LT1342
5V RS232 Transceiver with
3V Logic Interface
FEATURES
s
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DESCRIPTIO
s
ESD Protection Over
±10kV
3V Logic Interface
Uses Small Capacitors: 0.1µF, 0.2µF
1µA Supply Current in Shutdown
Low Power Driver Disable Operating Mode
Pin Compatible with LT1137A
120kBaud Operation for R
L
= 3k, C
L
= 2500pF
250kBaud Operation for R
L
= 3k, C
L
= 1000pF
CMOS Comparable Low Power: 60mW
Operates from a 5V Supply and 3V Logic Supply
Easy PC Layout: Flowthrough Architecture
Rugged Bipolar Design
Outputs Assume a High Impedance State When
Off or Powered Down
Absolutely No Latchup
The LT
®
1342 is an advanced low power three-driver, five-
receiver RS232 transceiver. The LT1342 operates from a
5V supply and a 3V logic supply. Receiver outputs can
interface directly to 3V logic circuits. Included on the chip
is a shutdown pin for reducing supply current to near zero.
All receivers and drivers assume high impedance states
during shutdown.
The driver disable function provides additional control of
operating mode. When driver disable is high the charge
pump and drivers turn off. Receivers continue to operate
during driver disable.
New ESD structures on the chip allow the LT1342 to
survive multiple
±10kV
strikes, eliminating the need for
costly TransZorbs
®
on the RS232 line pins.
The LT1342 is fully compliant with all EIA RS232 specifi-
cations and operates in excess of 120kbaud even driving
heavy capacitive loads.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TransZorb is a registered trademark of General Instruments, GSI.
APPLICATI
s
s
S
Notebook Computers
Palmtop Computers
TYPICAL APPLICATI
V
+
0.1µF
2
×
0.1µF
DRIVER 1 OUT
RX1 IN
DRIVER 2 OUT
TO LINE
RX2 IN
RX3 IN
RX4 IN
DRIVER 3 OUT
RX5 IN
ON/OFF
3V V
L
5V V
CC
1
2
3
4
5
6
7
8
9
10
11
12
13
14
LT1342
28 V
–
27
26
25
24
23
22
21
20
19
18
17
16
15
DRIVER 1 IN
RX1 OUT
DRIVER 2 IN
RX2 OUT
RX3 OUT
RX4 OUT
DRIVER 3 IN
RX5 OUT
GND
DRIVER DISABLE
NC
LT1342 • TA01
0.1µF
2
×
0.1µF
RECEIVER
OUTPUT
V
L
= 3V
C
L
= 50pF
DRIVER
R
OUTPUT
R
L
= 3k
C
L
= 2500pF
TO 3V LOGIC
INPUT
U
Output Waveforms
LT1342 • TA02
UO
UO
1
LT1342
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
V
+
1
5V V
CC
2
C1
+
3
C1
–
4
DRIVER 1 OUT 5
RX1 IN 6
DRIVER 2 OUT 7
RX2 IN 8
RX3 IN 9
RX4 IN 10
DRIVER 3 OUT 11
RX5 IN 12
ON/OFF 13
3V V
L
14
28 V
–
27 C2
–
26 C2
+
25 DRIVER 1 IN
24 RX1 OUT
23 DRIVER 2 IN
22 RX2 OUT
21 RX3 OUT
20 RX4 OUT
19 DRIVER 3 IN
18 RX5 OUT
17 GND
16 DRIVER
DISABLE
15 NC
Supply Voltage (V
CC
) ................................................ 6V
Supply Voltage (V
L
) .................................................. 6V
V
+
........................................................................ 13.2V
V
–
...................................................................... –13.2V
Input Voltage
Driver ........................................................... V
–
to V
+
Receiver ................................................ – 30V to 30V
Output Voltage
Driver .................................................... – 30V to 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
ORDER PART
NUMBER
LT1342CG
LT1342CNW
LT1342CSW
G PACKAGE
NW PACKAGE
28-LEAD PLASTIC SSOP 28-LEAD WIDE PDIP
SW PACKAGE
28-LEAD WIDE PLASTIC SO
T
JMAX
= 125°C,
θ
JA
= 96°C/ W (G)
T
JMAX
= 125°C,
θ
JA
= 56°C/ W (NW)
T
JMAX
= 125°C,
θ
JA
= 85°C/ W (SW)
