March 2006 Rev 4 1/
17
MC1488
RS-232 quad line driver
General features
■Curren t limited output ±10m A typ.
■Power-off source impedance 300Ω min.
■Simple slew rate control with external capacitor
■Flexibl e operating supply range
■Inputs are TTL and µP compatible
Description
The MC1 488 is a monolithic quad line driver
designed to interface data terminal equipment
with data communications equipment in
conformance with the specifications of EIA
Standard N° RS232C.
SOP
DIP
www.st.com
Order codes
DIP14 SO14 (Tape & reel)
MC1488P MC1488D1013TR
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Contents MC1488
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Contents
1 Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Pin d escription . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5 Test circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
6 Typical applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.1 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
7 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
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MC1488 Diagram
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1 Diagram
Fi gure 1 . Logic diagram
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Pi n des cript io n MC1488
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2 Pin description
Fi gure 2 . P i n connections
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MC1488 M aximum ratings
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3 Maximum ra ting s
Note: Absolute Maximum Ratings are those values beyond which damage to the device may
occur. Function al operation under these cond ition is not implied.
Table 1. Absolute maximum ratings
Symbol Parameter Value Unit
VSPow e r s u pply voltage 1 5 V
VEE Pow e r s u pply v o ltage -15 V
VIR Input vol tage range VIR = -15 t o 7 V
VOOutput signal voltage ±15 V
Tamb Operating ambi ent t em perature 0 to 75 °C
Tstg Storage temperature range -65 to 150 °C
Table 2. Thermal data
Symbol Parameter Pl astic DIP14 SO14 Unit
RthJA Thermal resi stance junction-ambient Max 200 165 ° C/W
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Electri cal character istics MC1488
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4 Electrical characteristics
Table 3. El ectrical charac te ristics (VS = 9V ± 10%, VEE = -9 V ± 10%, Tamb = 0 to 75° C, unless
otherwise specified)
Symbol Parameter Test Conditions Min. Typ. Max. Unit
IIL Input Cur rent Figure 3 Low Logic State VIL = 0 V 1 1.6 mA
IIH Input Current Figure 3 Hi gh Logic State VIH = 5 V 10 µA
VOH Output Voltage Figure 4 High Logic State
RL = 3K,Ω
VIL = 0.8 V
VS = 9V, VEE = -9V 6 7 V
VS = 13V, VEE = -13V 9 10.5
VOL Output Voltage Figure 4 Low Logic Stat e
VIH = 1.9 V
VS = -9V, VEE = 9V -6 -7 V
VEE = -13.2V,
VS=13.2V -9 -10.5
IOS+(1)
1. Max imum package power diss ipation may be exceeded if all output s are shorted simultaneously.
Positive Output Short-
Circuit Current Figure 5 61012mA
IOS-(1) Negati ve Output Short-
Circuit Current Figure 5 -6 -10 -12 mA
ROOutp ut Resistance
Figure 6 VS = VEE = 0, VOL = ± 2V 300 Ω
IS
Positive Suppl y Current
(RI = ∞)
Figure 7
VIH = 1.9 V, VS = 9 V 15 2 0
mA
VIL = 0.8 V, VS = 9 V 4.5 6
VIH = 1.9 V, VS = 12 V 19 2 5
VIL = 0.8 V, VS = 12 V 5.5 7
VIH = 1.9 V, VS = 15 V 34
VIL = 0.8 V, VS = 15 V 12
IEE
Negati ve Supply Current
(RL = ∞)
Figure 7
VIH = 1.9 V, VS = -9 V -13 -17 m A
VIL = 0.8 V, VS = -9 V -1 5 µA
VIH = 1.9 V, VS = -12 V -18 -23 mA
VIL = 0.8 V, VS = -12 V -15 µA
VIH = 1.9 V, VS = -15 V -34 mA
VIL = 0.8 V, VS = -15 V -2.5
PCPower Consumption VS = 9 V, VEE = -9 V 333 mW
VS = 12 V, VEE = -12 V 567
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MC1488 Electrica l characteristics
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Table 4. Sw itching cha racteristic s (VS = 9 ± 1V, VEE = -9 ± 1V, Tamb = 25°C)
Symbol Parameter Test Conditions Min. Typ. Max. Unit
tPHL Propagation Delay Time
Figure 8 ZI = 3 KΩ and 15 pF 275 350 ns
tTHL Fall Time Figure 7 ZI = 3 KΩ and 15 pF 45 75 ns
tPHL Propagation Delay Time
Figure 8 ZI = 3 KΩ and 15 pF 110 175 ns
tTHL Fall Time Figure 8 ZI = 3 KΩ and 15 pF 55 100 ns
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Test circuit MC1488
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5 Test circuit
Figure 3. Input current
Figure 4. Output vol tage
Figure 5. Output short-circuit current
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MC1488 T est cir cuit
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Figure 6. Output resistance (power off)
Figure 7. Power supply currents
Figure 8. Switching response
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Test circuit MC1488
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Figure 9. Transfer characteristics vs
in p ut volta ge Figur e 10. Short-circuit output current
vs tempera ture
Figure 1 1. Output slew-rate load
capacitance Figur e 12. Output voltage and curr ent
limiting characteristics
Figure 13. Maximum operating
temperature vs power supply
voltage
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MC1488 Typ ical applications
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6 Typical applications
Figure 14. RS232C Data transmission
6.1 Application information
The Electronic Industries Association (EIA) has released the RS232C specification detailing
the requirements for the interface between data process ing equipme nt. 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 com plete interface system between DTL or TTL logic l evels and the RS232C
defined levels. The RS232C requirements as applied to drivers are discussed herein.
