LTC1384
5V Low Power RS232
Transceiver with 2 Receivers
Active in Shutdown
FEATURES
■
■
DESCRIPTIO
■
■
■
■
■
■
Operates from a Single 5V Supply
Low Supply Current: I
CC
= 220µA
I
CC
= 35µA in Shutdown Mode with Both
Receivers Kept Alive
ESD Protection Over
±10kV
Uses Small Capacitors: 0.1µF
Operates to 120kBaud
Output Overvoltage Does Not Force Current
Back into Supplies
RS232 I/O Lines Can Be Forced to
±25V
Without Damage
Pin Compatible with LT1180A
The LTC
®
1384 is an ultra-low power 2-driver/2-receiver
RS232 transceiver that operates from a single 5V
supply. The charge pump requires only four space-
saving 0.1µF capacitors.
The transceiver operates in one of two modes, Normal and
Shutdown. In the Normal mode, I
CC
is only 220µA with the
driver outputs unloaded. In the Shutdown mode, the
charge pump is turned off, the driver outputs are forced
into three-state, both receivers are kept active and I
CC
drops to 35µA. The receiver outputs may be forced into
three-state at any time using the receiver enable (RX EN)
pin.
The LTC1384 is fully compliant with all data rate and
overvoltage RS232 specifications. The transceiver can
operate up to 120kbaud with a 2500pF, 3kΩ load. Both
driver outputs and receiver inputs can be forced to
±25V
without damage and can survive multiple
±10kV
ESD strikes.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
■
■
Notebook Computers
Palmtop Computers
TYPICAL APPLICATIO
2
0.1µF
4
5
0.1µF
6
12
V
CC
300k
LOGIC INPUT
LOGIC OUTPUT
11
13
5k
10
18
5k
LTC1384
V
CC
300k
2-Drivers/2-Receivers with Shutdown
and Receiver Enable
17
3
7
0.1µF
QUIESCENT CURRENT (µA)
Quiescent and Shutdown Supply Current
vs Temperature
1200
60
TEST CONDITION: V
CC
= 5V
1000
0.1µF
V
CC
= 5V
800
600
400
200
0
–20
LOGIC INPUT
15
232 OUTPUT
8
14
232 OUTPUT
232 INPUT
0
LOGIC OUTPUT
ON/OFF
9
16
232 INPUT
1
RX EN
LTC1384 • TA01
U
50
SHUTDOWN CURRENT (µA)
U
U
SHUTDOWN
CURRENT
40
30
QUIESCENT
CURRENT
20
10
0
20
40
TEMPERATURE (°C)
60
80
LTC1384 • TA02
1384fa
1
LTC1384
ABSOLUTE
AXI U
RATI GS
Short-Circuit Duration
V
+
................................................................... 30 sec
V
–
................................................................... 30 sec
Driver Output .............................................. Indefinite
Receiver Output .......................................... Indefinite
Operating Temperature Range
LTC1384C ............................................... 0°C to 70°C
LTC1384I ............................................ – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
Supply Voltage (V
CC
) ................................................ 6V
Input Voltage
Driver ....................................... – 0.3V to V
CC
+ 0.3V
Receiver ............................................... – 25V to 25V
Digital Input ............................... – 0.3V to V
CC
+ 0.3V
Output Voltage
Driver .................................................... – 25V to 25V
Receiver .................................... – 0.3V to V
CC
+ 0.3V
PACKAGE/ORDER I FOR ATIO
TOP VIEW
RX EN
C1
+
V
+
1
2
3
4
5
6
7
8
9
20 ON/OFF
19 VCC
18 GND
17 TR1 OUT
16 RX1 IN
15 RX1 OUT
14 TR1 IN
13 TR2 IN
12 RX2 OUT
11 NC
G PACKAGE
20-LEAD SSOP
ORDER PART
NUMBER
LTC1384CG
LTC1384IG
C1
–
C2
+
C2
–
V
–
TR2 OUT
RX2 IN
NC 10
T
JMAX
= 125°C,
θ
JA
= 135°C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
DC ELECTRICAL CHARACTERISTICS
PARAMETER
Any Driver
Output Voltage Swing
Logic Input Voltage Level
Logic Input Current
Output Short-Circuit Current
Output Leakage Current
Any Receiver
Input Voltage Thresholds
Hysteresis
Input Resistance
Output Voltage
CONDITIONS
3k to GND
The
●
denotes specifications which apply over the full operating
temperature range. V
CC
= 5V, C1 = C2 = C3 = C4 = 0.1µF, V
ON/OFF
= V
CC
, RX EN = 0V, unless otherwise noted.
