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Электронный компонент: LT1281AI

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LT1280A/LT1281A
Low Power 5V RS232
Dual Driver/Receiver with
0.1
F Capacitors
R
Output Waveforms
LT1280A TA02
DRIVER
OUTPUT
R
L
= 3k
C
L
= 2500pF
RECEIVER
OUTPUT
C
L
= 50pF
INPUT
S
FEATURE
D
U
ESCRIPTIO
The LT
1280A/LT1281A are dual RS232 driver/receiver
pairs with integral charge pump to generate RS232 volt-
age levels from a single 5V supply. These circuits feature
rugged bipolar design to provide operating fault tolerance
and ESD protection unmatched by competing CMOS
designs. Using only 0.1
F external capacitors, these cir-
cuits consume only 40mW of power, and can operate to
120kbaud even while driving heavy capacitive loads. New
ESD structures on the chip allow the LT1280A/LT1281A to
survive multiple
10kV strikes, eliminating the need for
costly TransZorbs
on the RS232 line pins. The LT1280A/
LT1281A are fully compliant with EIA RS232 standards.
Driver outputs are protected from overload, and can be
shorted to ground or up to
30V without damage. During
shutdown or power-off conditions, driver and receiver
outputs are in a high impedance state, allowing line
sharing.
The LT1281A is available in 16-pin DIP and SO packages.
The LT1280A is supplied in 18-pin DIP and SO packages
for applications which require shutdown.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TransZorb is a registered trademark of General Instruments, GSI
s
Portable Computers
s
Battery-Powered Systems
s
Power Supply Generator
s
Terminals
s
Modems
U
S
A
O
PPLICATI
U
A
O
PPLICATI
TYPICAL
5k
5k
0.1
F
0.1
F
0.1
F
0.1
F
LOGIC
INPUTS
LOGIC
OUTPUTS
ON/OFF
18
10
13
11
12
6
5
4
2
16
9
14
8
15
7
3
17
5V INPUT
V
+
OUT
V
OUT
RS232 OUTPUT
RS232 OUTPUT
RS232 INPUT
RS232 INPUT
LT1280A TA01
LT1280A
+
+
+
+
s
10mA Max Supply Current
s
ESD Protection over
10kV
s
Uses Small Capacitors: 0.1
F
s
120kBaud Operation for R
L
= 3k, C
L
= 2500pF
s
250kBaud Operation for R
L
= 3k, C
L
= 1000pF
s
Outputs Withstand
30V Without Damage
s
CMOS Comparable Low Power: 40mW
s
Operates from a Single 5V Supply
s
Rugged Bipolar Design
s
Outputs Assume a High Impedance State When Off
or Powered Down
s
Meets All RS232 Specifications
s
Available With or Without Shutdown
s
Absolutely No Latch-up
s
Available in SO Package
2
LT1280A/LT1281A
A
U
G
W
A
W
U
W
A
R
BSOLUTE
XI
TI
S
Supply Voltage (V
CC
) ................................................ 6V
V
+
........................................................................ 13.2V
V
...................................................................... 13.2V
Input Voltage
Driver ........................................................... V
to V
+
Receiver ............................................... 30V to 30V
ON/OFF ................................................. 0.3V to 12V
Output Voltage
Driver ...................................... V
+
30V to V
+ 30V
Receiver .................................... 0.3V to V
CC
+ 0.3V
Short-Circuit Duration
V
+
................................................................... 30 sec
V
................................................................... 30 sec
Driver Output .............................................. Indefinite
Receiver Output .......................................... Indefinite
Operating Temperature Range
LT1280AC/LT1281AC ............................. 0
C to 70
C
LT1280AI/LT1281AI .......................... 40
C to 85
C
Storage Temperature Range ................ 65
C to 150
C
Lead Temperature (Soldering, 10 sec)................. 300
C
W
U
U
PACKAGE/ORDER I FOR ATIO
ORDER PART
NUMBER
ORDER PART
NUMBER
(Note 2)
ELECTRICAL C
C
HARA TERISTICS
Consult factory for Military grade parts.