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
PARAMETER
Power Supply Generator
V
+
Output
V
–
Output
Supply Current (V
CC
)
Logic Supply Current (V
L
)
Supply Current When OFF (V
CC
)
Logic Supply Current (V
L
) When OFF
Supply Rise Time
Shutdown to Turn-On
ON/OFF Pin Thresholds
ON/OFF Pin Current
DRIVER DISABLE Pin Thresholds
DRIVER DISABLE Pin Current
Oscillator Frequency
CONDITIONS
(Note 2)
MIN
TYP
8.6
–7
12
0.1
1
3
1
0.1
0.2
1.4
1.4
1.4
1.4
130
MAX
UNITS
V
V
mA
mA
µA
mA
µA
mA
ms
V
V
µA
V
V
µA
kHz
(Note 3)
(Note 4)
Shutdown (Note 5)
Driver Disable
Shutdown (Note 5)
Driver Disable
C1 = C2 = 0.2µF,
C
+
= C
–
= 0.1µF
Input Low Level (Device Shutdown)
Input High Level (Device Enabled)
0V
≤
V
ON/OFF
≤
5V
Input Low Level (Drivers Enabled)
Input High Level (Drivers Disabled)
0V
≤
V
DRIVER DISABLE
≤
5V
q
q
17
1
10
10
1
q
q
q
q
q
q
0.8
80
0.8
500
2.4
–15
2.4
–10
2
U
W
U
U
W W
W
LT1342
ELECTRICAL CHARACTERISTICS
PARAMETER
Any Driver
Output Voltage Swing
Logic Input Voltage Level
Logic Input Current
Output Short-Circuit Current
Output Leakage Current
Data Rate (Note 8)
Slew Rate
Propagation Delay
Any Receiver
Input Voltage Thresholds
Hysteresis
Input Resistance
Output Leakage Current
Receivers 1 Through 4
Output Voltage
Output Short-Circuit Current
Propagation Delay
Receiver 5
Output Voltage
Output Short-Circuit Current
Propagation Delay
CONDITIONS
Load = 3k to GND
(Note 2)
MIN
Positive
Negative
q
q
q
q
q
TYP
7.3
– 6.5
1.4
1.4
5
17
10
MAX
UNITS
V
V
V
V
µA
mA
µA
kBaud
kBaud
V/µs
V/µs
µs
µs
V
V
V
kΩ
µA
V
V
mA
mA
ns
ns
V
V
mA
mA
µs
µs
5
Input Low Level (V
OUT
= High)
Input High Level (V
OUT
= Low)
0.8V
≤
V
IN
≤
2V
V
OUT
= 0V
Shutdown, V
OUT
=
±30V
(Note 5)
R
L
= 3k, C
L
= 2500pF
R
L
= 3k, C
L
= 1000pF
R
L
= 3k, C
L
= 51pF
R
L
= 3k, C
L
= 2500pF
Output Transition t
HL
High to Low (Note 6)
Output Transition t
LH
Low to High
Input Low Threshold (V
OUT
= High)
Input High Threshold (V
OUT
= Low)
–5
0.8
20
100
2
±9
q
120
250
4
15
6
0.6
0.5
1.3
1.7
0.4
5
1
0.2
2.9
– 20
20
250
350
0.2
2.9
–4
4
1
1
30
1.3
1.3
0.8
q
0.1
3
Shutdown (Note 4) 0
≤
V
OUT
≤
V
CC
Output Low, I
OUT
= – 1.6mA
Output High, I
OUT
= 160µA
Sinking Current, V
OUT
= V
CC
Sourcing Current, V
OUT
= 0V
Output Transition t
HL
High to Low (Note 7)
Output Transition t
LH
Low to High
Output Low, I
OUT
= – 500µA
Output High, I
OUT
= 160µA
Sinking Current, V
OUT
= V
CC
Sourcing Current, V
OUT
= 0V
Output Transition t
HL
High to Low (Note 7)
Output Transition t
LH
Low to High
q
q
q
2.4
1
7
10
0.4
–10
600
600
0.4
–2
3
3
2.7
10
q
q
2.7
2
The
q
denotes specifications which apply over the full operating
temperature range (0°C
≤
T
A
≤
70°C for commercial 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, V
L
= 3.3V and V
ON/OFF
= 3V.
Note 3:
Supply current is measured with external capacitors C
+
= C
–
= 0.1µF, C1 = C2 = 0.2µF. All outputs are open with all driver inputs
tied high.
Note 4:
V
L
supply current is measured with all receiver outputs high.
Note 5:
Supply current and leakage measurements in shutdown are
performed with V
ON/OFF
≤
0.1V. Supply current measurements using driver
disable are performed with V
DRIVER DISABLE
≥
3V.
Note 6:
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 7:
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 8:
Data rate operation guaranteed by slew rate, short-circuit current
and propagation delay tests.
