LTC1338
5V Low Power RS232
5-Driver/3-Receiver Transceiver
FEATURES
s
s
s
s
s
s
s
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DESCRIPTIO
s
s
Low Supply Current: 500µA
0.2µA Supply Current in SHUTDOWN
50µA Supply Current in RECEIVER ALIVE Mode
ESD Protection Over
±10kV
Operates from a Single 5V Supply
Uses Small Capacitors: 0.1µF
Operates to 120k Baud
Three-State Outputs Are High Impedance When Off
Output Overvoltage Does Not Force Current
Back into Supplies
RS232 I/O Lines Can Be Forced to
±25V
Without Damage
Flowthrough Architecture
The LTC1338 is a 5-driver/ 3-receiver RS232 trans-
ceiver with very low supply current. In the no load
condition, the supply current is only 500µA. The charge
pump only requires four 0.1µF capacitors.
In SHUTDOWN mode, the supply current is further
reduced to 0.2µA. In RECEIVER ALIVE mode, all three
receivers are kept alive and the supply current is 50µA.
All RS232 outputs assume a high impedance state in
SHUTDOWN and with the power off.
The LTC1338 is fully compliant with all data rate and
overvoltage RS232 specifications. The transceiver can
operate up to 120k baud 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.
APPLICATI
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s
s
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S
Battery-Powered Modems
Battery-Powered DCE
Notebook Computers
Palmtop Computers
TYPICAL APPLICATI
V
+
C1
0.1µF
C2
0.1µF
DRIVER 1 OUT
DRIVER 2 OUT
RX1 IN
DRIVER 3 OUT
RX2 IN
DRIVER 4 OUT
RX3 IN
DRIVER 5 OUT
RX ENABLE
NC
V
CC
1
2
3
4
5
6
7
8
9
10
11
12
13
14
5-Drivers/3-Receivers with SHUTDOWN
28
LTC1338
27
26
25
24
23
22
21
20
19
18
17
16
15
C3
0.1µF
DRIVER 1 IN
DRIVER 2 IN
RX1 OUT
DRIVER 3 IN
RX2 OUT
DRIVER 4 IN
RX3 OUT
DRIVER 5 IN
GND
DRIVER ENABLE
NC
LTC1338 • TA01
V
–
C4
0.1µF
1200
1000
QUIESCENT CURRENT (µA)
800
600
400
200
0
–40
SHUTDOWN
CURRENT
QUIESCENT
CURRENT
–20
TEST CONDITION:
V
CC
= 5V, ALL DRIVER INPUTS TIED TO V
CC
.
U
Supply Current
1.2
1.0
SHUTDOWN CURRENT (µA)
UO
UO
0.8
0.6
0.4
0.2
0
100
0
20
40
60
TEMPERATURE (°C)
80
LTC1338 • TA02
1
LTC1338
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
V
+
1
V
CC
2
C1
+
3
C1
–
4
DR1 OUT 5
DR2 OUT 6
RX1 IN 7
DR3 OUT 8
RX2 IN 9
DR4 OUT 10
RX3 IN 11
DR5 OUT 12
RX ENABLE 13
NC 14
28 V
–
27 C2
+
26 C2
–
25 DR1 IN
24 DR2 IN
23 RX1 OUT
22 DR3 IN
21 RX2 OUT
20 DR4 IN
19 RX3 OUT
18 DR5 IN
17 GND
16 DR ENABLE
15 NC
Supply Voltage (V
CC
) ................................................ 6V
Input Voltage
Driver ....................................... – 0.3V to V
CC
+ 0.3V
Receiver ............................................... – 25V to 25V
Driver/Receiver Enable Pin ........ – 0.3V to V
CC
+ 0.3V
Output Voltage
Driver .................................................... – 25V to 25V
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
Commercial (LTC1338C) ........................ 0°C to 70°C
Industrial (LTC1338I) ........................ – 40°C to 85°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
ORDER PART
NUMBER
LTC1338CG
LTC1338CN
LTC1338CS
LTC1338IG
LTC1338IN
LTC1338IS
N PACKAGE
G PACKAGE
28-LEAD PLASTIC DIP
28-LEAD SSOP
S PACKAGE
28-LEAD PLASTIC SOL
T
JMAX
= 125°C,
θ
JA
= 96°C/W (G)
T
JMAX
= 125°C,
θ
JA
= 56°C/W (N)
T
JMAX
= 125°C,
θ
JA
= 85°C/W (S)
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
Output Short-Circuit Current
Output Leakage Current
Power Supply Generator
V
+
Output Voltage
V
–
Output Voltage
Supply Rise Time
CONDITIONS
3k to GND
V
CC
= 5V, C1 = C2 = C3 = C4 = 0.1µF, unless otherwise noted.