MIN
Positive
Negative
●
●
●
●
●
●
Input Low Level (V
OUT
= High)
Input High Level (V
OUT
= Low)
V
IN
= V
CC
V
IN
= 0V
V
OUT
= 0V
Shutdown or V
CC
= 0V (Note 3), V
OUT
=
±10V
Input Low Threshold
Input High Threshold
– 10V
≤
V
IN
≤
10V
Output Low, I
OUT
= – 1.6mA (V
CC
= 5V)
Output High, I
OUT
= 160µA (V
CC
= 5V)
2
U
U
W
W W
U
W
TOP VIEW
RX EN 1
C1
+
V
+
18 ON/OFF
17 V
CC
16 GND
15 TR1 OUT
14 RX1 IN
13 RX1 OUT
12 TR1 IN
11 TR2 IN
10 RX2 OUT
SW PACKAGE
18-LEAD PLASTIC SO
ORDER PART
NUMBER
LTC1384CN
LTC1384CSW
LTC1384IN
LTC1384ISW
2
3
C1– 4
C2
+
5
C2– 6
V– 7
TR2 OUT 8
RX2 IN 9
N PACKAGE
18-LEAD PDIP
T
JMAX
= 125°C,
θ
JA
= 65°C/W
T
JMAX
= 125°C,
θ
JA
= 85°C/W
TYP
7.0
– 6.5
1.4
1.4
– 20
±12
±10
1.3
1.7
0.4
5
0.2
3.2
MAX
UNITS
V
V
V
V
µA
µA
mA
µA
V
V
V
kΩ
V
V
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5.0
– 5.0
2.0
0.8
5
– 40
±500
±9
●
●
●
●
●
●
0.8
0.1
3
3.0
2.4
1
7
0.4
LTC1384
DC ELECTRICAL CHARACTERISTICS
PARAMETER
Output Short-Circuit Current
Output Leakage Current
Power Supply Generator
V
+
Output Voltage
V
–
Output Voltage
Supply Rise Time
Power Supply
V
CC
Supply Current
Supply Leakage Current (V
CC
)
Digital Input Threshold Low
Digital Input Threshold High
The
●
denotes specifications which apply over the full operating
temperature range. V
CC
= 5V, C1 = C2 = C3 = C4 = 0.1µF, V
ON/OFF
= V
CC
, RX EN = 0V, unless otherwise noted.
CONDITIONS
Sinking Current, V
OUT
= V
CC
Sourcing Current, V
OUT
= 0V
EN = V
CC
, 0V
≤
V
OUT
≤
V
CC
I
OUT
= 0mA
I
OUT
= 8mA
I
OUT
= 0mA
I
OUT
= – 8mA
Shutdown to Turn-On
No Load (Note 2), 0°C to 70°C
No Load (Note 2), –40°C to 85°C
Shutdown (Note 3)
●
●
●
●
●
MIN
– 15
10
●
TYP
– 40
20
1
8.0
7.5
– 8.0
– 7.0
0.2
0.22
0.35
35
1.4
1.4
MAX
10
UNITS
mA
mA
µA
V
V
V
V
ms
0.5
1.0
50
0.8
2.0
mA
mA
µA
V
V
AC CHARACTERISTICS
PARAMETER
Slew Rate
Driver Propagation Delay
(TTL to RS232)
Receiver Propagation Delay
(RS232 to TTL)
The
●
denotes specifications which apply over the full operating temperature range.
V
CC
= 5V, C1 = C2 = C3 = C4 = 0.1µF,unless otherwise noted.
CONDITIONS
R
L
= 3k, C
L
= 51pF
R
L
= 3k, C
L
= 2500pF
t
HLD
(Figure 1)
t
LHD
(Figure 1)
t
HLR
(Figure 2)
t
LHR
(Figure 2)
MIN
3
●
●
●
●
TYP
8
5
2
2
0.3
0.3
MAX
30
3.5
3.5
0.8
0.8
UNITS
V/µs
V/µs
µs
µs
µs
µs
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
Note 2:
Supply current is measured with driver and receiver outputs
unloaded.
Note 3:
Measurements made in the Shutdown mode are performed
with V
ON/OFF
= 0V.
