LTC1318
Single 5V
RS232/RS422/AppleTalk
®
DCE Transceiver
FEATURES
s
s
s
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DESCRIPTION
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 0.1µF 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.
, LTC and LT are registered trademarks of Linear Technology Corporation.
AppleTalk and LocalTalk are registered trademarks of Apple Computer, Inc.
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s
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Single Chip Provides DCE RS232 or
RS422/AppleTalk DCE Port
Operates from a Single 5V Supply
Charge Pump Uses 0.1µF Capacitors
Output Common-Mode Voltage Range Exceeds
Power Supply Rails for All Drivers
Driver Outputs Are High Impedance with Power Off
Pin Selectable RS232/RS422 Receiver
Thermal Shutdown Protection
Drivers Are Short-Circuit Protected
APPLICATIONS
s
s
s
Dual-Mode RS232/RS422 Peripherals
AppleTalk Peripherals
Single 5V Systems
TYPICAL APPLICATIONS
V
+
0.1µF
0.1µF
C1
+
C1
–
RXI1 RS232
RS232
LINES
TXO1 RS232
TXO2 RS232
5V
1k
22Ω
22Ω
V
CC
RXD
+
RXD
–
/RXI2
1k
APPLETALK
NETWORK
22Ω
22Ω
TXD
+
RS232
RS422
CHARGE
PUMP
V
–
C2
–
C2
+
RXO1
TXI1
TXI2
GND
RXDO/RXO2
TXD
RXMODE
GND
LTC1318
NC
LT1318 • TA01
0.1µF
0.1µF
TXD
(5V/DIV)
TO
DIGITAL
SYSTEM
TXD
+
, TXD
–
(2V/DIV)
RXDO
(5V/DIV)
TXD
–
RS422
22Ω
22Ω
NC
22Ω
LOCALTALK
®
TRANSFORMER
22Ω
100pF
×
4
U
U
U
Driver Output Waveforms
R
L
= 100Ω
C
L
= 100pF
200ns/DIV
1318 TA02
1
LTC1318
ABSOLUTE
MAXIMUM
RATINGS
(Note 1)
PACKAGE/ORDER INFORMATION
TOP VIEW
V
+
1
C1
+
2
C1
–
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
24 V
–
23 C2
–
22 C2
+
21 RXO1
20 TXI1
19 TXI2
18 GND
17 RXDO/RXO2
16 TXD
15 RXMODE
14 GND
13 NC
ORDER PART
NUMBER
LTC1318CSW
3
RXI1 4
TXO1 5
TXO2 6
V
CC
7
RXD
+
8
RXD
–
/RXI2 9
TXD
+
10
TXD
–
11
NC 12
SW PACKAGE
24-LEAD PLASTIC SO WIDE
T
JMAX
= 125°C,
θ
JA
= 85°C/W
Consult factory for Industrial and Military grade parts
ELECTRICAL CHARACTERISTICS
V
S
= 5V
±5%,
C1 = C2 = 0.1µF, T
A
= 0°C to 70°C, unless otherwise specified. (Notes 2, 3)
SYMBOL
Supplies
I
CC
V
+
V
–
Supply Current
Positive Charge Pump Output Voltage
Negative Charge Pump Output Voltage
No Load
I
OUT
= 0mA
I
OUT
= 10mA, V
CC
= 5V
I
OUT
= 0mA
I
OUT
= – 5mA, V
CC
= 5V
No Load (Figure 1)
