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
10801fe
LINER [ LINEAR TECHNOLOGY ]