TYPICAL PERFOR A CE CHARACTERISTICS
Driver Output Voltage
vs Temperature
10
8
DRIVER OUTPUT VOLTAGE (V)
R
L
= 3k
OUTPUT HIGH
V
CC
= 5V
V
CC
= 4.5V
SUPPLY CURRENT (mA)
6
4
2
0
–2
–4
–6
–8
0
10
THRESHOLD VOLTAGE (V)
OUTPUT LOW
V
CC
= 4.5V
V
CC
= 5V
20
30
40
50
TEMPERATURE (°C)
60
70
U W
Receiver Input Thresholds
vs Temperature
2.2
2.0
V
TH
1.8
1.6
1.4
1.2
5
1.0
0
10
40
30
50
20
TEMPERATURE (˚C)
60
70
0
V
TL
35
30
25
20
15
10
45
40
Supply Current vs Data Rate
V
CC
= 5V
R
L
= 3k
C
L
= 2500pF
2 DRIVERS ACTIVE
0
25
50
75
100 125
DATA RATE (kBAUD)
150
175
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LTC1384
TYPICAL PERFOR A CE CHARACTERISTICS
V
CC
Supply Current
vs Temperature
18
16
SHORT-CIRCUIT CURRENT (mA)
SUPPLY CURRENT (mA)
14
12
10
8
6
4
2
0
0
10
20
30
40
50
TEMPERATURE (°C)
60
70
1 DRIVER LOADED
R
L
= 3k
2 DRIVERS LOADED
R
L
= 3k
14
12
10
8
6
4
2
0
0
I
SC–
I
SC+
SHORT-CIRCUIT CURRENT (mA)
LTC1384 • TPC04
Driver Leakage in Shutdown
vs Temperature
45
40
LEAKAGE CURRENT (µA)
35
30
25
20
15
10
5
0
0
10
30
20
40
50
TEMPERATURE (°C)
60
70
V
OUT
= 20V
V
OUT
= –20V
LTC1384 • TPC07
4
U W
Driver Short-Circuit Current
vs Temperature
18
16
Receiver Short-Circuit Current
vs Temperature
50
40
I
SC–
30
20
I
SC+
10
10
20
30
40
50
TEMPERATURE (°C)
60
70
0
10
30
20
50
40
TEMPERATURE (°C)
60
70
LTC1384 • TPC05
LTC1384 • TPC06
Driver Output Waveforms
DRIVER
OUTPUT
R
L
= 3k
C
L
= 2500pF
DRIVER
OUTPUT
R
L
= 3k
INPUT
Receiver Output Waveforms
RECEIVER
OUTPUT
C
L
= 51pF
INPUT
LTC1384 • TPC08
LTC1384 • TPC09
5µs/DIV
5µs/DIV
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LTC1384
PI FU CTIO S
V
CC
:
5V Input Supply Pin. This pin should be decoupled
with a 0.1µF ceramic capacitor.
GND:
Ground Pin.
ON/OFF:
TTL/CMOS Compatible Shutdown Pin. A logic
low puts the device in the Shutdown mode independent of
the RX EN pin. The supply current of the device drops to
35µA (two receivers alive) and both driver outputs are
forced into three-state.
RX EN:
TTL/CMOS Compatible Receiver Enable Pin. A
logic high forces the receiver outputs into three-state. A
logic low enables the receiver outputs.
V
+
:
Positive Supply Output (RS232 Drivers). V
+
≅
2V
CC
–
2V. This pin requires an external capacitor C = 0.1µF for
charge storage. The capacitor may be tied to ground or
V
CC
. With multiple devices, the V
+
and V
–
pins may share
a common capacitor. For large numbers of devices, in-
creasing the size of the shared common storage capaci-
tors is recommended to reduce ripple.
V
–
:
Negative Supply Output (RS232 Drivers). V
–
≅
– (2V
CC
– 2V). This pin requires an external capacitor C = 0.1µF for
charge storage.
C1
+
, C1
–
, C2
+
, C2
–
:
Commutating Capacitor Inputs. These
pins require two external capacitors C = 0.1µF: one from
C1
+
to C1
–
and another from C2
+
to C2
–
. To maintain
charge pump efficiency, the capacitor’s effective series
resistance should be less than 2Ω.
TR IN:
RS232 Driver Input Pins. Inputs are TTL/CMOS
compatible. The inputs of unused drivers can be left
unconnected since 300k input pull-up resistors to V
CC
are
included on chip. To minimize power consumption, the
internal driver pull-up resistors are disconnected from V
CC
in the Shutdown mode.
TR OUT:
Driver Outputs at RS232 Voltage Levels. Outputs
are in a high impedance state when in the Shutdown or V
CC
= 0V. The driver outputs are protected against ESD to
±10kV
for human body model discharges.
RX IN:
Receiver Inputs. These pins can be forced to
±25V
without damage. The receiver inputs are protected against
ESD to
±10kV
for human body model discharges. Each
receiver provides 0.4V of hysteresis for noise immunity.
RX OUT:
Receiver Outputs with TTL/CMOS Voltage Lev-
els. A logic high at RX EN puts the outputs into three-state.
SWITCHI G TI E WAVEFOR S
DRIVER
INPUT
DRIVER
OUTPUT
t
LHD
V
CC
1.4V
1.4V
0V
V
+
0V
t
HLD
LTC1384 • F01
Figure 1. Driver Propagation Delay Timing
W
W
U
U
U
U
RX
INPUT
RX
OUTPUT
t
LHR
1.7V
V
CC
1.3V
0V
2.4V
0.8V
t
HLR
V
CC
0V
LTC1384 • F02
0V
V
–
Figure 2. Receiver Propagation Delay Timing
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