1
2
3
4
5
6
7
8
9
TOP VIEW
18
17
16
15
14
13
12
11
10
NC
C1
+
V
+
C1
C2
+
C2
V
TR2 OUT
REC2 IN
N PACKAGE 18-LEAD PDIP
SW PACKAGE
18-LEAD PLASTIC SO WIDE
ON/OFF
V
CC
GND
TR1 OUT
REC1 IN
REC1 OUT
TR1 IN
TR2 IN
REC2 OUT
T
JMAX
= 125
C,
JA
= 80
C/ W,
JC
= 36
C/W (N)
T
JMAX
= 125
C,
JA
= 90
C/ W,
JC
= 26
C/W (SW)
LT1280ACN
LT1280AIN
LT1280ACSW
LT1280AISW
1
2
3
4
5
6
7
8
TOP VIEW
16
15
14
13
12
11
10
9
C1
+
V
+
C1
C2
+
C2
V
TR2 OUT
REC2 IN
V
CC
GND
TR1 OUT
REC1 IN
REC1 OUT
TR1 IN
TR2 IN
REC2 OUT
N PACKAGE 16-LEAD PDIP
SW PACKAGE
16-LEAD PLASTIC SO WIDE
T
JMAX
= 125
C,
JA
= 90
C/ W,
JC
= 46
C/W (N)
T
JMAX
= 125
C,
JA
= 95
C/ W,
JC
= 27
C/W (SW)
LT1281ACN
LT1281AIN
LT1281ACSW
LT1281AISW
(Note 1)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Power Supply Generator
V
+
Output
7.9
V
V
Output
7.0
V
Supply Current (V
CC
)
(Note 3), T
A
= 25
C
8
10
mA
q
14
mA
Supply Current When OFF (V
CC
)
Shutdown (Note 4) LT1280A Only
q
1
10
A
Supply Rise Time
C1 = C2 = C3 = C4 = 0.1
F
0.2
ms
Shutdown to Turn-On
LT1280A Only
0.2
ms
ON/OFF Pin Thresholds
Input Low Level (Device Shutdown)
q
0.8
1.2
V
Input High Level (Device Enabled)
q
1.6
2.4
V
ON/OFF Pin Current
0V
V
ON/OFF
5V
q
15
80
A
Oscillator Frequency
130
kHz
Driver
Output Voltage Swing
Load = 3k to GND
Positive
q
5.0
7.5
V
Negative
q
6.3
5.0
V
Logic Input Voltage Level
Input Low Level (V
OUT
= High)
q
1.4
0.8
V
Input High Level (V
OUT
= Low)
q
2.0
1.4
V
3
LT1280A/LT1281A
Driver Output Voltage
TEMPERATURE (C)
55
10
DRIVER OUTPUT VOLTAGE (V)
8
4
2
0
10
4
0
50
75
LT1280A TPC03
6
6
8
2
25
25
100
125
OUTPUT HIGH
OUTPUT LOW
R
L
= 3k
V
CC
= 5V
V
CC
= 4.5V
V
CC
= 5.5V
V
CC
= 4.5V
V
CC
= 5V
V
CC
= 5.5V
C
C
HARA TERISTICS
U
W
A
TYPICAL PERFOR
CE
ELECTRICAL C
C
HARA TERISTICS
(Note 2)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Logic Input Current
0.8V
V
IN
2.0V
q
5
20
A
Output Short-Circuit Current
V
OUT
= 0V
9
17
mA
Output Leakage Current
Shutdown V
OUT
=
30V (Note 4)
q
10
100
A
Data Rate (Note 7)
R
L
= 3k, C
L
= 2500pF
120
kBaud
R
L
= 3k, C
L
= 1000pF
250
kBaud
Slew Rate
R
L
= 3k, C
L
= 51pF
15
30
V/
s
R
L
= 3k, C
L
= 2500pF
4
7
V/
s
Propagation Delay
Output Transition t
HL
High-to-Low (Note 5)
0.6
1.3
s
Output Transition t
LH
Low-to-High
0.5
1.3
s
Receiver
Input Voltage Thresholds
Input Low Threshold (V
OUT
= High)
C Grade
q
0.8
1.3
V
Input High Threshold (V
OUT
= Low)
C Grade
q
1.7
2.4
V
Input Low
I Grade
q
0.2
1.3
V
Input High
I Grade
q
1.7
3.0
V
Hysteresis
q
0.1
0.4
1.0
V
Input Resistance
V
IN
=
10V
3
5
7
k
Output Leakage Current
Shutdown (Note 4) 0
V
OUT
V
CC
q
1
10
A
Output Voltage
Output Low, I
OUT
= 1.6mA
q
0.2
0.4
V
Output High, I
OUT
= 160
A (V
CC
= 5V)
q
3.5
4.2
V
Output Short-Circuit Current
Sinking Current, V
OUT
= V
CC
20
10
mA
Sourcing Current, V
OUT
= 0V
10
20
mA
Propagation Delay
Output Transition t
HL
High-to-Low (Note 6)
250
600
ns
Output Transition t
LH
Low-to-High
350
600
ns
Note 4: Supply current measurements in shutdown are performed with
V
ON/OFF
0.1V.