3
LT1342
TYPICAL PERFOR A CE CHARACTERISTICS
Driver Output Voltage
10
8
DRIVER OUTPUT VOLTAGE (V)
R
L
= 3k
OUTPUT HIGH
THRESHOLD VOLTAGE (V)
6
4
2
0
–2
–4
–6
–8
–10
–55 –25
2.25
2.00
1.75
1.50
1.25
1.00
0.75
INPUT LOW
INPUT HIGH
SUPPLY CURRENT (mA)
V
CC
= 5.5V
V
CC
= 5V
V
CC
= 4.5V
V
CC
= 4.5V
V
CC
= 5V
V
CC
= 5.5V
OUTPUT LOW
50
25
0
75
TEMPERATURE (°C)
100
125
Supply Current in Shutdown
150
125
100
75
50
25
0
–55 –25
SUPPLY CURRENT (mA)
THRESHOLD VOLTAGE (V)
SUPPLY CURRENT (µA)
50
25
75
0
TEMPERATURE (°C)
ON/OFF Thresholds
3.0
2.5
THRESHOLD VOLTAGE (V)
40
35
SUPPLY CURRENT (mA)
30
25
20
15
10
5
LEAKAGE CURRENT (
µA)
2.0
1.5
1.0
ON THRESHOLD
OFF THRESHOLD
0.5
0
–55 –25
50
25
75
0
TEMPERATURE (°C)
4
U W
LT1342 • TPC01
Receiver Input Thresholds
3.00
2.75
2.50
Supply Current vs Data Rate
80
70
60
50
40
30
20
10
3DRIVERS ACTIVE
R
L
= 3k
C
L
= 2500pF
0.50
–55 –25
50
25
0
75
TEMPERATURE (°C)
100
125
0
0
25
75
50
100
DATA RATE (kBAUD)
125
150
LT1342 • TPC02
LT1342 • TPC03
Supply Current in Driver Disable
5
3.0
2.5
2.0
1.5
1.0
0.5
Driver Disable Threshold
4
3
2
1
100
125
0
–55 –25
50
25
0
75
TEMPERATURE (°C)
100
125
0
–55 –25
50
25
75
0
TEMPERATURE (°C)
100
125
LT1342 • TPC04
LT1342 • TPC05
LT1342 • TPC06
Supply Current
100
Driver Leakage in Shutdown
3DRIVERS LOADED R
L
= 3k
2DRIVERS LOADED R
L
= 3k
1DRIVER LOADED R
L
= 3k
NO LOAD
10
1
V
OUT
= 30V
V
OUT
= –30V
100
125
0
–55 –25
50
25
0
75
TEMPERATURE (°C)
100
125
0.1
–55 –25
50
25
0
75
TEMPERATURE (°C)
100
125
LT1342 • TPC07
LT1341 • TPC08
LT1342 • TPC09
LT1342
TYPICAL PERFOR A CE CHARACTERISTICS
Driver Short-Circuit Current
30
SHORT-CIRCUIT CURRENT (mA)
25
20
15
SHORT-CIRCUIT CURRENT (mA)
10
5
0
–55 –25
50
25
75
0
TEMPERATURE (°C)
Receiver Output Waveforms
RX5 OUTPUT
C
L
= 50pF
DRIVER OUTPUT
R
L
= 3k
RX1 TO RX4
OUTPUT
C
L
= 50pF
INPUT
V
L
= 3V
LT1342 • TPC12
PI FU CTIO S
V
CC
:
5V Input Supply Pin. This pin should be decoupled
with a 0.1µF ceramic capacitor close to the package pin.
Insufficient supply bypassing can result in low output
drive levels and erratic charge pump operation.
V
L
:
3V Logic Supply Pin. Provides power to the receiver
outputs. Decouple with a 0.1µF ceramic capacitor.
GND:
Ground Pin.
ON/OFF:
A TTL/CMOS Compatible Operating Mode Con-
trol. A logic low puts the device in the low power shutdown
mode. Drivers and receivers assume a high impedance
state in shutdown. The transceiver consumes almost no
supply current while in shutdown. A logic high fully
enables the transceiver. An ON/OFF logic low signal super-
sedes the state of the DRIVER DISABLE pin.
DRIVER DISABLE:
This pin provides an alternate control
for the charge pump and RS232 drivers. A logic high on
this pin shuts down the charge pump and places all drivers
in a high impedance state. All five receivers remain active
under these conditions. Floating the DRIVER DISABLE pin
or driving it to a logic low level fully enables the trans-
ceiver. A logic low on the ON/OFF pin supersedes the state
of the DRIVER DISABLE pin. Supply current drops to 3mA
when in driver disable mode.
V
+
:
Positive Supply Output (RS232 Drivers). V
+
≈
2V
CC
–
1.5V. This pin requires an external charge storage capaci-
tor C
≥
0.1µF, tied to ground or V
CC
. With multiple
transceivers, the V
+
and V
–
pins may be paralleled into
common charge storage capacitors. Larger value capaci-
tors may be used to reduce supply ripple.
U W
Receiver Short-Circuit Current
50
I
SC+
40
RX1 TO RX4
I
SC–
RX1 TO RX4
I
SC+
RX5 I
SC–
30
I
SC–
20
10
RX5 I
SC+
100
125
0
–55 –25
50
25
0
75
TEMPERATURE (°C)
100
125
LT1342 • TPC10
LT1342 • TPC11
Driver Output Waveforms
DRIVER OUTPUT
R
L
= 3k
C
L
= 2500pF
INPUT
LT1342 • TPC13
U
U
U
5
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