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PDF LT1381 Data sheet ( Hoja de datos )
| Número de pieza | LT1381 | |
| Descripción | Low Power 5V RS232 Dual Driver/Receiver with 0.1uF Capacitors | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LT1381 (archivo pdf) en la parte inferior de esta página. Total 8 Páginas | ||
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FEATURES
s ESD Protection over ±10kV
s Low Cost
s Uses Small Capacitors: 0.1µF
s CMOS Comparable Low Power: 40mW
s Operates from a Single 5V Supply
s 120kBaud Operation for RL = 3k, CL = 2500pF
s 250kBaud Operation for RL = 3k, CL = 1000pF
s Rugged Bipolar Design
s Outputs Assume a High Impedance State When
Powered Down
s Absolutely No Latchup
s Available in Narrow SO Package
APPLICATI S
s Portable Computers
s Battery-Powered Systems
s Power Supply Generator
s Terminals
s Modems
TYPICAL APPLICATI
+
0.1µF
1
3
+
0.1µF
LOGIC
INPUTS
4
5
11
10
12
LOGIC
OUTPUTS
9
LT1381
16
5V INPUT
2
+
V+ OUT
0.1µF
6 V – OUT
+ 0.1µF
14
RS232 OUTPUT
7
13
5k
8
S
5k 15
RS232 OUTPUT
RS232 INPUT
RS232 INPUT
LT1381 • TA01
LT1381
Low Power 5V RS232 Dual
Driver/Receiver with
0.1µF Capacitors
DESCRIPTIO
The LT®1381 is a dual RS232 driver/receiver pair with
integral charge pump to generate RS232 voltage levels
from a single 5V supply. The circuit features rugged
bipolar design to provide operating fault tolerance and
ESD protection unmatched by competing CMOS designs.
Using only 0.1µF external capacitors, the circuit con-
sumes only 40mW of power and can operate to 120kbaud
even while driving heavy capacitive loads. New ESD struc-
tures on the chip allow the LT1381 to survive multiple
±10kV strikes, eliminating the need for costly TransZorbs®
on the RS232 line pins. Driver outputs are protected from
overload and can be shorted to ground or up to ±25V
without damage. During power-off conditions, driver and
receiver outputs are in a high impedance state, allowing
line sharing.
, 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
ROUTPUT
CL = 50pF
INPUT
Output Waveforms
LT1381 • TA02
1
1 page  
LT1381
PI FU CTIO S
C1+, C1–, C2 +, C2 – (Pins 1, 3, 4, 5): Commutating
Capacitor Inputs. These pins require two external capaci-
tors C ≥ 0.1µF: one from C1+ to C1– and another from C2+
to C2 –. C1 may be deleted if a separate 12V supply is
available and connected to pin C1+.
V+ (Pin 2): Positive Supply Output (RS232 Drivers).
V+ ≈ 2VCC – 2.1V. This pin requires an external charge
storage capacitor C ≥ 0.1µF, tied to ground or VCC. Larger
value capacitors may be used to reduce supply ripple. With
multiple transceivers, the V+ and V – pins may be paralleled
into common capacitors.
V– (Pin 6): Negative Supply Output (RS232 Drivers).
V – ≈ –(2VCC – 3V). This pin requires an external charge
storage capacitor C ≥ 0.1µF. Larger value capacitors may
be used to reduce supply ripple. With multiple transceiv-
ers, the V+ and V – pins may be paralleled into common
capacitors.
TR2 OUT, TR1 OUT (Pin 7, 14): 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 VCC = 0V. Outputs are fully short-
circuit protected from V – + 25V to V + – 25V. Applying
higher voltages will not damage the device if the over-
drive 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.
REC2 IN, REC1 IN (Pins 8, 13): Receiver Inputs. These
pins accept RS232 level signals (±30V) into a protected 5k
terminating resistor. The receiver inputs are protected
against ESD to ±10kV for human body model discharges.
Each receiver provides 0.4V of hysteresis for noise immu-
nity. Open receiver inputs assume a logic low state.
REC2 OUT, REC1 OUT (Pins 9, 12): Receiver Outputs with
TTL/CMOS Voltage Levels. Outputs are fully short-circuit
protected to ground or VCC with the power ON or OFF.
TR2 IN, TR1 IN (Pins 10, 11): RS232 Driver Input Pins.
These inputs are TTL/CMOS compatible. Inputs should
not be allowed to float. Tie unused inputs to VCC.
GND (Pin 15): Ground Pin.
VCC (Pin 16): 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.
U
ESD PROTECTIO
The RS232 line inputs of the LT1381 have on-chip protec-
tion from ESD transients up to ±10kV. The protection
structures act to divert the static discharge safely to
system ground. In order for the ESD protection to function
effectively, the power supply and ground pins of the circuit
must be connected to ground through low impedances.
The power supply decoupling capacitors and charge pump
storage capacitors provide this low impedance in normal
application of the circuit. The only constraint is that low
ESR capacitors must be used for bypassing and charge
storage. ESD testing must be done with pins VCC, V+, V –
and GND shorted to ground or connected with low ESR
capacitors.
ESD Test Circuit
+
0.1µF
1 C1+
0.1µF
+ 2 V+
LT1381
5V VCC 16
15
GND
3 C1–
TR1 OUT 14
+
0.1µF
0.1µF
+
4 C2+
5 C2–
6 V–
REC1 IN 13
REC1 OUT 12
TR1 IN 11
RS232
LINE PINS
PROTECTED
TO ±10kV
7 TR2 OUT
8 REC2 IN
TR2 IN 10
REC2 OUT 9
+
0.1µF
RS232
LINE PINS
PROTECTED
TO ±10kV
LT1381 • ESD TC
5
5 Page | ||
| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet LT1381.PDF ] | |
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