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Part Number LT1781

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1
LT1780/LT1781
Low Power 5V RS232
Dual Driver/Receiver with
±
15kV ESD Protection
TransZorb is a registered trademark of General Instruments, GSI.
R
Output Waveforms
1780/81 · TA02
DRIVER
OUTPUT
R
L
= 3k
C
L
= 2500pF
RECEIVER
OUTPUT
C
L
= 50pF
INPUT
0.1
µ
F
0.1
µ
F
0.1
µ
F
0.1
µ
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
1780/81 · TA01
5k
5k
LT1780
U
A
O
PPLICATI
TYPICAL
S
FEATURE
D
U
ESCRIPTIO
The LT
®
1780/LT1781 are dual RS232 driver/receiver pairs
with integral charge pump to generate RS232 voltage
levels from a single 5V supply. Using only 0.1
µ
F external
capacitors, these circuits consume only 40mW of power,
and can operate to 120kbaud even while driving heavy
capacitive loads. New ESD structures on the chip allow the
LT1780/LT1781 to survive
±
15kV air gap and
±
8kV con-
tact ESD tests per IEC 1000-4-2, eliminating the need for
costly TransZorbs
®
on the RS232 line pins. The LT1780/
LT1781 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 LT1780/LT1781 are direct upgrades to the LT1180A/
LT1181A, LT1280A/LT1281A and LT1381 for applications
which require the utmost ESD protection.
The LT1781 is available in 16-pin DIP,SO and SW pack-
ages. The LT1780 is supplied in 18-pin DIP and SW
packages for applications which require SHUTDOWN.
s
10mA Max Supply Current
s
ESD Protection to IEC 1000-4-2 Level 4
±
15kV Air Gap,
±
8kV Contact
s
Uses Small Capacitors: 0.1
µ
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
Portable Computers
s
Battery-Powered Systems
s
Power Supply Generator
s
Terminals
s
Modems
U
S
A
O
PPLICATI
, LTC and LT are registered trademarks of Linear Technology Corporation.
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2
LT1780/LT1781
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 ..................... 0
°
C to 70
°
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
LT1780CN
LT1780CSW
LT1781CN
LT1781CS
LT1781CSW
(Note 2)
ELECTRICAL C
C
HARA TERISTICS
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Power Supply Generator
V
+
Output
7.9
V
V
­
Output
­ 7
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) LT1780 Only
q
1
10
µ
A
Supply Rise Time
C1 = C2 = C3 = C4 = 0.1
µ
F
0.2
ms
SHUTDOWN to Turn-On
LT1780 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
µ
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
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
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 PLASTIC DIP
ON/OFF
V
CC
GND
TR1 OUT
REC1 IN
REC1 OUT
TR1 IN
TR2 IN
REC2 OUT
SW PACKAGE
18-LEAD PLASTIC SO
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)
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 PLASTIC DIP
S PACKAGE
16-LEAD PLASTIC SO
SW PACKAGE
16-LEAD PLASTIC SO
T
JMAX
= 125
°
C,
JA
= 90
°
C/ W,
JC
= 46
°
C/W (N)
T
JMAX
= 125
°
C,
JA
= 95
°
C/ W,
JC
= 34
°
C/W (S)
T
JMAX
= 125
°
C,
JA
= 95
°
C/ W,
JC
= 27
°
C/W (SW)
Consult factory for Industrial and Military grade parts.
(Note 1)
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3
LT1780/LT1781
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
µ
A
Output Short-Circuit Current
V
OUT
= 0V
±
7
17
mA
Output Leakage Current
SHUTDOWN V
OUT
=
±
30V (Note 4)
q
10
100
µ
A
Data Rate
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/
µ
s
R
L
= 3k, C
L
= 2500pF
4
7
V/
µ
s
Propagation Delay
Output Transition t
HL
High-to-Low (Note 5)
0.6
1.3
µ
s
Output Transition t
LH
Low-to-High
0.5
1.3
µ
s
Receiver
Input Voltage Thresholds
Input Low Threshold (V
OUT
= High)
0.8
1.3
V
Input High Threshold (V
OUT
= Low)
1.7
2.4
V
Hysteresis
q
0.1
0.4
1
V
Input Resistance
V
IN
=
±
10V
3
5
7
k
Output Leakage Current
SHUTDOWN (Note 4) 0
V
OUT
V
CC
q
1
10
µ
A
Output Voltage
Output Low, I
OUT
= ­ 1.6mA
q
0.2
0.4
V
Output High, I
OUT
= 160
µ
A (V
CC
= 5V)
q
3.5
4.2
V
Output Short-Circuit Current
Sinking Current, V
OUT
= V
CC
­ 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).
The
q
denotes specifications which apply over the operating temperature
range.
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
µ
F. All outputs are open, with all
driver inputs tied high.
­ 20
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4
LT1780/LT1781
C
C
HARA TERISTICS
U
W
A
TYPICAL PERFOR
CE
Receiver Input Thresholds
ON/OFF Thresholds
TEMPERATURE (
°
C)
­55
0.50
THRESHOLD VOLTAGE (V)
0.75
1.25
1.50
1.75
3.00
2.25
0
50
75
1780 · G04
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
1780 · G05
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
1780 · G06
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
1780 · G07
5
20
15
­25
25
100
125
2 DRIVERS LOADED R
L
= 3k
1 DRIVER LOADED R
L
= 3k
NO LOAD
Driver Output Voltage
Driver Minimum Output Voltage
vs Load Capacitance
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
1780 · G01
10
1
3
5
7
9
20k BAUD
60k BAUD
120k BAUD
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
1780 · G02
10
1
3
5
7
9
120k BAUD
60k BAUD
20k BAUD
TEMPERATURE (
°
C)
­55
­10
DRIVER OUTPUT VOLTAGE (V)
­8
­4
­2
0
10
4
0
50
75
1780 · G03
­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
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5
LT1780/LT1781
C
C
HARA TERISTICS
U
W
A
TYPICAL PERFOR
CE
Shutdown to Driver Outputs
Driver Output Waveforms
1780 · G13
1780 · G12
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
Driver Leakage in Shutdown
Receiver Short-Circuit Current
Slew Rate vs Load Capacitance
TEMPERATURE (
°
C)
0.1
LEAKAGE CURRENT
(
µ
A)
10
100
1780 · G08
1
­55
0
50
75
­25
25
100
125
V
OUT
= ­30V
V
OUT
= 30V
Driver Short-Circuit Current
TEMPERATURE (
°
C)
­55
SHORT-CIRCUIT CURRENT (mA)
20
25
30
25
75
1780 · G09
15
10
­25
0
50
100
125
5
0
ISC
+
ISC
­
TEMPERATURE (
°
C)
­55
0
SHORT-CIRCUIT CURRENT (mA)
20
50
0
50
75
1780 · G10
10
40
30
­25
25
100
125
RX ISC
­
RX ISC
+
LOAD CAPACITANCE (nF)
0
SLEW RATE (V/
µ
s)
12
16
4.0
1780 · G11
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