LT1080/LT1081
Advanced Low Power
5V RS232 Dual Driver/Receiver
FEATURES
s
DESCRIPTIO
s
s
s
s
s
s
Superior to CMOS
– Improved Speed: Operates over 120kBaud
– Improved Protection: Outputs Can Be Forced
to
±30V
without Damage
– Three-State Outputs Are High
Impedance When Off
– Only Needs 1µF Capacitors
Absolutely No Latchup
CMOS Comparable Low Power: 60mW
Can Power Additional RS232 Drivers: 10mA
Supply Current in Shutdown: 1µA
Available in SO Package
Available with or without Shutdown
The LT
®
1080/LT1081 are the only dual RS232 driver/
receiver with charge pump to guarantee absolutely no
latchup. These interface optimized devices provide a real-
istic balance between CMOS levels of power dissipation
and real world requirements for ruggedness. The driver
outputs are fully protected against overload and can be
shorted to
±30V.
Unlike CMOS, the advanced architecture
of the LT1080/LT1081 does not load the signal line when
“shut down” or when power is off. Both the receiver and
RS232 outputs are put into a high impedance state. An
advanced output stage allows driving higher capacitive
loads at higher speeds with exceptional ruggedness
against ESD.
For applications requiring up to five drivers and five
receivers with charge pump in one package see the LT1130A
Series data sheet. A version of the LT1080/LT1081, the
LT1180A and LT1181A that use only 0.1µF capacitors, is
also available. All of Linear Technology’s RS232 ICs are
available in standard surface mount packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
s
s
s
s
s
Portable Computers
Battery-Powered RS232 Systems
Power Supply Generator
Terminals
Modems
TYPICAL APPLICATIO
2
1µF
4
LT1080
5
1µF
6
12
LOGIC
INPUTS
15
7
17
3
5V INPUT
9V OUTPUT
1µF
–9V OUTPUT
Supply Generator Outputs
10
8
R
L
TO V
–
V
+
OUTPUT
R
L
TO GND
OUTPUT VOLTAGE (V)
1µF
RS232 OUTPUT
6
4
2
0
–2
–4
–6
V
CC
= 5V
11
13
8
14
5k
RS232 OUTPUT
RS232 INPUT
LOGIC
OUTPUTS
10
18
R
L
TO V
+
V
–
OUTPUT
0
2
4
9
5k
16
–8
RS232 INPUT
–10
ON/OFF
1080/81 • TA01
U
R
L
TO GND
6 8 10 12 14 16 18 20
OUTPUT CURRENT (mA)
1080/81 TA01a
U
U
1
LT1080/LT1081
ABSOLUTE
AXI U
RATI GS
Supply Voltage (V
CC
) ................................................. 6V
V
+ ...........................................................................................
12V
V
– .......................................................................................
–12V
Input Voltage
Driver ........................................................... V
–
to V
+
Receiver ................................................. –30V to 30V
ON/OFF Pin .............................................. GND to 12V
Output Voltage
Driver ................................. (V
–
+ 30V) to (V
+
– 30V)
Receiver .................................. –0.3V to (V
CC
+ 0.3V)
PACKAGE/ORDER I FOR ATIO
TOP VIEW
NC
C1
+
V
+
C1
–
C2
+
C2
–
V
–
TR2 OUT
REC2 IN
1
2
3
4
5
6
7
8
9
LT1080
18 ON/OFF
17 V
CC
16 GND
15 TR1 OUT
14 REC1 IN
13 REC1 OUT
12 TR1 IN
11 TR2 IN
10 REC2 OUT
N PACKAGE
18-LEAD PDIP
ORDER PART
NUMBER
LT1080CJ
LT1080CN
LT1080CSW
LT1080IN
LT1080ISW
LT1080MJ
J PACKAGE
18-LEAD CERDIP
SW PACKAGE
18-LEAD PLASTIC SO WIDE
T
JMAX
= 150°C,
θ
JA
= 100°C/W,
θ
JC
= 40°C/W (J)
T
JMAX
= 150°C,
θ
JA
= 120°C/W,
θ
JC
= 50°C/W (N)
T
JMAX
= 150°C,
θ
JA
= 90°C/W,
θ
JC
= 26°C/W (SW)
2
U
U
W
W W
U
W
(Note 1)
Short-Circuit Duration
V
+ ......................................................................................