MIN
Positive
Negative
q
q
q
q
q
q
q
q
q
TYP
7.0
– 6.5
1.4
1.4
±12
±10
MAX
UNITS
V
V
V
V
µA
mA
µA
V
V
V
kΩ
V
V
mA
µA
V
V
V
V
ms
5.0
– 5.0
2.0
Input Low Level (V
OUT
= High)
Input High Level (V
OUT
= Low)
0
≤
V
IN
≤
V
CC
V
OUT
= 0V
SHUTDOWN, V
OUT
=
±20V
(Note 3)
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)
Sinking Current, V
OUT
= V
CC
SHUTDOWN, 0
≤
V
OUT
≤
V
CC
(Note 3)
I
OUT
= 0mA
I
OUT
= 12mA
I
OUT
= 0mA
I
OUT
= – 12mA
SHUTDOWN to Turn-On
0.8
±5
±500
0.8
0.1
3
3.5
– 15
q
q
q
1.3
1.7
0.4
5
0.2
4.8
– 40
1
8.0
7.5
– 8.0
– 7.0
0.2
2.4
1
7
0.4
10
2
U
W
U
U
W W
W
LTC1338
DC ELECTRICAL CHARACTERISTICS
V
CC
= 5V, C1 = C2 = C3 = C4 = 0.1µF, unless otherwise noted.
PARAMETER
Power Supply
V
CC
Supply Current
CONDITIONS
No Load (All Driver V
IN
= V
CC
)(Note 2) 0°C
≤
T
A
≤
70°C
No Load (All Driver V
IN
= 0V)(Note 2) 0°C
≤
T
A
≤
70°C
No Load (All Driver V
IN
= V
CC
)(Note 2) – 40°C
≤
T
A
≤
85°C
No Load (All Driver V
IN
= 0V)(Note 2) – 40°C
≤
T
A
≤
85°C
RECEIVER ALIVE Mode (Note 4)
SHUTDOWN (Note 3)
MIN
TYP
0.5
1.0
0.5
1.0
50
0.2
1.4
1.4
MAX
1.0
1.5
1.5
2.0
80
10
0.8
UNITS
mA
mA
mA
mA
µA
µA
V
V
q
q
q
q
Supply Leakage Current (V
CC
)
Driver/Receiver Enable Threshold Low
Driver/Receiver Enable Threshold High
2.0
AC CHARACTERISTICS
PARAMETER
Slew Rate
Driver Propagation Delay
(TTL to RS232)
Receiver Propagation Delay
(RS232 to TTL)
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
q
q
q
q
TYP
8
5
2
2
0.3
0.2
MAX
30
3.5
3.5
0.8
0.8
UNITS
V/µs
V/µs
µs
µs
µs
µs
The
q
denotes specifications which apply over the operating temperature
range of 0°C to 70°C or – 40°C to 85°C.
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. The V
DRIVER ENABLE
and V
RECEIVER ENABLE
= V
CC
.
Note 3:
Supply current and leakage current measurements in SHUTDOWN
are performed with V
DRIVER ENABLE
and V
RECEIVER ENABLE
= 0V.
Note 4:
Supply current measurement in RECEIVER ALIVE mode is
performed with V
DRIVER ENABLE
= 0V and V
RECEIVER ENABLE
= V
CC
.
