MC145403

•MC145404•MC145405•MC145408

MOTOROLA

5

Figure 1. Power–Off Source Resistance

Illustrated for MC145408

DI5

14

124

11

VDD

16

18

20

22

9

3

5

7

13

12

GND

VDD VCC

DI4

DI3

DI2

DI1

Tx5

Tx4

Tx3

Tx2

Tx1

Vin = ± 2 V

R

V

in

I

Figure 2. Switching Characteristics

50%

DI

+ 3 V

0 V

tf

10%

90%

tr

tPHL

tPLH

VOL

VOH

Tx

DRIVERS

50%

Rx

+ 3 V

0 V

tf

10%

90%

tr

tPHL

tPLH

VOL

VOH

DO

RECEIVERS

Figure 3. Slew Rate Characteristics

Tx

+ 3 V

tSHL

DRIVERS

+ 3 V

tSLH

– 3 V

– 3 V

Slew Rate =

6 V

tSLH or tSHL

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 – Rx

n

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 – DO

n

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.