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PDF LT1281A Data sheet ( Hoja de datos )
| Número de pieza | LT1281A | |
| Descripción | Low Power 5V RS232 Dual Driver/Receiver with 0.1uF Capacitors | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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FEATURES
s 10mA Max Supply Current
s ESD Protection over ±10kV
s Uses Small Capacitors: 0.1µF
s 120kBaud Operation for RL = 3k, CL = 2500pF
s 250kBaud Operation for RL = 3k, CL = 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 Available in SO Package
APPLICATI S
s Portable Computers
s Battery-Powered Systems
s Power Supply Generator
s Terminals
s Modems
TYPICAL APPLICATI
+
0.1µF
2
4
+
0.1µF
LOGIC
INPUTS
5
6
12
11
13
LOGIC
OUTPUTS
10
ON/OFF
18
LT1280A
17
5V INPUT
3
+
V+ OUT
0.1µF
7
+
0.1µF
V – OUT
15 RS232 OUTPUT
8
14
5k
9
5k 16
RS232 OUTPUT
RS232 INPUT
RS232 INPUT
LT1280A • TA01
LT1280A/LT1281A
Low Power 5V RS232
Dual Driver/Receiver with
0.1µF Capacitors
DESCRIPTIO
The LT®1280A/LT1281A are dual RS232 driver/receiver
pairs with integral charge pump to generate RS232 volt-
age levels from a single 5V supply. These circuits feature
rugged bipolar design to provide operating fault tolerance
and ESD protection unmatched by competing CMOS
designs. Using only 0.1µF external capacitors, these cir-
cuits consume only 40mW of power, and can operate to
120kbaud even while driving heavy capacitive loads. New
ESD structures on the chip allow the LT1280A/LT1281A to
survive multiple ±10kV strikes, eliminating the need for
costly TransZorbs® on the RS232 line pins. The LT1280A/
LT1281A 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 LT1281A is available in 16-pin DIP and SO packages.
The LT1280A is supplied in 18-pin DIP and SO packages
for applications which require shutdown.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TransZorb is a registered trademark of General Instruments, GSI
DRIVER
OUTPUT
RL = 3k
CL = 2500pF
RECEIVER
RCOL U=T5P0UpTF
INPUT
Output Waveforms
LT1280A • TA02
1
1 page  
TYPICAL PERFOR A CE CHARACTERISTICS
LT1280A/LT1281A
DRIVER 1
OUTPUT
Shutdown to Driver Outputs
10V
5V
GND
GND
DRIVER 2 – 5V
OUTPUT
– 10V
ON/OFF PIN
LT1280A • TPC12
Driver Output Waveforms
DRIVER OUTPUT
RL = 3k
CL = 2500pF
DRIVER OUTPUT
RL = 3k
INPUT
LT1280A • TPC13
PI FU CTIO S
VCC: 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.
GND: Ground Pin.
ON/OFF: A TTL/CMOS Compatible Operating Mode Con-
trol. A logic low puts the LT1280A in shutdown mode.
Supply current drops to zero and both driver and receiver
outputs assume a high impedance state. A logic high fully
enables the device.
V+: Positive Supply Output (RS232 Drivers). V+ ≈ 2VCC –
1.5V. This pin requires an external charge storage capaci-
tor C ≥ 0.1µF, tied to ground or VCC. Larger value capaci-
tors may be used to reduce supply ripple. With multiple
transceivers, the V+ and V – pins may be paralleled into
common capacitors.
V–: Negative Supply Output (RS232 Drivers). V – ≈ –
(2VCC – 2.5V). This pin requires an external charge storage
capacitor C ≥ 0.1µF. Larger value capacitors may be used
to reduce supply ripple. With multiple transceivers, the V+
and V – pins may be paralleled into common capacitors.
TR1 IN, TR2 IN: RS232 Driver Input Pins. These inputs are
TTL/CMOS compatible. Inputs should not be allowed to
float. Tie unused inputs to VCC.
TR1 OUT, TR2 OUT: Driver Outputs at RS232 Voltage
Levels. Driver output swing meets RS232 levels for loads
up to 3k. Slew rates are controlled for lightly loaded lines.
Output current capability is sufficient for load conditions
up to 2500pF. Outputs are in a high impedance state when
in shutdown mode or VCC = 0V. Outputs are fully short-
circuit protected from V – + 30V to V + – 30V. Applying
higher voltages will not damage the device if the overdrive
is moderately current limited. Short circuits on one
output can load the power supply generator and may
disrupt the signal levels of the other outputs. The driver
outputs are protected against ESD to ±10kV for human
body model discharges.
REC1 IN, REC2 IN: Receiver Inputs. These pins accept
RS232 level signals (±30V) into a protected 5k terminat-
ing resistor. The receiver inputs are protected against ESD
to ±10kV for human body model discharges. Each receiver
provides 0.4V of hysteresis for noise immunity. Open
receiver inputs assume a logic low state.
REC1 OUT, REC2 OUT: Receiver outputs with TTL/CMOS
Voltage Levels. Outputs are in a high impedance state
when in shutdown mode to allow data line sharing. Out-
puts are fully short-circuit protected to ground or VCC with
the power ON, OFF or in the shutdown mode.
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 –. C1 should
be deleted if a separate 12V supply is available and
connected to pin C1+. Similarly, C2 should be deleted if a
separate – 12V supply is connected to pin V –.
5
5 Page | ||
| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet LT1281A.PDF ] | |
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