30 sec
V
– ......................................................................................
30 sec
Driver Output ............................................... Indefinite
Receiver Output ........................................... Indefinite
Operating Temperature Range
LT1080C/LT1081C ................................. 0°C to 70°C
LT1080I/LT1081I ................................ –40°C to 85°C
LT1080M/LT1081M .......................... –55°C to 125°C
Storage Temperature Range ..................–65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
TOP VIEW
C1
+
V
+
C1
–
C2
+
C2
–
V
–
TR2 OUT
REC2 IN
1
2
3
4
5
6
7
8
LT1081
16 V
CC
15 GND
14 TR1 OUT
13 REC1 IN
12 REC1 OUT
11 TR1 IN
10 TR2 IN
9
REC2 OUT
ORDER PART
NUMBER
LT1081CJ
LT1081CN
LT1081CSW
LT1081IN
LT1081ISW
LT1081MJ
J PACKAGE
16-LEAD CERDIP
N PACKAGE
16-LEAD PDIP
SW PACKAGE
16-LEAD PLASTIC SO WIDE
T
JMAX
= 150°C,
θ
JA
= 100°C/W,
θ
JC
= 40°C/W (J)
T
JMAX
= 150°C,
θ
JA
= 120°C/W,
θ
JC
= 50°C/W (N)
T
JMAX
= 150°C,
θ
JA
= 95°C/W,
θ
JC
= 27°C/W (SW)
LT1080/LT1081
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 2)
PARAMETER
Driver
Output Voltage Swing
Logic Input Voltage Level
Logic Input Current
Output Short-Circuit Current
Output Leakage Current
Data Rate (Note 6)
Slew Rate
Receiver
Input Voltage Thresholds
Input Low Threshold
Input High Threshold
Hysteresis
Input Resistance
Output Voltage
Output Short-Circuit Current
Output Leakage Current
Power Supply Generator (Note 4)
V
+
Output Voltage
I
OUT
= 0mA
I
OUT
= 10mA
I
OUT
= 15mA
I
OUT
= 0mA
I
OUT
= –10mA
I
OUT
= –15mA
q
ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
Positive
Negative
q
q
q
q
q
q
TYP
7.3
–6.5
1.4
1.4
5
5
MAX
UNITS
V
V
Load = 3k to GND Both Outputs
Input Low Level (V
OUT
= High)
Input High Level (V
OUT
= Low)
V
IN
≥
2V
V
IN
≤
0.8V
Sourcing Current, V
OUT
= 0V
Sinking Current, V
OUT
= 0V
SHUTDOWN (Note 3), V
OUT
=
±30V
R
L
= 3k, C
L
= 2500pF
R
L
= 3k, C
L
= 1000pF
R
L
= 3k, C
L
= 51pF
5
–5
2
0.8
20
20
V
V
µA
µA
mA
mA
9
–9
q
12
–12
10
100
µA
kBd
kBd
120
250
4
Commercial
Industrial and Military
Commercial
Industrial and Military
q
q
q
q
q
15
1.3
1.3
1.7
1.7
30
V/µs
V
V
0.8
0.2
2.4
3.0
1
7
0.4
V
V
V
kΩ
V
V
mA
mA
0.1
3
0.4
5
0.2
4.8
–20
1
1
V
IN
=
±10V
Output Low, I
OUT
= –1.6mA
Output High, I
OUT
= 160µA (V
CC
= 5V)
Sinking Current, V
OUT
= V
CC
Sourcing Current, V
OUT
= 0V
SHUTDOWN (Note 3), 0V
≤
V
OUT
≤
V
CC
q
q
q
3.5
–10
0.6
10
µA
V
V
V
V
V
V
8.0
7.0
6.5
–7.5
–5.5
–5.0
q
q
9.0
8.0
7.5
–8.5
–6.5
–6.0
12
1
22
100
80
1
V
–
Output Voltage
Supply Current
Supply Leakage Current (V
CC
)
ON/OFF Pin Current
Supply Rise Time
SHUTDOWN (Note 3), LT1080 Only
0V
≤
V
ON/OFF
≤
5V, LT1080 Only
(Note 5), LT1080 Only
mA
µA
µA
ms
–15
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
These parameters apply for 4.5V
≤
V
CC
≤
5.5V and V
ON/OFF
= 3V,
unless otherwise specified.
