1
–2
–3
–4
–5
–6
–7
120kbps
VCC = 3.3V
0.1µF FLYING CAPACITORS
ALL DRIVERS DRIVEN AND
LOADED 3kΩ + CL
OUTPUT LOW
3000
4000
1000
2000
LOAD CAPACITANCE (pF)
10
VCC = 3V
40
50
20
30
TEMPERATURE (°C)
60
45
VCC = 3.3V
16
ISC–
14
ISC+
12
10
8
6
250
VCC = 3.3V
35
30
25
20
VOUT = –20V
15
10
VOUT = 20V
5
4
70
150
200
100
DRIVER DATA RATE
40
LEAKAGE CURRENT (µA)
OUTPUT LOW
50
0
Driver Leakage in SHUTDOWN
vs Temperature (°C)
18
SHORT-CIRCUIT CURRENT (mA)
DRIVER OUTPUT VOLTAGE HIGH/LOW
VCC = 3V
ALL DRIVERS
LOADED WITH 3kΩ
0
5000
VCC = 3.3V
LTC1348 G03
20
VCC = 3.3V
0
Driver Short-Circuit Current
vs Temperature (°C)
OUTPUT HIGH
1 OUTPUT LOADED
3kΩ // 2500pF
20
LTC1348 G02
Driver Output Voltage High/Low
vs Temperature (°C)
VCC = 3.3V
30
10
64kbps
LTC1348 G01
7
6
5
4
3
2
1
0
–1
–2
–3
–4
–5
–6
–7
40
20kbps
0
5000
20kbps
OUTPUT HIGH
120kbps
3 OUTPUT LOADED
3kΩ // 2500pF
64kbps
SUPPLY CURRENT (mA)
7
6
5
4
3
2
1
0
–1
–2
–3
–4
–5
–6
–7
Supply Current
vs Driver Data Rate
Driver Output Voltage High/Low
vs Load Capacitance (CL)
DRIVER OUTPUT VOLTAGE HIGH/LOW
DRIVER OUTPUT VOLTAGE HIGH/LOW
Driver Output Voltage High/Low
vs Load Capacitance (CL)
0
–40
0
–20
0
20
40
60
TEMPERATURE (°C)
80
100
0
10
20
30
40
50
TEMPERATURE (°C)
60
70
LTC1348 G04
LTC1348 G05
With VCC = 3.3V
All Driver Outputs Loaded with
3kΩ, 1000pF. 1 Driven at 250kbps
DRIVEN DRIVER
OUTPUT
DRIVER
INPUT
LTC1348 G07
4
LTC1348 G06
LTC1348
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PI FU CTIO S
VCC: 3V to 5.5V Input Supply Pin. This pin should be
decoupled with a 0.1µF ceramic capacitor.
efficiency, the capacitor’s effective series resistance should
be less than 1Ω. Ceramic capacitors are recommended.
GND: Ground Pin.
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 VCC are
included on chip. To minimize power consumption, the
internal driver pull-up resistors are disconnected from VCC
in the Shutdown or Receiver Alive mode.
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 storage. The capacitor may be tied to ground or VCC. With
multiple devices, the V + and V – pins may be paralleled into
common capacitors. For large numbers of devices, increasing the size of the shared common storage capacitors is recommended to reduce ripple.
DR OUT: Driver Outputs at RS232 Voltage Levels. Outputs
are in a high impedance state when in the Shutdown,
Receiver Alive mode or VCC = 0V. The driver outputs are
protected against ESD to ±10kV for human body model
discharges.
V –: Negative Supply Output (RS232 Drivers). This pin
requires an external capacitor C = 0.1µF for charge
storage.
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.
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
RX OUT: Receiver Outputs with TTL/CMOS Voltage Levels. 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
Shutdown
0
0
All Drivers Shutdown.
All Driver Outputs Assume High Impedance.
All Driver Pull-Up Resistors Disconnect
From VCC.
All Receivers Shutdown.
All Receiver Outputs Assume High Impedance.