R
L
= 100Ω (Figure 1)
R
L
= 100Ω (Figure 1)
R
L
= 100Ω (Figure 1)
– 1V < V
CMR
< 7V
q
q
q
q
q
PARAMETER
CONDITIONS
MIN
TYP
9
MAX
30
UNITS
mA
V
V
V
V
V
V
7.8
6.8
–7.3
– 6.3
±4
±2
8.8
7.4
–8.6
–7.3
Differential Driver
V
OD
DV
OD
V
OC
I
DSS
V
IL
V
IH
V
O
I
OSS
V
IL
V
IH
SR
Differential Driver Output Voltage
Change in Magnitude of Differential
Output Voltage
Common-Mode Output Voltage
Short-Circuit Output Current
Input Low Voltage
Input High Voltage
Output Voltage Swing
Short-Circuit Output Current
Input Low Voltage
Input High Voltage
Output Slew Rate
R
L
= 3k, C
L
= 51pF
R
L
= 3k
V
OUT
= OV
q
q
q
q
q
q
q
0.2
3
35
2.0
±5
±5
2
4
20
30
7.3/–6.5
17
0.8
200
0.8
mA
V
V
V
mA
V
V
V/µS
Single-Ended Driver
q
q
q
q
q
2
U
V
V
W
U
W W
W
LTC1318
ELECTRICAL CHARACTERISTICS
V
S
= 5V
±5%,
C1 = C2 = 0.1µF, T
A
= 0°C to 70°C, unless otherwise specified. (Notes 2, 3)
SYMBOL
V
TH
CMR
R
IN
V
OL
V
OH
I
OSS
V
L
V
IH
R
IN
V
OL
V
OH
I
OSS
V
ILRXM
V
IHRXM
I
INRXM
t
PLH,HL
t
SKEW
t
R,F
t
PLH,HL
t
SEL
PARAMETER
Differential Receiver Threshold
Common-Mode Input Range
Hysteresis
Input Resistance
Output Low Voltage
Output High Voltage
Short-Circuit Output Current
Input Voltage Low Threshold
Input Voltage High Threshold
Hysteresis
Input Resistance
Output Low Voltage
Output High Voltage
Short-Circuit Output Current
RXMODE Input Low Voltage
RXMODE Input High Voltage
RXMODE Input Current
Differential Driver Propagation Delay
Differential Driver Output to Output
Differential Driver Rise, Fall Time
Differential Receiver Propagation Delay
Receiver Mode Switching Time
V
IN
= OV or V
CC
R
L
= 100Ω, C
L
= 100pF (Figures 2,3)
R
L
= 100Ω, C
L
= 100pF (Figures 2,3)
R
L
= 100Ω, C
L
= 100pF (Figures 2,3)
C
L
= 15pF, (Figures 4)
TA = 25°C
I
OUT
= –4mA
I
OUT
= 4mA, V
CC
= 5V
V
O
= GND or V
CC
q
q
q
q
q
q
CONDITIONS
q
q
MIN
– 0.2
–7
TYP
MAX
0.2
7
UNITS
V
V
mV
kΩ
V
V
mA
V
Differential Receiver
V
CM
= OV
TA = 25°C
I
OUT
= –1.6mA
I
OUT
= 160µA, V
CC
= 5V
V
O
= GND or V
CC
q
30
3
5
7
0.4
q
q
3.5
±7
0.8
0.1
3
3.5
±7
0.8
1.6
1.6
2.0
±2
35
5
15
110
25
100
35
50
200
100
1.4
1.8
0.4
5
0.2
4.8
±85
2.4
1.0
7
0.4
±85
Single-Ended Receiver
q
q
q
V
V
kΩ
V
–V
mA
V
V
µA
ns
ns
ns
ns
ns
Switching Characteristics
q
q
q
q
q
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.