TYPICAL PERFOR A CE CHARACTERISTICS
Driver Output Voltage
10
8
R
L
= 3k
OUTPUT HIGH
V
CC
= 5V
V
CC
= 4.5V
DRIVER OUTPUT VOLTAGE (V)
THRESHOLD VOLTAGE (V)
4
2
0
–2
–4
–6
–8
–40
–20
OUTPUT LOW
V
CC
= 4.5V
V
CC
= 5V
20
0
60
40
TEMPERATURE (°C)
80
100
SUPPLY CURRENT (mA)
6
LTC1338 • TPC01
U W
Receiver Input Thresholds
2.2
2.0
1.8
V
TH
1.6
1.4
1.2
1.0
–40 –20
60
50
40
30
20
10
0
Supply Current vs Data Rate
V
CC
= 5V
R
L
= 3k
C
L
= 2500pF
5 DRIVERS ACTIVE
V
TL
40
20
60
0
TEMPERATURE (˚C)
80
100
0
20
80
60
100
40
DATA RATE (k BAUD)
120
140
LTC1338 • TPC02
LTC1338 • TPC03
3
LTC1338
TYPICAL PERFOR A CE CHARACTERISTICS
V
CC
Supply Current
30
25
5 DRIVERS LOADED
R
L
= 3k
40
LEAKAGE CURRENT (µA)
SHORT-CIRCUIT CURRENT (mA)
SUPPLY CURRENT (mA)
20
15
10
5
0
–40 –20
1 DRIVER LOADED
R
L
= 3k
40
20
60
0
TEMPERATURE (°C)
LTC1338 • TPC04
Receiver Short-Circuit Current
60
SHORT-CIRCUIT CURRENT (mA)
50
40
I
SC–
30
I
SC+
20
LTC1338 • TPC08
LTC1338 • TPC09
10
–40 –20
40
20
60
0
TEMPERATURE (°C)
PI FU CTIO S
V
CC
:
5V Input Supply Pin. Supply current less than 0.2µA
in the SHUTDOWN mode. This pin should be decoupled
with a 0.1µF ceramic capacitor.
GND:
Ground Pin.
RECEIVER ENABLE:
TTL/CMOS Compatible Enable Pin.
Refer to Table 1 for its functional description. This pin can
not float.
DRIVER ENABLE:
TTL/CMOS Compatible Enable Pin. Re-
fer to Table 1 for its functional description. This pin can not
float.
V
+
:
Positive Supply Output (RS232 Drivers). V
+
≅
2V
CC
–
1V. This pin requires an external capacitor C = 0.1µF for
charge storage. The capacitor may be tied to ground or 5V.
With multiple devices, the V
+
and V
–
pins may be paral-
leled into common capacitors. For large numbers of
devices, increasing the size of the shared common storage
capacitors is recommended to reduce ripple.
V
–
:
Negative Supply Output (RS232 Drivers). V
–
≅
2V
CC
– 1.5V. 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 20Ω.
4
U W
80
100
Driver Leakage in Shutdown
50
20
18
16
14
12
10
8
6
4
0
–40 –20
40
20
0
60
TEMPERATURE (°C)
80
100
Driver Short-Circuit Current
V
OUT
= –20V
30
I
SC–
I
SC+
20
V
OUT
= 20V
10
0
–40
–20
20
0
60
40
TEMPERATURE (°C)
80
100
LTC1338 • TPC05
LTC1338 • TPC06
Driver Output Waveforms
DRIVER
OUTPUT
R
L
= 3k
C
L
= 2500pF
DRIVER
OUTPUT
R
L
= 3k
Receiver Output Waveforms
RECEIVER
OUTPUT
C
L
= 50pF
INPUT
INPUT
80
100
LTC1338 • TPC07
U
U
U
LTC1338
PI FU CTIO S
DRIVER IN:
RS232 Driver Input Pins. Inputs are TTL/
CMOS compatible. Inputs should not be allowed to float.
Tie unused inputs to V
CC
.
DRIVER OUT:
Driver Outputs at RS232 Voltage Levels.
Outputs are in a high impedance state when in SHUT-
DOWN, RECEIVER ALIVE mode or V
CC
= 0V. The driver
outputs are protected against ESD to
±10kV
for human
body model discharges.
Table 1. Functional Description
MODE
SHUTDOWN
Receiver Disable
RECEIVER ALIVE
Normal
RX ENABLE
0
0
1
1
DR ENABLE
0
1
0
1
DRIVERS
All driver outputs are
high impedance.
All drivers alive.
All driver outputs are
high impedance.
All drivers alive.
RECEIVERS
All receiver outputs are
high impedance.
All receiver outputs are
high impedance.
All receivers alive.
All receivers alive.
I
CC
(µA)(TYP)
0.2
500
50
500
SWITCHI G TI E WAVEFOR S
DRIVER
INPUT
DRIVER
OUTPUT
t
LHD
V
CC
1.4V
1.4V
0V
V
+
0V
t
HLD
LTC1338 • F01
Figure 1. Driver Propagation Delay Timing
W
W
U
U
U
U
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. Outputs are in a high impedance state when in SHUT-
DOWN or RECEIVER DISABLE mode to allow data line
sharing.
RX
INPUT
RX
OUTPUT
t
LHR
1.7V
V
CC
1.3V
0V
2.4V
0.8V
t
HLR
V
CC
0V
LTC1338 • F02
0V
V
–
Figure 2. Receiver Propagation Delay Timing
5
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