ICC TYP
Receiver
Disable
0
1
All Drivers Alive.
All Receiver Outputs in Three-State.
Receiver
Alive
1
0
All Drivers Shutdown.
All Driver Outputs in Three-State.
All Driver Pull-Up Resistors Disconnect
From VCC.
All Receivers Alive.
15µA
Normal
1
1
All Drivers Alive.
All Receivers Alive.
600µA at
3.3V,
800µA at
5V
0.2µA
600µA at
3.3V,
800µA at
5V
5
LTC1348
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SWITCHI G TI E WAVEFOR S
DRIVER
INPUT
VCC
1.4V
1.4V
0V
V+
DRIVER
OUTPUT
0V
0V
t LHD
V–
VCC
1.7V
RX
INPUT
RX
OUTPUT
1.3V
2.4V
0.8V
t LHR
t HLD
0V
t HLR
LTC1348 • F01
VCC
0V
LTC1348 • F02
Figure 1. Driver Propagation Delay Timing
Figure 2. Receiver Propagation Delay Timing
TEST CIRCUITS
ESD Test Circuit
DRIVER
OUTPUT
DRIVER
INPUT
DRIVER
V+
51pF
3k
0.1µF
0.1µF
VCC
LTC1348 • F03
28
LTC1348
3
26
RX
OUTPUT
RS232 LINE PINS
PROTECTED TO ±10kV
RX
51pF
LTC1348 • F04
0.1µF
0.1µF
–
25 C3
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
C2 – 4
6
C1–
7
DR1 OUT
8
RX1 IN
9
DR2 OUT
10
RX2 IN
11
RX3 IN
12
RX4 IN
13
DR3 OUT
14
RX5 IN
0.1µF
Figure 3. Driver Timing Test Load
V–
27 C3+
C1+ 5
0.1µF
RX INPUT
1
C2+ 2
LT1348 • TC
Figure 4. Receiver Timing Test Load
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APPLICATIONS INFORMATION
Power Supply
The LTC1348 includes an onboard voltage-tripling charge
pump capable of generating ±8V from a single 3.3V
supply. This allows the LTC1348 drivers to provide guaranteed ±5V RS232-compliant voltage levels with a 3.3V
supply. With all outputs loaded with 3kΩ, the LTC1348
can typically swing ±5V with voltages as low as 2.85V. It
will meet the ±3.7V EIA562 levels with supply voltages as
6
low as 2.2V. The charge pump requires three external
flying capacitors to operate; 0.1µF ceramic capacitors are
adequate for most applications. For applications requiring
extremely high data rates or abnormally heavy output
loads, 0.33µF flying capacitors are recommended. Bypass
and output capacitor values should match those of the
flying capacitors and all capacitors should be mounted as
close to the package as possible.
LTC1348
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APPLICATIONS INFORMATION
High Data Rates
The LTC1348 maintains true RS232 ±5V minimum driver
output even at high data rates. Figure 5 shows a test circuit
with 2m wires connecting the two test chips. Both chips
are run from 3.3V supplies. Figure 6 shows the typical line
waveforms with all three drivers, loaded with 1000pF and
3kΩ, toggling simultaneously at 120kbaud. Figure 7 shows
V+
1
+
C2 2
0.1µF
3
0.1µF
25
24
6
23
7
22
8
21
9
20
10
19
11
18
12
RX4 IN
DR3 OUT 13
17
14
15
1
28
DR1 OUT
C1–
RX1 IN
DR2 OUT
RX2 IN
RX3 IN
1000pF
27 C3+
RX5 IN
0.1µF
0.1µF
26
C2– 4
VCC
C1+ 5
0.1µF
V–
28
LTC1348
16
the same circuit with a single 1000pF/3kΩ loaded driver
driven at 250kbaud, and the other two drivers loaded but
not toggling. This closely approximates the actual behavior of an RS232 serial port, with only one driver (TX) driven
at high speed and the other two drivers (RTS and DTR)
driven at a relatively low data rate or at DC. Under the same
conditions, the LTC1348 can go as fast as 350kbaud and
still meet EIA562 (±3.7V) minimum driver output levels.