3
LTC1318
TYPICAL PERFORMANCE CHARACTERISTICS
Supply Current vs Temperature
10.0
CHARGE PUMP OUTPUT VOLTAGE (V)
9.8
9.6
V
CC
= 5V
THRESHOLD VOLTAGE (V)
SUPPLY CURRENT (mA)
9.4
9.2
9.0
8.8
8.6
8.4
8.2
8.0
0
10
40
30
20
50
TEMPERATURE (°C)
60
70
RS422 Driver Differential Output
Swing vs Load Current
10
DIFFERENTIAL OUTPUT SWING (V)
9
8
7
6
5
4
3
2
1
0
0
SHORT-CIRCUIT CURRENT (mA)
DRIVER OUTPUT SWING (V)
T
A
= 25°C
V
CC
= 5V
I
LOAD
FROM
TXD
+
TO TXD
–
10 20 30 40 50 60 70 80 90 100
LOAD CURRENT (mA)
1318 G04
RS232 Driver Slew Rate vs
Load Capacitance
25
T
A
= 25°C
V
CC
= 5V
SLEW RATE (V/µs)
SR
–
15
SR
+
DRIVER OUTPUT SWING (V)
20
6
4
2
0
–2
–4
–6
–8
NEGATIVE SWING
T
A
= 25°C
V
CC
= 5V
SHORT-CIRCUIT CURRENT (mA)
10
5
0
10
100
1000
CAPACITANCE (pF)
10000
1318 G07
4
U W
1318 G01
Charge Pump Output Voltage
vs Load Current
10
8
6
4
2
0
–2
–4
–6
–8
–10
0
3
9
12
6
LOAD CURRENT (mA)
15
1318 G02
TTL Input Threshold
vs Temperature
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0
10
20
30
40
50
60
70
TEMPERATURE (°C)
1318 G03
V
+
V
CC
= 5V
INPUT HIGH (TXI1, TXI2)
INPUT HIGH (TXD)
T
A
= 25°C
V
CC
= 5V
I
LOAD
= V
+
TO V
–
INPUT LOW (TXD)
INPUT LOW (TXI1, TXI2)
V
–
RS422 Driver Single-Ended
Output Swing vs Load Current
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
0
10
20 30 40 50 60 70 80 90 100
LOAD CURRENT (mA)
1318 G05
RS422 Driver Short-Circuit
Current vs Temperature
100
98
96
94
92
90
88
86
84
82
80
0
10
40
30
20
50
TEMPERATURE (°C)
60
70
I
SC+
I
SC–
V
CC
= 5V
T
A
= 25°C
V
CC
= 5V
I
LOAD
FROM TXD
+
,
TXD
–
TO GND
1318 G06
RS232 Driver Output Swing vs
Resistive Load
10
8
POSITIVE SWING
20.0
19.5
19.0
18.5
18.0
17.5
17.0
16.5
16.0
15.5
15.0
RS232 Driver Short-Circuit
Current vs Temperature
V
CC
= 5V
I
SC–
I
SC+
–10
1
3
2
4 5 6 7 8 9 10
RESISTIVE LOAD (kΩ)
1318 G08
0
10
40
30
20
50
TEMPERATURE (°C)
60
70
1318 G09
LTC1318
TYPICAL PERFORMANCE CHARACTERISTICS
RS422 Receiver Differential
Threshold vs Temperature
100
90
V
CC
= 5V
THRESHOLD VOLTAGE (V)
SHORT-CIRCUIT CURRENT (mA)
THRESHOLD VOLTAGE (mV)
80
70
60
50
40
30
20
0
10
20
30
INPUT HIGH
INPUT LOW
40
50
TEMPERATURE (°C)
1318 G10
PIN FUNCTIONS
V
+
(Pin 1):
Charge Pump Positive Output. This pin re-
quires a 0.1µF 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 0.1µF 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 0.1µF 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.
(Pin 10):
Differential RS422 Driver Noninverting
Output.
TXD
+
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).
U W
60
RS232 Receiver Input Threshold
vs Temperature
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
70
0
10
20
30
40
50
60
70
TEMPERATURE (°C)
1318 G11
TTL Output Short-Circuit Current
vs Temperature
24
V
CC
= 5V
22
20
18
RXDO/RXO2
16
14
12
10
0
10
40
30
50
20
TEMPERATURE (°C)
60
70
V
CC
= 5V
INPUT HIGH (RXDO/RXO2)
INPUT HIGH (RXO1)
RXO1
INPUT LOW (RXO1)
INPUT LOW (RXDO/RXO2)
1318 G12
U
U
U
5
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