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LTC1348 3.3V/5V Low Power RS232 3-Driver/5-Receiver Transceiver
FEATURES
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DESCRIPTIO
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Low Supply Current: 600A at 3.3V Supply Current in Shutdown: 0.2A Supply Current in Receiver Alive Mode: 15A ESD Protection over 10kV Operates from a Single 3V to 5.5V Supply Operates to 120kBaud with 0.1F 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(R)1348 is a 3-driver/5-receiver RS232 transceiver with very low supply current. The charge pump only requires five 0.1F 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 600A at 3.3V and 800A at 5V in the no load condition. In Shutdown mode, the supply current is further reduced to 0.2A. In Receiver Alive mode, all five receivers are kept alive and the supply current is 15A. 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, 3k. 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
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Notebook Computers Palmtop Computers Printers Portable Instruments
TYPICAL APPLICATI
V+ C5 0.1F C2 0.1F VCC C1 0.1F 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 0.1F 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 0.1F
SUPPLY CURRENT (mA)
1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 -40 -20 VCC = 5V VCC = 3.3V VCC = 3.3V OR 5V SHUTDOWN CURRENT QUIESCENT CURRENT
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Supply Current
1.6 1.4
SHUTDOWN CURRENT (A)
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)
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RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW V+ C2 - 1 3 28 V- C2 + 2 VCC 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 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 (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................................................ 0C to 70C LTC1348I............................................ - 40C to 85C Storage Temperature Range ................ - 65C to 150C Lead Temperature (Soldering, 10 sec)................. 300C
ORDER PART NUMBER LTC1348CG LTC1348CSW LTC1348IG LTC1348ISW
TJMAX = 125C, JA = 96C/W (G) TJMAX = 125C, JA = 85C/W (SW)
Consult factory for Military grade parts.
DC ELECTRICAL CHARACTERISTICS
VCC = 3V to 5.5V, C1 to C4 = 0.1F, unless otherwise noted.
PARAMETER Any Driver Output Voltage Swing Logic Input Voltage Level CONDITIONS VCC = 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 A A mA A
Logic Input Current Output Short-Circuit Current Output Leakage Current Any Receiver Input Voltage Thresholds
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 = 160A Sinking Current, VOUT = VCC Shutdown (Note 3), 0V VOUT VCC
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
VCC - 0.6V -3
10
2
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V V V V k V V mA A
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LTC1348
DC ELECTRICAL CHARACTERISTICS
VCC = 3V to 5.5V, C1 to C4 = 0.1F, unless otherwise noted.
PARAMETER Power Supply Generator V + Output Voltage V - Output Voltage Supply Rise Time Power Supply VCC Supply Current CONDITIONS IOUT = 0mA IOUT = 8mA IOUT = 0mA IOUT = - 8mA Shutdown to Turn-On 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) VCC = 3.3V VCC = 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 (VCC) 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 A A V V V
AC ELECTRICAL CHARACTERISTICS
VCC = 3V to 5.5V, C1 to C4 = 0.1F, 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) 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/s V/s s s s s s s
The q denotes specifications which apply over the full operating temperature range (0C TA 70C for Commercial grade and - 40C TA 85C 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.
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
TYPICAL PERFORMANCE CHARACTERISTICS
Driver Output Voltage High/Low vs Load Capacitance (CL)
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 VCC = 3.3V 0.1F FLYING CAPACITORS ALL DRIVERS LOADED 3k + CL 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
VCC = 3.3V OUTPUT HIGH
SHORT-CIRCUIT CURRENT (mA)
LEAKAGE CURRENT (A)
ALL DRIVERS LOADED WITH 3k
OUTPUT LOW VCC = 3.3V VCC = 3V
10
40 50 20 30 TEMPERATURE (C)
4
UW
VCC = 3V 60 70
Driver Output Voltage High/Low vs Load Capacitance (CL)
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 3k // 2500pF 40
120kbps
64kbps OUTPUT HIGH 20kbps
VCC = 3.3V 0.1F FLYING CAPACITORS ALL DRIVERS DRIVEN AND LOADED 3k + CL OUTPUT LOW 120kbps 64kbps 20kbps 3000 4000 1000 2000 LOAD CAPACITANCE (pF) 5000
LTC1348 G02
30 1 OUTPUT LOADED 3k // 2500pF
20
10 VCC = 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 VCC = 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 ISC+ ISC-
Driver Leakage in SHUTDOWN vs Temperature (C)
VCC = 3.3V
VOUT = -20V
VOUT = 20V
0
10
20 30 40 50 TEMPERATURE (C)
60
70
LTC1348 G04
LTC1348 G05 LTC1348 G06
With VCC = 3.3V All Driver Outputs Loaded with 3k, 1000pF. 1 Driven at 250kbps
DRIVEN DRIVER OUTPUT
DRIVER INPUT
LTC1348 G07
LTC1348
PI FU CTIO S
VCC: 3V to 5.5V Input Supply Pin. This pin should be decoupled with a 0.1F 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 = 0.1F 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. V -: Negative Supply Output (RS232 Drivers). This pin requires an external capacitor C = 0.1F for charge storage. C1+, C1-, C2+, C2-, C3+, C3-: Commutating Capacitor Inputs. These pins require three external capacitors C = 0.1F: 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 VCC. All Drivers Alive. RECEIVERS All Receivers Shutdown. All Receiver Outputs Assume High Impedance. ICC TYP 0.2A
Receiver Disable
0
Receiver Alive
1
Normal
1
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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 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. 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. 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 Levels. 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.