C3–
DR1 IN
RX1 OUT
DR2 IN
DRIVER OUTPUT
RX2 OUT
RX3 OUT
RX4 OUT
RECEIVER OUTPUT
DR3 IN
RX5 OUT
DREN
DRIVER INPUT
RXEN
GND
LTC1348 G06
V+
C2+ 2
0.1µF
0.1µF
3
C2–
4
VCC
C1+ 5
6
0.1µF
LTC1348
27 C3+
0.1µF
25
C3–
DRIVER 1 IN
24
23
1000pF
22
21
9
DR2 OUT
RX2 IN 10
20
11
18
12
17
13
16
14
15
RX3 IN
RX4 IN
DR3 OUT
RX5 IN
19
Figure 6. Driver Test Result at 120kbps
0.1µF
26
–
C1 7
DR1 OUT
RX1 IN 8
V–
RX1 OUT
DRIVER 2 IN
RX2 OUT
RX3 OUT
RX4 OUT
DRIVER 3 IN
DRIVER OUTPUT
RX5 OUT
DREN
RXEN
RECEIVER OUTPUT
GND
1000pF
LT1348 • F05
DRIVER INPUT
Figure 5. Data Rate Evaluation Circuit
LTC1348 G07
Figure 7. Driver Test Results at 250kbps
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
7
LTC1348
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PACKAGE DESCRIPTION
Dimensions in inches (millimeters) unless otherwise noted.
G Package
28-Lead Plastic SSOP (0.209)
(LTC DWG # 05-08-1640)
0.205 – 0.212**
(5.20 – 5.38)
0.397 – 0.407*
(10.07 – 10.33)
28 27 26 25 24 23 22 21 20 19 18 17 16 15
0.068 – 0.078
(1.73 – 1.99)
0° – 8°
0.005 – 0.009
(0.13 – 0.22)
0.0256
(0.65)
BSC
0.022 – 0.037
(0.55 – 0.95)
*DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
**DIMENSIONS DO NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
0.301 – 0.311
(7.65 – 7.90)
0.010 – 0.015
(0.25 – 0.38)
0.002 – 0.008
(0.05 – 0.21)
1 2 3 4 5 6 7 8 9 10 11 12 13 14
G28 SSOP 0694
SW Package
28-Lead Plastic Small Outline (Wide 0.300)
(LTC DWG # 05-08-1620)
0.697 – 0.712*
(17.70 – 18.08)
0.291 – 0.299**
(7.391 – 7.595)
0.010 – 0.029 × 45°
(0.254 – 0.737)
0.093 – 0.104
(2.362 – 2.642)
0.037 – 0.045
(0.940 – 1.143)
28
27
26
25
24
23
22
21
20
19
18
17
16
15
0° – 8° TYP
0.009 – 0.013
(0.229 – 0.330)
0.050
(1.270)
TYP
NOTE 1
0.014 – 0.019
0.016 – 0.050
(0.356 – 0.482)
(0.406 – 1.270)
NOTE:
1. PIN 1 IDENT, NOTCH ON TOP AND CAVITIES ON THE BOTTOM OF PACKAGES ARE THE MANUFACTURING OPTIONS.
THE PART MAY BE SUPPLIED WITH OR WITHOUT ANY OF THE OPTIONS
0.394 – 0.419
(10.007 – 10.643)
NOTE 1
0.004 – 0.012
(0.102 – 0.305)
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
1
2
3
4
5
6
7
8
9
10
11
12
13
14
S28 (WIDE) 0396
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DESCRIPTION
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3.3V Operation
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3-DR/5-RX RS232
3V Logic Interface
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5 Receivers Active in Shutdown
8
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417 ● (408) 432-1900
FAX: (408) 434-0507● TELEX: 499-3977 ● www.linear-tech.com
1348fa LT/GP 0197 5K REV A • PRINTED IN USA
LINEAR TECHNOLOGY CORPORATION 1994
工商网监
湘ICP备2023018690号
