1
LTC1318
Single 5V
RS232/RS422/AppleTalk
DCE Transceiver
DESCRIPTIO
N
U
s
Dual-Mode RS232/RS422 Peripherals
s
AppleTalk
Peripherals
s
Single 5V Systems
APPLICATIO
N
S
U
The LTC
1318 is a single 5V, RS232/RS422 transceiver
for connection to the DCE, or peripheral side of an interface
link. It includes an on-board charge pump to generate a
8V supply which allows true RS232 output swings. The
charge pump requires only four external 0.1
F capacitors.
The LTC1318 includes two RS232 drivers, a differential
RS422 driver, a dedicated RS232 receiver, and a pin
selectable RS232/RS422 receiver which can receive either
single-ended or differential signals.
The LTC1318 features driver outputs which can be taken
to common-mode voltages outside the power supply rails
without damage. Additionally, the driver outputs assume
a high impedance state when the power is shut off,
preventing externally applied signals from feeding back
into the power supplies. The RS232 devices will operate at
speeds up to 100kbaud. The RS422 devices will operate
up to 2Mbaud.
The LTC1318 is available in a 24-lead SO Wide package.
s
Single Chip Provides DCE RS232 or
RS422/AppleTalk
DCE Port
s
Operates from a Single 5V Supply
s
Charge Pump Uses 0.1
F Capacitors
s
Output Common-Mode Voltage Range Exceeds
Power Supply Rails for All Drivers
s
Driver Outputs Are High Impedance with Power Off
s
Pin Selectable RS232/RS422 Receiver
s
Thermal Shutdown Protection
s
Drivers Are Short-Circuit Protected
FEATURES
, LTC and LT are registered trademarks of Linear Technology Corporation.
AppleTalk and LocalTalk are registered trademarks of Apple Computer, Inc.
TYPICAL APPLICATIO
N
S
U
CHARGE
PUMP
RS232
LINES
APPLETALK
NETWORK
LOCALTALK
TRANSFORMER
100pF
4
22
22
22
22
22
22
22
22
V
+
C 1
+
C 1
RXI1
TXO1
TXO2
V
CC
R X D
+
R X D
/RXI2
T X D
+
T X D
NC
V
C 2
C 2
+
RXO1
TXI1
TXI2
GND
RXDO/RXO2
TXD
RXMODE
GND
NC
0.1
F
0.1
F
0.1
F
RS232
RS232
RS232
RS422
RS422
5V
1k
1k
0.1
F
LTC1318
TO
DIGITAL
SYSTEM
LT1318 TA01
RS232
R
L
= 100
200ns/DIV
1318 TA02
C
L
= 100pF
Driver Output Waveforms
TXD
(5V/DIV)
TXD
+
, TXD
(2V/DIV)
RXDO
(5V/DIV)
2
LTC1318
ABSOLUTE
M
AXI
M
U
M
RATINGS
W
W
W
PACKAGE/ORDER I
N
FOR
M
ATIO
N
W
U
U
Supply Voltage:
V
CC ......................................................................................
7V
V
+ ...................................................................................
13.2V
V
...............................................................................
13.2V
Input Voltage:
All Drivers .............................. 0.3 to (V
CC
+ 0.3V)
All Receivers ...................................... 25V to 25V
RXMODE Pin ....................... 0.3V to (V
CC
+ 0.3V)
Output Voltage:
RS232 Drivers ................ (V
+
30V) to (V
+ 30V)
RS422 Drivers ................................................
15V
All Receivers ........................ 0.3V to (V
CC
+ 0.3V)
Short-Circuit Duration:
V
+
or V
to GND .......................................... 30 sec
Driver or Receiver Outputs ...................... Indefinite
Operating Temperature Range .................... 0
C to 70
C
Lead Temperature (Soldering, 10 sec)................. 300
C
(Note 1)
ELECTRICAL CHARACTERISTICS
Consult factory for Industrial and Military grade parts
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Supplies
I
CC
Supply Current
No Load
q
9
30
mA
V
+
Positive Charge Pump Output Voltage
I
OUT
= 0mA
q
7.8
8.8
V
I
OUT
= 10mA, V
CC
= 5V
q
6.8
7.4
V
V
Negative Charge Pump Output Voltage
I
OUT
= 0mA
q
7.3
8.6
V
I
OUT
= 5mA, V
CC
= 5V
q
6.3
7.3
V
Differential Driver
V
OD
Differential Driver Output Voltage
No Load (Figure 1)
q
4
V
R
L
= 100
(Figure 1)
q
2
V
DV
OD
