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PDF MC1488 Data sheet ( Hoja de datos )
| Número de pieza | MC1488 | |
| Descripción | RS232C QUAD LINE DRIVER | |
| Fabricantes | ST Microelectronics | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de MC1488 (archivo pdf) en la parte inferior de esta página. Total 9 Páginas | ||
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® MC1488
RS232C QUAD LINE DRIVER
s CURRENT LIMITED OUTPUT ±10mA TYP.
s POWER-OFF SOURCE IMPEDANCE 300Ω
MIN.
s SIMPLE SLEW RATE CONTROL WITH
EXTERNAL CAPACITOR
s FLEXIBLE OPERATING SUPPLY RANGE
s INPUTS ARE TTL AND µP COMPATIBLE
DESCRIPTION
The MC1488 is a monolithic quad line driver
designed to interface data terminal equipment
with data communications equipment in
conformance with the specifications of EIA
Standard No. RS232C.
P
DIP14
(Plastic Package)
D
SO14
(Plastic Micropackage)
ORDER CODES :
MC1488P (Plastic DIP)
MC1488D (SO14)
PIN CONNECTIONS (top view)
LOGIC DIAGRAM
March 2000
1/9
1 page  
TYPICAL APPLICATION : RS232C Data Transmission
MC1488
APPLICATION INFORMATION
The Electronic Industries Association (EIA) has
released the RS232C specification detailing the
requirements for the interface between data
processing equipment. This standard specifies
not only the number and type of interface leads,
but also the voltage levels to be used. The
MC1488 quad driver and its companion circuit,
the MC1489 quad receiver, provide a complete
interface system between DTL or TTL logic levels
and the RS232C defined levels. The RS232C
requirements as applied to drivers are discussed
herein.
The required driver voltages are defined as
between 5 and 15 V in magnitude and are
positive for a logic ”0” and negative for a logic ”1”.
These voltages are so defined when the drivers
are terminated with a 3000 to 7000Ω resistor.
The MC1488 meets this voltage requirement by
converting a DTL/TTL logic level into RS232C
levels with one stage of inversion.
The RS232C specification further requires that
during transitions, the driver output slew rate
must not exceed 30 V per µs. The inherent slew
rate of the MC1488 is much too fast for this
requirement. The current limited output of the
device can be used to control this slew rate by
connecting a capacitor to each driver output. The
required capacitor can be easily determined by
using the relationship C = IOS x ∆T/ ∆V from
which Figure 12 is derived. Accordingly, a 330 pF
capacitor on each output will guarantee a worst
case slew rate of 30 V per µs.
The interface driver is also required to withstand
an accidental short to any other conductor in an
interconnecting cable. The worst possible signal
on any conductor would be another driver using a
plus or minus 15 V, 500 mA source. The MC1488
is designed to indefinitely withstand such a short
to all four outputs in a package as long as the
power-supply voltages are greater than 9.0 V
(i.e., VS ≥ 9.0 V ; VEE ≤ - 9.0 V). In some
power-supply designs, a loss of system power
causes a low impedance on the power-supply
outputs. When this occurs, a low impedance to
ground would exist at the power inputs to the
MC1488 effectively shorting the 300Ω output
resistor to ground. If all four outputs were then
shorted to plus or minus 15 V, the power
dissipation in these resistors would be excessive.
Therefore, if the system is designed to permit low
impedances to ground at the power-suppies of
the drivers, a diode should be placed in each
power-supply lead to prevent over-heating in this
fault condition. These two diodes, as shown in
Figure 13, could be used to decouple all the
driver packages in a system. (These same diodes
will allow the MC1488 to withstand momentary
shorts to the ±15 V limits specified in the earlier
5/9
5 Page | ||
| Páginas | Total 9 Páginas | |
| PDF Descargar | [ Datasheet MC1488.PDF ] | |
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