Note 5: For driver delay measurements, R
L
= 3k and C
L
= 51pF. Trigger
points are set between the driver's input logic threshold and the output
transition to the zero crossing (t
HL
= 1.4V to 0V and t
LH
= 1.4V to 0V).
Note 6: For receiver delay measurements, C
L
= 51pF. Trigger points are
set between the receiver's input logic threshold and the output transition
to standard TTL/CMOS logic threshold (t
HL
= 1.3V to 2.4V and t
LH
= 1.7V
to 0.8V).
Note 7: Data rate operation guaranteed by slew rate, short-circuit current
and propagation delay tests.
The
q
denotes specifications which apply over the operating temperature
range (0
C
T
A
70
C for commercial grade, and 40
C
T
A
85
C for
industrial grade.
Note 1: Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
Note 2: Testing done at V
CC
= 5V and V
ON/OFF
= 3V, unless otherwise
specified.
Note 3: Supply current is measured as the average over several charge
pump cycles. C
+
= C
= C1 = C2 = 0.1
F. All outputs are open, with all
driver inputs tied high.
Driver Maximum Output Voltage
vs Load Capacitance
LOAD CAPACITANCE (nF)
0
5.0
PEAK OUTPUT VOLTAGE (V)
5.5
6.0
6.5
7.0
7.5
8.0
2
4
6
8
LT1280A TPC01
10
1
3
5
7
9
20k BAUD
60k BAUD
120k BAUD
Driver Minimum Output Voltage
vs Load Capacitance
LOAD CAPACITANCE (nF)
0
7.0
PEAK OUTPUT VOLTAGE (V)
6.5
6.0
5.5
5.0
4.5
4.0
2
4
6
8
LT1280A TPC02
10
1
3
5
7
9
120k BAUD
60k BAUD
20k BAUD
4
LT1280A/LT1281A
C
C
HARA TERISTICS
U
W
A
TYPICAL PERFOR
CE
Receiver Input Thresholds
Driver Leakage in Shutdown
ON/OFF Thresholds
Receiver Short-Circuit Current
Slew Rate vs Load Capacitance
TEMPERATURE (C)
55
0.50
THRESHOLD VOLTAGE (V)
0.75
1.25
1.50
1.75
3.00
2.25
0
50
75
LT1280A TPC04
1.00
2.50
2.75
2.00
25
25
100
125
INPUT HIGH
INPUT LOW
DATA RATE (kBAUD)
0
0
SUPPLY CURRENT (mA)
10
20
30
40
50
25
50
75
100
LT1280A TPC05
125
150
2 DRIVERS ACTIVE
R
L
= 3k
C
L
= 2500pF
Supply Current vs Data Rate
TEMPERATURE (C)
55
THRESHOLD VOLTAGE (V)
2.0
2.5
3.0
25
75
LT1280A TPC06
1.5
1.0
25
0
50
100
125
0.5
0
ON THRESHOLD
OFF THRESHOLD
Supply Current
TEMPERATURE (C)
55
0
SUPPLY CURRENT (mA)
10
25
0
50
75
LT1280A TPC07
5
20
15
25
25
100
125
2 DRIVERS LOADED R
L
= 3k
1 DRIVER LOADED R
L
= 3k
NO LOAD
Driver Short-Circuit Current
LOAD CAPACITANCE (nF)
0
SLEW RATE (V/s)
12
16
4.0
LT1280A TPC11
8
4
0
1.0
2.0
3.0
5.0
10
14
6
2
3.5
0.5
1.5
2.5
4.5
+SLEW
SLEW
TEMPERATURE (C)
0.1
LEAKAGE CURRENT (
A)
10
100
LT1280A TPC08
1
55
0
50
75
25
25
100
125
V
OUT
= 30V
V
OUT
= 30V
TEMPERATURE (
C)
55
SHORT-CIRCUIT CURRENT (mA)
20
25
30
25
75
LT1280A TPC09
15
10
25
0
50
100
125
5
0
I
SC
+
I
SC
TEMPERATURE (
C)
55
0
SHORT-CIRCUIT CURRENT (mA)
20
50
0
50
75
LT1280A TPC10
10
40
30
25
25
100
125
RX I
SC
RX I
SC
+
5
LT1280A/LT1281A
C
C
HARA TERISTICS
U
W
A
TYPICAL PERFOR
CE
Shutdown to Driver Outputs
Driver Output Waveforms
LT1280A TPC13
LT1280A TPC12
PI FU CTIO S
U
U
U
Output current capability is sufficient for load conditions
