MC1488MG ON Semiconductor, MC1488MG Datasheet - Page 6

• Manufacturer Part Number: MC1488MG
• Description: IC LINE DRIVER QD MONO 14SOEIAJ
• Manufacturer: ON Semiconductor
• Type: Driverr

Specifications of MC1488MG

• Number Of Drivers/receivers: 4/0
• Protocol: RS232
• Voltage - Supply: 15V
• Mounting Type: Surface Mount
• Package / Case: 14-SOIC (5.3mm Width), 14-SOP, 14-SOIJ
• Interface: EIA-232-D
• Maximum Operating Temperature: + 75 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: 0 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

specification details the requirements for the interface
between
communications 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 EIA−232D defined levels. The EIA−232D
requirements as applied to drivers are discussed herein.
5.0 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 7000 W
resistor. The MC1488 meets this voltage requirement by
converting a DTL/TTL logic level into EIA−232D levels
with one stage of inversion.
during transitions, the driver output slew rate must not
exceed 30 V per microsecond. 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 = I
derived. Accordingly, a 330 pF capacitor on each output
will guarantee a worst case slew rate of 30 V per
microsecond.
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., V
1000
100
1.0
10
The Electronic Industries Association EIA−232D
The required driver voltages are defined as between
The EIA−232D specification further requires that
The interface driver is also required to withstand an
1.0
30 V/ms
Figure 14. Slew Rate versus Capacitance
data
10
OS
CC
processing
x DT/DV from which Figure 14 is
q 9.0 V; V
for I
C, CAPACITANCE (pF)
SC
= 10 mA
100
equipment
EE
p − 9.0 V). In some
333 pF
1,000
APPLICATIONS INFORMATION
and
http://onsemi.com
10,000
data
6
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 300 W output
resistors 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 supplies of
the drivers, a diode should be placed in each power supply
lead to prevent overheating in this fault condition. These two
diodes, as shown in Figure 15, 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
±25 V limits specified in the earlier Standard EIA−232B.)
The addition of the diodes also permits the MC1488 to
withstand faults with power supplies of less than the 9.0 V
stated above.
fault conditions is more than guaranteed by the previously
mentioned 10 mA output current limiting.
Other Applications
a myriad of possible applications. Several features of the
drivers enhance this versatility:
designer to define the output voltage levels independent of
power supplies and can be accomplished by diode
clamping of the output pins. Figure 16 shows the MC1488
used as a DTL to MOS translator where the high level
voltage output is clamped one diode above ground. The
resistor divider shown is used to reduce the output voltage
below the 300 mV above ground MOS input level limit.
V
V
CC
EE
The maximum short circuit current allowable under
The MC1488 is an extremely versatile line driver with
1. Output Current Limiting − this enables the circuit
7
Figure 15. Power Supply Protection
to Meet Power Off Fault Conditions
MC1488
14
1
7
MC1488
14
1
7
MC1488
14
1