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MM74HC251
AC Electrical Characteristics
V
CC
= 5V, T
A
= 25°C, C
L
= 15 pF, t
r
= t
f
= 6 ns
AC Electrical Characteristics
C
L
= 50 pF, t
r
= t
f
= 6 ns (unless otherwise specified)
Note 5: C
PD
determines the no load dynamic power consumption, P
D
= C
PD
V
CC
2
f + I
CC
V
CC
, and the no load dynamic current consumption,
I
S
= C
PD
V
CC
f + I
CC
.
Symbol Parameter Conditions Typ
Guaranteed
Units
Limit
t
PHL
, t
PLH
Maximum Propagation Delay 26 35 ns
A, B or C to Y
t
PHL
, t
PLH
Maximum Propagation 27 35 ns
Delay, A, B or C to W
t
PHL
, t
PLH
Maximum Propagation 22 29 ns
Delay, Any D to Y
t
PHL
, t
PLH
Maximum Propagation 24 32 ns
Delay, Any D to W
t
PZH
, t
PZL
Maximum Output Enable R
L
= 1 kΩ 19 27 ns
Time, W Output C
L
= 50 pF
t
PZH
, t
PZL
Maximum Output Enable R
L
= 1 kΩ 19 26 ns
Time, Y Output C
L
= 50 pF
t
PHZ
, t
PLZ
Maximum Output Disable Time R
L
= 1 kΩ 26 40 ns
W Output C
L
= 5 pF
t
PHZ
, t
PLZ
Maximum Output Disable Time R
L
= 1 kΩ 27 35 ns
Y Output C
L
= 5 pF
Symbol Parameter Conditions
V
CC
T
A
= 25°CT
A
= −40 to 85°CT
A
= −55 to 125°C
Units
Typ Guaranteed Limits
t
PHL
, t
PLH
Maximum Propagation Delay 2.0V 90 205 256 300 ns
A, B or C to Y 4.5V 31 41 51 60 ns
6.0V 26 35 44 51 ns
t
PHL
, t
PLH
Maximum Propagation 2.0V 95 205 256 300 ns
Delay, A, B or C to W 4.5V 32 41 51 60 ns
6.0V 27 35 44 51 ns
t
PHL
, t
PLH
Maximum Propagation 2.0V 70 195 244 283 ns
Delay, any D to Y 4.5V 27 39 49 57 ns
6.0V 23 33 41 48 ns
t
PHL
, t
PLH
Maximum Propagation 2.0V 75 185 231 268 ns
Delay, any D to W 4.5V 29 37 46 54 ns
6.0V 25 32 40 46 ns
t
PZH
, t
PZL
Maximum Output Enable Time R
L
= 1 kΩ 2.0V 45 150 188 218 ns
W Output 4.5V 21 30 38 44 ns
6.0V 18 26 33 38 ns
t
PZH
, t
PZL
Maximum Output Enable Time R
L
= 1 kΩ 2.0V 45 145 181 210 ns
Y Output 4.5V 21 29 36 42 ns
6.0V 18 25 31 36 ns
t
PHZ
, t
PLZ
Maximum Output Disable Time R
L
= 1 kΩ 2.0V 60 220 275 319 ns
W Output 4.5V 29 44 55 64 ns
6.0V 25 37 46 54 ns
t
PHZ
, t
PLZ
Maximum Output Disable Time R
L
= 1 kΩ 2.0V 60 195 244 283 ns
Y Output 4.5V 30 39 49 57 ns
6.0V 26 33 41 48 ns
t
THL
, t
TLH
Maximum Output Rise 2.0V 30 75 95 110 ns
and Fall Time 4.5V 8 15 19 22 ns
6.0V 7 13 16 19 ns
C
PD
Power Dissipation Capacitance (Note 5) (per package) 110 pF
C
IN
Maximum Input Capacitance 5 10 10 10 pF