up to 2500pF. Outputs are in a high impedance state when
in shutdown mode or V
CC
= 0V. Outputs are fully short-
circuit protected from V
+ 30V to V
+
30V. Applying
higher voltages will not damage the device if the overdrive
is moderately current limited. Short circuits on one
output can load the power supply generator and may
disrupt the signal levels of the other outputs. The driver
outputs are protected against ESD to
10kV for human
body model discharges.
REC1 IN, REC2 IN: Receiver Inputs. These pins accept
RS232 level signals (
30V) into a protected 5k terminat-
ing resistor. The receiver inputs are protected against ESD
to
10kV for human body model discharges. Each receiver
provides 0.4V of hysteresis for noise immunity. Open
receiver inputs assume a logic low state.
REC1 OUT, REC2 OUT: Receiver outputs with TTL/CMOS
Voltage Levels. Outputs are in a high impedance state
when in shutdown mode to allow data line sharing. Out-
puts are fully short-circuit protected to ground or V
CC
with
the power ON, OFF or in the shutdown mode.
C1
+
, C1
, C2
+
, C2
: Commutating Capacitor Inputs.
These pins require two external capacitors C
0.1
F: one
from C1
+
to C1
and another from C2
+
to C2
. C1 should
be deleted if a separate 12V supply is available and
connected to pin C1
+
. Similarly, C2 should be deleted if a
separate 12V supply is connected to pin V
.
INPUT
DRIVER OUTPUT
R
L
= 3k
DRIVER OUTPUT
R
L
= 3k
C
L
= 2500pF
10V
5V
GND
DRIVER 1
OUTPUT
DRIVER 2
OUTPUT
ON/OFF PIN
GND
10V
5V
V
CC
: 5V Input Supply Pin. This pin should be decoupled
with a 0.1
F ceramic capacitor close to the package pin.
Insufficient supply bypassing can result in low output
drive levels and erratic charge pump operation.
GND: Ground Pin.
ON/OFF: A TTL/CMOS Compatible Operating Mode Con-
trol. A logic low puts the LT1280A in shutdown mode.
Supply current drops to zero and both driver and receiver
outputs assume a high impedance state. A logic high fully
enables the device.
V
+
: Positive Supply Output (RS232 Drivers). V
+
2V
CC
1.5V. This pin requires an external charge storage capaci-
tor C
0.1
F, tied to ground or V
CC
. Larger value capaci-
tors may be used to reduce supply ripple. With multiple
transceivers, the V
+
and V
pins may be paralleled into
common capacitors.
V
: Negative Supply Output (RS232 Drivers). V
(2V
CC
2.5V). This pin requires an external charge storage
capacitor C
0.1
F. Larger value capacitors may be used
to reduce supply ripple. With multiple transceivers, the V
+
and V
pins may be paralleled into common capacitors.
TR1 IN, TR2 IN: RS232 Driver Input Pins. These inputs are
TTL/CMOS compatible. Inputs should not be allowed to
float. Tie unused inputs to V
CC
.
TR1 OUT, TR2 OUT: Driver Outputs at RS232 Voltage
Levels. Driver output swing meets RS232 levels for loads
up to 3k. Slew rates are controlled for lightly loaded lines.