MC74HCT157A

High–Speed CMOS Logic Data

DL129 — Rev 6

3

MOTOROLA

Sb l

P

Guaranteed Limit

Ui

Symbol

Parameter

– 55 to

25

_C

v 85_C

v 125_C

Unit

tPLH,

tPHL

Maximum Propagation Delay, Input A or B to Output Y

(Figures 1 and 4)

27

34

41

ns

tPLH,

tPHL

Maximum Propagation Delay, Select to Output Y

(Figures 2 and 4)

37

46

56

ns

tPLH,

tPHL

Maximum Propagation Delay, Output Enable to Output Y

(Figures 3 and 4)

30

38

45

ns

tTLH,

tTHL

Maximum Output Transition Time, Any Output

(Figures 1 and 4)

15

19

22

ns

tr, tf

Maximum Input Rise and Fall Time

500

500

500

ns

NOTE: For propagation delays with loads other than 50 pF, and information on typical parametric values, see Chapter 2 of the Motorola High–

Speed CMOS Data Book (DL129/D).

C

P

Di

i

i

C

i

(P

T

i

Ch

l)*

Typical @ 25

°C, VCC = 5.0 V

F

CPD

Power Dissipation Capacitance (Per Transceiver Channel)*

64

pF

* Used to determine the no–load dynamic power consumption: PD = CPD VCC2f + ICC VCC. For load considerations, see Chapter 2 of the

Motorola High–Speed CMOS Data Book (DL129/D).

PIN DESCRIPTIONS

INPUTS

A0, A1, A2, A3 (Pins 2, 5, 11, 14)

Nibble A inputs. The data present on these pins is trans-

ferred to the outputs when the Select input is at a low level

and the Output Enable input is at a low level. The data is

presented to the outputs in noninverted form.

B0, B1, B2, B3 (Pins 3, 6, 10, 13)

Nibble B inputs. The data present on these pins is trans-

ferred to the outputs when the Select input is at a high level

and the Output Enable input is at a low level. The data is

presented to the outputs in noninverted form.

OUTPUTS

Y0, Y1, Y2, Y3 (Pins 4, 7, 9, 12)

Data outputs. The selected input Nibble is presented at

these outputs when the Output Enable input is at a low level.

The data is presented to the outputs in noninverted form. For

the Output Enable input at a high level, the outputs are at a

low level.

CONTROL INPUTS

Select (Pin 1)

Nibble select. This input determines the data word to be

transferred to the outputs. A low level on this input selects

the A inputs and a high level selects the B inputs.

Output Enable (Pin 15)

Output Enable input. A low level on this input allows the

selected input data to be presented at the outputs. A high

level on this input sets all outputs to a low level.