The required driver voltage s are defined as betwe en 5 and 15V in magnitude and are
positive for a logic "0" and negative for a logic "1". These v oltages are so defined when the
drivers are te rmina ted with a 3000 to 7000Ω resistor. The MC 1488 me ets this voltage
requirement by converting a DTL/TTL logic level into RS232C levels with one stage of
inversion.
The RS232C specifi cation further requires that during transitions, the driver output slew rate
must not exceed 30V 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 cap acitor can be easily
determined by using the relationship C = IOS x ∆T/∆V from which Figure 15. is derived.
Accordingly, a 330 pF capacitor on each out put will guarantee a worst case slew rat e of 30V
per µs.
The interface driv er 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 15V, 500 mA sourc e. The MC1488 is designed to indefinitely
withst and such a short to all f our outputs in a package as long as the power-supply voltages
are greater than 9.0V (i.e., VS ≥ 9.0V; VEE ≤ 9.0V). In some power-supply designs, a loss of
system power causes a low im pedance on the power-suppl y outputs. When this occurs, a
low impedance to ground would exist at the power inputs to the MC1488 effectively shorting
the 300W output resistor to ground. If all four outputs were then shorted to plus or minus
15V, the p o we r d i ssipat i on in these re si sto rs would be ex cessive. The re for e, if t he 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 over-heating in this f aul t condition.
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Typical applications MC1488
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These two diodes, as shown in Figure 13, could be used to decoupled all the driv er
packages in a syste m. (These same diodes will allow the MC1488 to withstand mo men tary
shorts to the ±15V limits spec ified in the earlier Standard RS232B ). The addition of the
diodes also permits the MC1488 to withstand faults wi th power-supp lies of less than the
9.0V stated above.
The maximum short-circ uit current allowable under fault conditions is more than guaranteed
by the previously mentioned 10 mA output current limiting.
The MC1488 is an extremely versatile line dr iver with a mired of possible applications.
Several features of the drivers enhance th is versat ility :
1. Output Current Limiting - this enabl es the circuit designer to define the output voltage
levels independent of power-supplies and can be accom plished by diode clamping of the
output pins.
2. Power-Supply Range - as can be seen from the schematic drawing of the drivers, th e
positive and negative driving elements of the device are essentially independent and do not
require matching power-supplies. In fact, the posit ive supply can very from a minimum
seven volts (required for driving the negative pulldown sec tion) to t he m axim um specified
15V. The negative supp ly can vary from approximately -2.5V to the minimum specified -
15V. The MC1488 will drive the out put to within 2V of the positive or ne gati ve supplies as
long as the current output limits are not exceeded. The combination of the current-limiting
and supply-voltage features allow a wide com bi nation of possible outputs within th e same
quad package.
Figure 15. Slew-rate load vs capacitan ce for ISC = 10mA
Figure 16. Power supply protection to meet Power-off fault conditions
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MC1488 Typ ical applications
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DIM. mm. inch
MIN. TYP MAX. MIN. TYP. MAX.
a1 0.51 0.020
B 1.39 1.65 0.055 0.065
b 0.5 0.020
b1 0.25 0.010
D 20 0.787
E 8.5 0.335
e 2.54 0.100
e3 15.24 0.600
F 7.1 0.280
I 5.1 0.201
L 3.3 0.130
Z 1.27 2.54 0.050 0.100
Plastic DIP-14 MECHANICAL DATA
P001A
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Typical applications MC1488
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DIM. mm. inch
MIN. TYP MAX. MIN. TYP. MAX.
A 1.35 1.75 0.053 0.069
A1 0.1 0.25 0.004 0.010
A2 1.10 1.65 0.043 0.065
B 0.33 0.51 0.013 0.020
C 0.19 0.25 0.007 0.010
D 8.55 8.75 0.337 0.344
E 3.8 4.0 0.150 0.157
e 1.27 0.050
H 5.8 6.2 0.228 0.244
h 0.25 0.50 0.010 0.020
L 0.4 1.27 0.016 0.050
k0°8°0°8°
ddd 0.100 0.004
SO-14 MECHANICAL DATA
0016019D
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MC1488 Typ ical applications
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DIM. mm. inch
MIN. TYP MAX. MIN. TYP. MAX.
A 330 12.992
C 12.8 13.2 0.504 0.519
D 20.2 0.795
N 60 2.362
T 22.4 0.882
Ao 6.4 6.6 0.252 0.260
Bo 9 9.2 0.354 0.362
Ko 2.1 2.3 0.082 0.090
Po 3.9 4.1 0.153 0.161
P 7.9 8.1 0.311 0.319
Tape & Reel SO-14 MECHANICAL DATA
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Revisi on history MC1488
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7 Revision history
Table 5. Revis ion history
Date Revision Changes
17-Mar-2006 4 Order codes has been updated and new template.
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MC1488
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