Note 3:
V
ON/OFF
= 0.4V for –55°C
≤
T
A
≤
50°C, and V
ON/OFF
= 0.2V for
50°C
≤
T
A
≤
125°C. (LT1080 only)
Note 4:
Unless otherwise specified, V
CC
= 5V, external loading of V
+
and
V
–
equals zero and the driver outputs are low (inputs high).
Note 5:
Time from either SHUTDOWN high or power on until V
+
≥
6V and
V
–
≤
–6V. All external capacitors are 1µF.
Note 6:
Data rate operation guaranteed by slew rate, short-circuit current
and propagation delay tests.
3
LT1080/LT1081
PI FU CTIO S
C1
+
; C1
–
; C2
+
; C2
–
(Pins 2, 4, 5, 6):
Requires an external
capacitor (≥1µF) from C1
+
to C1
–
and another from C2
+
to C2
–
. Pin 2 can be used for connecting a second positive
supply. When a separate positive supply is used, C1 can be
deleted.
V
+
(Pin 3):
Positive Supply for RS232 Drivers.
V
+
≈
2V
CC
– 1.5V. Requires an exterenal capacitor (≥1µF)
for charge storage. May be loaded (up to 15mA) for
external system use. Loading does reduce V
+
voltage (see
graphs). Capacitor may be tied to ground or +5V input
supply. With multiple transceivers, the V
+
and V
–
pins may
be paralleled into common capacitors.
V
–
(Pin 7):
Negative Supply for RS232 Drivers.
V
–
≈
–(2V
CC
– 2.5V). Requires an external capacitor
(≥1µF) for charge stroage. May be loaded (up to –15mA)
for external system use. Loading does reduce V
–
voltage
(see graphs). With multiple transceivers, the V
+
and V
–
pins may be paralleled into common capacitors.
TR2 OUT; TR1 OUT (Pins 8, 15):
Driver Outputs with
RS232 Voltage Levels. Outputs are in a high impedance
state when in the SHUTDOWN mode or when power is off
(V
CC
= 0V) to allow data line sharing. Outputs are fully
short-circuit protected from (V
–
+ 30V) to (V
+
– 30V) with
power on, off or in the SHUTDOWN mode. Typical output
breakdowns are greater than
±45V
and higher applied
TYPICAL PERFOR A CE CHARACTERISTICS
Driver Output Voltage
10
8
V
CC
= 5.5V
OUTPUT HIGH
10
8
DRIVER OUTPUT VOLTAGE (V)
6
4
2
0
–2
–4
–6
–8
4
2
0
–2
–4
–6
LOADED TO V
+
LOADED TO GROUND
V
CC
= 5V
SUPPLY VOLTAGE (V)
V
CC
= 5V
OUTPUT VOLTAGE (V)
V
CC
= 4.5V
R
L
= 3k
V
CC
= 5V
V
CC
= 4.5V
–10
–55
V
CC
= 5.5V
–25
OUTPUT LOW
0
25
50
75
TEMPERATURE (°C)
100
125
4
U W
U
U
U
(Pin numbers refer to LT1080)
voltages will not damage the device if moderately current
limited. Shorting one output will affect output from the
other.
REC2 IN; REC1 IN (Pins 9, 14):
Receiver Inputs. Accepts
RS232 voltage levels (±30V) and has 0.4V of hysteresis to
provide noise immunity. Input impedance is nominally
5kΩ.