Change in Magnitude of Differential
R
L
= 100
(Figure 1)
q
0.2
V
Output Voltage
V
OC
Common-Mode Output Voltage
R
L
= 100
(Figure 1)
q
3
V
I
DSS
Short-Circuit Output Current
1V < V
CMR
< 7V
q
35
200
mA
V
IL
Input Low Voltage
q
0.8
V
V
IH
Input High Voltage
q
2.0
V
Single-Ended Driver
V
O
Output Voltage Swing
R
L
= 3k
q
5
7.3/6.5
V
I
OSS
Short-Circuit Output Current
V
OUT
= OV
q
5
17
mA
V
IL
Input Low Voltage
q
0.8
V
V
IH
Input High Voltage
q
2
V
SR
Output Slew Rate
R
L
= 3k,
C
L
= 51pF
q
4
20
30
V/
S
T
JMAX
= 125
C,
JA
= 85
C/W
V
S
= 5V
5%, C1 = C2 = 0.1
F, T
A
= 0
C to 70
C, unless otherwise specified. (Notes 2, 3)
1
2
3
4
5
6
7
8
9
10
11
12
TOP VIEW
SW PACKAGE
24-LEAD PLASTIC SO WIDE
24
23
22
21
20
19
18
17
16
15
14
13
V
+
C 1
+
C 1
RXI1
TXO1
TXO2
V
CC
R X D
+
R X D
/RXI2
T X D
+
T X D
NC
V
C 2
C 2
+
RXO1
TXI1
TXI2
GND
RXDO/RXO2
TXD
RXMODE
GND
NC
ORDER PART
NUMBER
LTC1318CSW
3
LTC1318
ELECTRICAL CHARACTERISTICS
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Differential Receiver
V
TH
Differential Receiver Threshold
q
0.2
0.2
V
CMR
Common-Mode Input Range
q
7
7
V
Hysteresis
V
CM
= OV
q
30
mV
R
IN
Input Resistance
TA = 25
C
3
5
7
k
V
OL
Output Low Voltage
I
OUT
= 1.6mA
0.4
V
V
OH
Output High Voltage
I
OUT
= 160
A, V
CC
= 5V
q
3.5
V
I
OSS
Short-Circuit Output Current
V
O
= GND or V
CC
q
7
85
mA
Single-Ended Receiver
V
L
Input Voltage Low Threshold
q
0.8
1.4
V
V
IH
Input Voltage High Threshold
q
1.8
2.4
V
Hysteresis
q
0.1
0.4
1.0
V
R
IN
Input Resistance
TA = 25
C
3
5
7
k
V
OL
Output Low Voltage
I
OUT
= 4mA
q
0.2
0.4
V
V
OH
Output High Voltage
I
OUT
= 4mA, V
CC
= 5V
q
3.5
4.8
V
I
OSS
Short-Circuit Output Current
V
O
= GND or V
CC
q
7
85
mA
V
ILRXM
RXMODE Input Low Voltage
q
0.8
1.6
V
V
IHRXM
RXMODE Input High Voltage
q
1.6
2.0
V
I
INRXM
RXMODE Input Current
V
IN
= OV or V
CC
q
2
A
Switching Characteristics
t
PLH,HL
Differential Driver Propagation Delay
R
L
= 100
, C
L
= 100pF (Figures 2,3)
q
35
100
ns
t
SKEW
Differential Driver Output to Output
R
L
= 100
, C
L
= 100pF (Figures 2,3)
q
5
35
ns
t
R,F
Differential Driver Rise, Fall Time
R
L
= 100
, C
L
= 100pF (Figures 2,3)
q
15
50
ns
t
PLH,HL
Differential Receiver Propagation Delay
C
L
= 15pF, (Figures 4)
q
110
200
ns
t
SEL
Receiver Mode Switching Time
q
25
100
ns
The
q
denotes specifications which apply over the full operating
temperature range.
Note 1: Absolute maximum ratings are those values beyond which the life
of the device may be impaired.
Note 2: All currents into device pins are negative, all currents out of device
pins are positive. All voltages are referenced to ground unless otherwise
specified.
Note 3: All typicals are given at V
CC
= 5V, T
A
= 25
C.
V
S
= 5V
5%, C1 = C2 = 0.1
F, T
A
= 0
C to 70
C, unless otherwise specified. (Notes 2, 3)
4
LTC1318
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
LOAD CURRENT (mA)
0
CHARGE PUMP OUTPUT VOLTAGE (V)
10
8
6
4
2
0
2
4
6
8
10
12
1318 G02
3
6
9
15
V
+
V
T
A
= 25
C
V
CC
= 5V
I
LOAD
= V
+
TO V
TEMPERATURE (
C)
0
SUPPLY CURRENT (mA)
10.0
9.8
9.6
9.4
9.2
9.0
8.8
8.6
8.4
8.2
8.0
20
40
50
1318 G01
10
30
60
70
V
CC
= 5V
Charge Pump Output Voltage
vs Load Current
TEMPERATURE (
C)
0
THRESHOLD VOLTAGE (V)
60
1318 G03
20
40
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
10
30
50
70
V
CC
= 5V
INPUT HIGH (TXI1, TXI2)
INPUT HIGH (TXD)
INPUT LOW (TXD)
INPUT LOW (TXI1, TXI2)
TTL Input Threshold
vs Temperature
RS422 Driver Single-Ended
Output Swing vs Load Current
Supply Current vs Temperature
RS422 Driver Short-Circuit
Current vs Temperature
LOAD CURRENT (mA)
0
DIFFERENTIAL OUTPUT SWING (V)
10
9
8
7
6
5
4
3
2
1
0
1318 G04
10
20 30
40 50
60 70
80 90 100
T
A
= 25
C
V
CC
= 5V
I
LOAD
FROM
TXD
+