600A at 3.3V, 800A at 5V 15A
0
All Drivers Shutdown. All Driver Outputs in Three-State. All Driver Pull-Up Resistors Disconnect From VCC. All Drivers Alive.
All Receivers Alive.
1
All Receivers Alive.
600A at 3.3V, 800A at 5V
5
LTC1348
SWITCHI G TI E WAVEFOR S
DRIVER INPUT DRIVER OUTPUT t LHD VCC 1.4V 1.4V 0V V+ 0V t HLD
LTC1348 * F01
Figure 1. Driver Propagation Delay Timing
TEST CIRCUITS
DRIVER INPUT DRIVER OUTPUT DRIVER 51pF 3k
LTC1348 * F03
Figure 3. Driver Timing Test Load
RX OUTPUT RX INPUT RX 51pF
LTC1348 * F04
Figure 4. Receiver Timing Test Load
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 3k, 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 low as 2.2V. The charge pump requires three external flying capacitors to operate; 0.1F ceramic capacitors are adequate for most applications. For applications requiring extremely high data rates or abnormally heavy output loads, 0.33F 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.
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RX INPUT RX OUTPUT t LHR
1.7V
VCC 1.3V 0V 2.4V VCC 0V
LTC1348 * F02
0V
V-
0.8V t HLR
Figure 2. Receiver Propagation Delay Timing
ESD Test Circuit
V+ 0.1F 0.1F VCC 0.1F 0.1F 1 C2+ 2 3 C2 - 4 C1+ 5 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
LT1348 * TC
28 LTC1348 27 C3+ 26
V- 0.1F 0.1F
RS232 LINE PINS PROTECTED TO 10kV
- 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
LTC1348 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 3k, toggling simultaneously at 120kbaud. Figure 7 shows
V+ 0.1F 0.1F
+
1 C2 2 3 LTC1348
28 27 C3+ 26 25 24 23 22 21 20 19 18 17 16 15
V- 0.1F 0.1F C3- DR1 IN RX1 OUT DR2 IN RX2 OUT RX3 OUT RX4 OUT DR3 IN RX5 OUT DREN RXEN GND
LTC1348 G06
C2- 4 VCC C1+ 5 0.1F DR1 OUT C1- 6 7 8 9 10 11
RX1 IN DR2 OUT RX2 IN RX3 IN
12 RX4 IN DR3 OUT 13 1000pF RX5 IN 14
V+ 0.1F 0.1F
1 C2+ 2 3 LTC1348
28 27 C3+ 26 25 24 23 22 21 20 19 18 17 16 15
V- 0.1F 0.1F C3- DRIVER 1 IN RX1 OUT DRIVER 2 IN RX2 OUT RX3 OUT RX4 OUT DRIVER 3 IN RX5 OUT DREN RXEN GND
LT1348 * F05
C2- 4 VCC C1+ 5 0.1F
-
6
C1 7 DR1 OUT RX1 IN 8 9 DR2 OUT RX2 IN 10 1000pF RX3 IN RX4 IN DR3 OUT RX5 IN 1000pF 11 12 13 14
Figure 5. Data Rate Evaluation Circuit
LTC1348 G07
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.
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the same circuit with a single 1000pF/3k 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.
DRIVER OUTPUT
RECEIVER OUTPUT
DRIVER INPUT
Figure 6. Driver Test Result at 120kbps
DRIVER OUTPUT
RECEIVER OUTPUT
DRIVER INPUT
Figure 7. Driver Test Results at 250kbps
7
LTC1348
PACKAGE DESCRIPTION
0.205 - 0.212** (5.20 - 5.38)
0 - 8 0.301 - 0.311 (7.65 - 7.90) 0.002 - 0.008 (0.05 - 0.21)
0.005 - 0.009 (0.13 - 0.22)
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
0.291 - 0.299** (7.391 - 7.595) 0.010 - 0.029 x 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
0 - 8 TYP
0.009 - 0.013 (0.229 - 0.330)
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 *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
NOTE 1
0.050 (1.270) TYP
RELATED PARTS
PART NUMBER LT1137A LTC1327 LT1330 LT1331 LTC1347 DESCRIPTION 3-DR/5-RX RS232 Transceiver 3-DR/5-RX RS562 Transceiver 3-DR/5-RX RS232 3-DR/5-RX RS232/RS562 Transceiver 3-DR/5-RX Micropower RS232 Transceiver COMMENTS 15kV IEC-801-2 ESD Protection 3.3V Operation 3V Logic Interface 5V RS232 or 3V RS562 Operation 5 Receivers Active in Shutdown
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Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417 q (408) 432-1900 FAX: (408) 434-0507q TELEX: 499-3977 q www.linear-tech.com
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Dimensions in inches (millimeters) unless otherwise noted. G Package 28-Lead Plastic SSOP (0.209)
(LTC DWG # 05-08-1640)
0.068 - 0.078 (1.73 - 1.99)
0.397 - 0.407* (10.07 - 10.33) 28 27 26 25 24 23 22 21 20 19 18 17 16 15
0.0256 (0.65) BSC
0.010 - 0.015 (0.25 - 0.38)
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) 23 22 21 20 19 18 17 16 15
NOTE 1 0.004 - 0.012 (0.102 - 0.305)
0.394 - 0.419 (10.007 - 10.643)
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2
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5
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S28 (WIDE) 0396
1348fa LT/GP 0197 5K REV A * PRINTED IN USA
(c) LINEAR TECHNOLOGY CORPORATION 1994

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