REC2 OUT; REC1 OUT (Pins 10, 13):
Receiver Outputs
with TTL/CMOS Voltage Levels. Outputs are in a high
impedance state when in the SHUTDOWN mode to allow
data line sharing. Outputs are fully short-circuit protected
to ground or V
CC
with power on, off or in the SHUTDOWN
mode.
TR2 IN; TR1 IN (Pins 11, 12):
RS232 Driver Input Pins.
Inputs are TTL/CMOS compatible. Inputs should not be
allowed to float. Tie unused inputs to V
CC
.
GND (Pin 16):
Ground Pin.
V
CC
(Pin 17):
Input Supply Pin. Supply current drops to
zero in the SHUTDOWN mode.
ON/OFF (Pin 18):
Contols the operation mode of the
LT1080 and is TTL/CMOS compatible. A logic low puts the
device in the SHUTDOWN mode which reduces input
supply current to zero and places both driver and receiver
outputs in a high impedance state. A logic high fully
enables the device.
Supply Generator Outputs
V
+
OUTPUT VOLTAGE
LOADED TO V
–
LOADED TO GROUND
10
8
6
4
2
0
–2
–4
–6
–8
–10
Supply Generation from V
CC
or Shutdown
V
+
SUPPLY
V
CC
= 5V
C1 TO C4 = 1µF
R
L
= 4.7k; V
+
TO V
–
6
–8
–10
0
2
4
V
–
OUTPUT VOLTAGE
6 8 10 12 14 16 18 20
OUTPUT CURRENT (mA)
1080/81 G02
V
–
SUPPLY
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
TIME (ms)
1080/81 G03
1080/81 G01
LT1080/LT1081
TYPICAL PERFOR A CE CHARACTERISTICS
Receiver Input Thresholds
3.00
2.75
2.50
100
OUTPUT CURRENT (mA)
INPUT THRESHOLD (V)
INPUT CURRENT (µA)
2.25
2.00
1.75
1.50
1.25
1.00
0.75
0.50
–55
–25
0
25
50
75
TEMPERATURE (°C)
100
125
INPUT LOW
INPUT HIGH
ON/OFF Pin Thresholds
5.0
4.5
ON/OFF PIN VOLTAGE (V)
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
–55
MAXIMUM OFF VOLTAGE
MINIMUM ON VOLTAGE
OUTPUT LEAKAGE CURRENT (µA)
SUPPLY CURRENT (nA)
–25
0
25
50
75
TEMPERATURE (°C)
Output Waveforms
5V
0V
–5V
5V
0V
5V
0V
0
V
CC
= 5V
R
L
= 3k
2µs
4µs
6µs
8µs
1080/81 G10.tiff
DRIVER
OUTPUT
RECEIVER
OUTPUT
INPUT
U W
100
Receiver Output
Short-Circuit Current
40
35
OUTPUT SINKING
10
ON/OFF Pin Current vs Voltage
30
25
20
15
10
5
0
–5
OUTPUT SOURCING
1
0.1
–55
–10
–25
0
25
50
75
TEMPERATURE (°C)
100
125
0
1
2
3
INPUT VOLTAGE (V)
4
5
1080/81 G06
1080/81 G04
1080/81 G05
Supply Current in Shutdown
1000
V
CC
= 5V
100
Driver Output Leakage in
Shutdown
100
10
10
1
V
OUT
= 30V
V
OUT
= –30V
125
1
–55
–25
0
25
50
75
TEMPERATURE (°C)
100
125
0.1
–55
–25
0
25
50
75
TEMPERATURE (°C)
100
125
1080/81 G07
1080/81 G08
1080/81 G09
Shutdown to Driver Output
DRIVER 10V
OUTPUT 5V
HIGH 0V
RECEIVER 0V
OUTPUT –5V
LOW –10
ON/OFF
INPUT
5V
0V
0
V
CC
= 5V
R
L
= 3k
1ms
2ms
3ms
4ms
1080/81 G11.tiff
Shutdown to Receiver Output
6V
4V
2V
0V
5V
0V
0
V
CC
= 5V
1ms
2ms
3ms
4ms
1080/81 G11.tiff
RECEIVER
OUTPUT
ON/OFF
INPUT
5
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