TO TXD
LOAD CURRENT (mA)
0
DRIVER OUTPUT SWING (V)
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
1318 G05
10
20 30
40 50
60 70
80 90 100
T
A
= 25
C
V
CC
= 5V
I
LOAD
FROM TXD
+
,
TXD
TO GND
TEMPERATURE (
C)
0
SHORT-CIRCUIT CURRENT (mA)
100
98
96
94
92
90
88
86
84
82
80
20
40
50
1318 G06
10
30
60
70
V
CC
= 5V
I
SC
+
I
SC
RS422 Driver Differential Output
Swing vs Load Current
RS232 Driver Output Swing vs
Resistive Load
RS232 Driver Slew Rate vs
Load Capacitance
RS232 Driver Short-Circuit
Current vs Temperature
RESISTIVE LOAD (k
)
1
DRIVER OUTPUT SWING (V)
10
8
6
4
2
0
2
4
6
8
10
3
10
1318 G08
2
4
5
6 7 8 9
T
A
= 25
C
V
CC
= 5V
POSITIVE SWING
NEGATIVE SWING
CAPACITANCE (pF)
10
SLEW RATE (V/
s)
25
20
15
10
5
0
100
1000
10000
1318 G07
SR
SR
+
T
A
= 25
C
V
CC
= 5V
TEMPERATURE (
C)
0
SHORT-CIRCUIT CURRENT (mA)
20.0
19.5
19.0
18.5
18.0
17.5
17.0
16.5
16.0
15.5
15.0
20
40
50
1318 G09
10
30
60
70
V
CC
= 5V
I
SC
+
I
SC
5
LTC1318
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
TEMPERATURE (
C)
0
THRESHOLD VOLTAGE (mV)
60
1318 G10
20
40
100
90
80
70
60
50
40
30
20
10
30
50
70
INPUT HIGH
INPUT LOW
V
CC
= 5V
TEMPERATURE (
C)
0
24
22
20
18
16
14
12
10
30
50
1318 G12
10
20
40
60
70
SHORT-CIRCUIT CURRENT (mA)
RXO1
V
CC
= 5V
RXDO/RXO2
TEMPERATURE (
C)
0
THRESHOLD VOLTAGE (V)
60
1318 G11
20
40
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
10
30
50
70
INPUT HIGH (RXDO/RXO2)
INPUT HIGH (RXO1)
INPUT LOW (RXO1)
V
CC
= 5V
INPUT LOW (RXDO/RXO2)
TTL Output Short-Circuit Current
vs Temperature
RS232 Receiver Input Threshold
vs Temperature
V
+
(Pin 1): Charge Pump Positive Output. This pin re-
quires a 0.1
F capacitor to ground. Under normal opera-
tion this pin maintains a voltage of about 8.8V above
ground. An external load can be connected between this
pin and ground or V
.
C1
+
, C1
(Pins 2, 3): C1 Inputs. Connect a 0.1
F capacitor
between C1
+
and C1
.
RXI1 (Pin 4): First RS232 Single-Ended Receiver Input.
This is an inverting receiver.
TXO1, TXO2 (Pins 5,6): RS232 Single-Ended Driver Out-
puts.
V
CC
(Pin 7): Positive Supply Input. Apply 4.75V
V
CC
5.25V to this pin. A 0.1
F bypass capacitor is required.
RXD
+
(Pin 8): When RXMODE (pin 15) is low, this pin acts
as the differential RS422 receiver positive input. When
RXMODE is high, this pin is disabled.
RXD
/RXI2 (Pin 9): When RXMODE (pin 15) is low, this
pin acts as the differential RS422 receiver negative input.
When RXMODE is high, this pin acts as the second RS232
receiver input. The receiver is inverting in RS232 mode.
TXD
+
(Pin 10): Differential RS422 Driver Noninverting
Output.
PI
N
FU
N
CTIO
N
S
U
U
U
TXD
(Pin 11): Differential RS422 Driver Inverting Output.
NC (Pins 12,13): No Internal Connection.
GND (Pins 14, 18): Power Supply Ground. Connect both
pins to each other and to the ground.
RXMODE (Pin 15): This pin controls the state of the
differential/single-ended receiver. When RXMODE is low,
the receiver is in differential mode and will receive RS422
compatible signals at RXD
+
and RXD
/RXI2 (pins 8
and 9). When RXMODE goes high, the receiver enters
single-ended mode and will receive RS232 compatible
signals at RXD
/RXI2. RXD
+
is disabled in single-ended
mode. Both modes use the RXDO/RXO2 pin (pin 17) as
their output.
TXD (Pin 16): Differential RS422 Driver Input (TTL Com-
patible).
RXDO/RXO2 (Pin 17): This is the output of the configurable
differential/single-ended receiver.
TXI1, TXI2 (Pins 20, 19): RS232 Driver Inputs (TTL
Compatible). Both are inverting inputs.
RXO1 (Pin 21): First RS232 Receiver Outputs (TTL com-
patible).
RS422 Receiver Differential
Threshold vs Temperature
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