LT1331 Linear Technology, LT1331 Datasheet - Page 6

• Manufacturer Part Number: LT1331
• Description: 3V RS562 or 5V/3V RS232 Transceiver with One Receiver Active in Shutdown
• Manufacturer: Linear Technology

Power Saving Operational Modes
The LT1331 has both shutdown and driver disable oper-
ating modes. These operating modes can optimize power
consumption based upon applications needs.
The shutdown control turns off all circuitry except for
Low-Q RX5. RX5 operates entirely from the V
supply, so the power consumption from V
zero. The V
shutdwon, which may allow greater power savings in
some systems. When RX5 detects a signal, this informa-
tion can be used to wake up the system for full operation.
If more than one line must be monitored, the driver
disable mode provides a power efficient operating
option. The driver disable mode turns off the charge
pumps and RS232 drivers, but keeps all five receivers
active. Power consumption in driver disable mode is 3mA
from V
LT1331
A
Table 1. Commonly Used RS232 Interface Circuit Receiver Thresholds
MANUFACTURER
Linear Technology
Texas Instruments
Maxim
Sipex
Motorola
National
6
PPLICATI
L
and less than 100 A from V
CC
power supply may be turned off while in
O
U
S
PART NUMBER
SN75189A
SN75C185
DS14C89A
I FOR ATIO
MAX232A
All Others
MC1489A
SN75189
LT1137A
MAX232
MAX241
MC1489
DS1489
U
LT1080
LT1330
LT1281
SP232
SP301
W
CC
.
COMPATIBLE
CC
U
drops to
L
power
0.65
0.65
0.65
0.75
0.75
0.75
0.75
MIN
0.8
0.8
0.8
0.8
0.8
0.8
0.6
0.8
0.5
INPUT LOW THRESHOLD
Mixed 5V/3V Operation
When operated with V
RS232 drivers meet or exceed all RS232 or V.28 commu-
nication interface standards. Data rates up to 120kbaud
are supported, and all standard RS232 compatible mice
may be driven by the LT1331.
3V Operation
V
output swing than with V
when operated with V
least –2.7V to 3.7V, with typical swing being –3.3V to 4V.
This insures compatibility with all commonly used RS232
and RS562 interface circuits. Table 1 summarizes the
receiver input threshold specifications for RS232 circuits
from many manufacturers.
CC
= 3.3V operation of the LT1331 results in lower driver
TYP
1.3
1.3
1.3
1.3
1.0
1.0
1.2
1.0
1.3
1.2
1.2
0.8
1.0
–
–
–
MAX
1.25
1.25
1.25
1.35
1.25
1.25
1.25
1.9
–
–
–
–
–
–
–
–
CC
CC
CC
= 5V and V
= 3.3V, is guaranteed to be at
= 5V. The driver output swing,
MIN
1.55
1.75
1.75
0.9
1.6
1.0
1.0
1.3
–
–
–
–
–
–
–
–
INPUT HIGH THRESHOLD
L
= 3.3V supplies, the
1.95
1.25
TYP
1.7
1.7
1.7
1.7
1.3
1.9
1.7
2.1
1.8
1.5
1.7
–
–
–
MAX
2.25
2.55
2.25
2.4
2.4
2.4
2.4
1.6
2.4
2.4
2.4
2.4
2.5
1.5
1.5
2.7