MC1488
ABSOLUTE MAXIMUM RATINGS
Symbo l
V
S
V
EE
V
IR
V
O
T
amb
T
stg
Parameter
Power Supply Voltage
Power Supply Voltage
Input Voltage Range
Output Signal Voltage
Operating Ambient Temperature
Storage Temperature Range
T est Cond ition s
15
–15
–15
≤
V
IR
≤
7
±
15
0 to 75
–65 to 150
Unit
V
V
V
V
o
C
o
C
THERMAL DATA
Symbol
Parameter
R
th j-amb
Thermal Resistance Junction-ambientMax.
Pl astic DIP14 Ceramic DIP14
200
o
C/W
165
o
C/W
SO14
165
o
C/W
ELECTRICAL CHARACTERISTICS
V
S
=
9
±10%V,
V
E E
= –9
±10%V
,T
amb
=
0 to 75
o
C, unless otherwise specified
Symbo l
Parameter
Input Current
I
IL
I
IH
V
OH
Input Current
Output Voltage
T est Conditio ns
Low Logic StateV
IL
= 0V
High Logic StateV
IH
= 5V
High Logic StateR
L
= 3k
Ω
V
IL
= 0.8V, V
S
= 9V, V
EE
= –9V
V
IL
= 0.8V, V
S
= 13.2V, V
EE
= –13.2V
Low Logic State
V
IH
= 1.9V, V
EE
= –9V, V
S
= 9V
V
IH
= 1.9V, V
EE
= –13.2V, V
S
= 13.2V
Min. Typ . Max. Un it F ig .
1
1.6 mA
1
10
µ
A
V
6
9
-6
-9
6
-6
300
7
10.5
V
-7
-10.5
mA
10
-10
15
4.5
19
5.5
12
mA
-12
Ω
20
6
25
7
34
12
-17
-15
-23
-15
-34
-2.5
333
567
4
V
S
= V
EE
= 0V
ol
=
±
2V
V
IH
= 1.9V
V
s
= 9V
V
s
= 9V
V
IL
= 0.8V
V
IH
= 1.9V
V
s
= 12V
V
s
= 12V
V
IL
= 0.8V
V
IH
= 1.9V
V
s
= 15V
V
s
= 15V
V
IL
= 0.8V
V
IH
= 1.9V
V
s
= -9V
V
s
= -9V
V
IL
= 0.8V
V
s
= -12V
V
IH
= 1.9V
V
s
= -12V
V
IL
= 0.8V
V
s
= -15V
V
IH
= 1.9V
V
s
= -15V
V
IL
= 0.8V
V
S
= 9V
V
EE
= -9V
V
EE
= -12V
V
S
= 12V
3
2
2
3
2
2
1
V
OL
Output Voltage
I
OS +
*
I
OS
*
R
O
I
s
–
Positive Output Short-circuit
Current
Negative Output Short-circuit
Current
Output Resistance
Positive Supply Current
(R
i
=
∞
)
mA
5
I
EE
Negative Supply Current
(R
L
=
∞
)
-13
-18
mA
µ
A
mA
µ
A
mA
mA
mW
5
P
c
Power Consumption
SWITCHING CHARACTERISTICS
V
S
=
±9 ±1V,
V
E E
= –
9
±1%V
,T
amb
=
25
o
C
Symb ol
Parameter
t
PHL
Propagation Delay Time
t
THL
t
PHL
t
THL
Fall Time
Propagation Delay Time
Rise Time
Test Co nditions
Z
i
= 3k
Ω
and 15pF
Z
i
= 3kΩ and 15pF
Z
i
= 3kΩ and 15pF
Z
i
= 3k
Ω
and 15pF
Min. T yp. Max. Unit F ig.
275 350
ns
6
45
110
55
75
175
100
ns
ns
ns
6
6
6
* Maximum package power dissipation may be exceeded if all outputs are shorted simultaneously.
2/9
MC1488
TYPICAL APPLICATION :
RS232C Data Transmission
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 = I
OS
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 ; V
EE
≤
- 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
Automotive Electronics
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