SN54/74LS398

• SN54/74LS399

AC SETUP REQUIREMENTS (TA = 25°C)

Symbol

Parameter

Limits

Unit

Test Conditions

Symbol

Parameter

Min

Typ

Max

Unit

Test Conditions

tW

Clock Pulse Width

20

ns

VCC = 5.0 V

ts

Data Setup Time

25

ns

VCC = 5.0 V

ts

Select Setup Time

45

ns

VCC = 5.0 V

th

Hold Time, Any Input

0

ns

DEFINITIONS OF TERMS

SETUP TIME(ts) — is defined as the minimum time required

for the correct logic level to be present at the logic input prior to

the clock transition from LOW-to-HIGH in order to be recog-

nized and transferred to the outputs.

HOLD TIME(th) — is defined as the minimum time following

the clock transition from LOW-to-HIGH that the logic level

must be maintained at the input in order to ensure continued

recognition. A negative Hold Time indicates that the correct

logic level may be released prior to the clock transition from

LOW-to-HIGH and still be recognized.

1.3 V

1.3 V

AC WAVEFORMS

Figure 1

Figure 2

Figure 3

*The shaded areas indicate when the input is permitted to change for predictable output performance.

I0 I1 *

1.3 V

1.3 V

1.3 V

1.3 V

1.3 V

1.3 V

1.3 V

1.3 V

1.3 V

1.3 V

1.3 V

1.3 V

1.3 V

1.3 V

1.3 V

1.3 V

Q

Q

CP

CP

CP

Q or Q

Q = I0

Q = I1

ts(L)

th(L)

tPHL

tPLH

th(H)

ts(L)

ts(H)

th(L) = 0

th(H) = 0

tPHL

tPLH

tPLH

Q

tPHL

tW(H)

ts(H)

tW(L)

S*

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