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FAST AND LS TTL DATA

MC74F258A

AC CHARACTERISTICS

74F

74F

TA = +25°C

TA = 0°C to 70°C

VCC = +5.0 V

VCC = 5.0 V ± 10%

CL = 50 pF

CL = 50 pF

Symbol

Parameter

Min

Max

Min

Max

Unit

tPLH

Propagation Delay

2.5

5.3

2.0

6.0

ns

tPHL

In to Zn

1.0

4.0

1.0

5.0

tPLH

Propagation Delay

3.0

7.5

3.0

8.5

ns

tPHL

S to Zn

2.5

7.0

2.5

8.0

tPZH

Output Enable Time

2.0

6.0

2.0

7.0

ns

tPZL

2.5

7.0

2.5

8.0

tPHZ

Output Disable Time

2.0

6.0

2.0

7.0

ns

tPLZ

1.5

6.0

1.5

7.0

FUNCTIONAL DESCRIPTION

The F258A is a quad 2-input multiplexer with 3-state out-

puts. It selects four bits of data from two sources under control

of a common Select input (S). When the Select input is LOW,

the I0x inputs are selected and when Select is HIGH, the I1x

inputs are selected. The data on the selected inputs appears

at the outputs in inverted form. The F258A is the logic imple-

mentation of a 4-pole, 2-position switch where the position of

the switch is determined by the logic levels supplied to the Se-

lect input. The logic equations for the outputs are shown be-

low:

Za = OE • (I1a • S + I0a • S)

Zb = OE • (I1b • S + I0b • S)

Zc = OE • (I1c • S + I0c • S)

Zd = OE • (I1d • S + I0d • S)

When the Output Enable input (OE) is HIGH, the outputs are

forced to a high impedance OFF state. If the outputs of the

3-state devices are tied together, all but one device must be in

the high impedance state to avoid high currents that would ex-

ceed the maximum ratings. Designers should ensure the Out-

put Enable signals to 3-state devices whose outputs are tied

together are designed so there is no overlap.