22
20
18
16
14
24
VDD VCC
3
DI1
Tx1
DI2
DI3
DI4
DI5
VDD
12
Tx2
Tx3
Tx4
Tx5
GND
13
5
7
9
11
R
out
Vin =
±
2 V
1
+
VI
in
Figure 1. Power–Off Source Resistance
Illustrated for MC145408
DRIVERS
+3V
DI
50%
0V
tf
Tx
tPHL
RECEIVERS
+3V
Rx
50%
0V
tPHL
90%
DO
10%
tf
tr
tPLH
VOH
VOL
Tx
90%
10%
tPLH
DRIVERS
+3V
–3V
tSHL
Slew Rate =
6V
tSLH or tSHL
+3V
–3V
tSLH
VOL
tr
VOH
Figure 2. Switching Characteristics
Figure 3. Slew Rate Characteristics
PIN DESCRIPTIONS
VCC
Digital Power Supply
The digital supply pin, which is connected to the logic
power supply (+ 5.5 V maximum).
GND
Ground
Ground return pin is typically connected to the signal
ground pin of the EIA–232–E connector (Pin 7) as well as to
the logic power supply ground.
VDD
Most Positive Device Pin
The most positive power supply pin, which is typically + 5
to + 12 V.
VSS
Most Negative Device Pin
The most negative power supply pin, which is typically – 5
to – 12 V.
Rx1 – Rxn
Receive Data Input Pins
These are the EIA–232–E receive signal inputs. A voltage
between + 3 and + 25 V is decoded as a space, and causes
the corresponding DO pin to swing to ground (0 V). A voltage
between – 3 and – 25 V is decoded as a mark, and causes
the corresponding DO pin to swing to VCC.
DO1 – DOn
Data Output Pins
These are the receiver digital output pins which swing from
VCC to GND. Each output pin is capable of driving one
LSTTL input load.
MOTOROLA
MC145403•MC145404•MC145405•MC145408
5
MOTOROLA [ MOTOROLA, INC ]
