Datasheet

74VHC_VHCT244_1 © NXP B.V. 2009. All rights reserved.
Product data sheet Rev. 01 — 17 August 2009 8 of 16
NXP Semiconductors
74VHC244; 74VHCT244
Octal buffer/line driver; 3-state
[1] Typical values are measured at nominal supply voltage (V
CC
= 3.3 V and V
CC
= 5.0 V).
[2] t
pd
is the same as t
PLH
and t
PHL
.
t
en
is the same as t
PZL
and t
PZH
.
t
dis
is the same as t
PLZ
and t
PHZ
.
[3] C
PD
is used to determine the dynamic power dissipation P
D
(µW).
P
D
=C
PD
× V
CC
2
× f
i
+ ∑ (C
L
× V
CC
2
× f
o
) where:
f
i
= input frequency in MHz;
f
o
= output frequency in MHz;
C
L
= output load capacitance in pF;
V
CC
= supply voltage in Volts.
11. Waveforms
For type 74VHCT244
t
pd
propagation
delay
nAn to nYn; see Figure 6
[2]
V
CC
= 4.5 V to 5.5 V
C
L
= 15 pF - 3.5 7.4 1.0 8.5 1.0 9.5 ns
C
L
= 50 pF - 5.0 8.4 1.0 9.5 1.0 10.5 ns
t
en
enable time nOE to nYn; see Figure 7
V
CC
= 4.5 V to 5.5 V
C
L
= 15 pF - 3.5 10.4 1.0 12.0 1.0 13.0 ns
C
L
= 50 pF - 5.5 11.4 1.0 13.0 1.0 14.5 ns
t
dis
disable time nOE to nYn; see Figure 7
[2]
V
CC
= 4.5 V to 5.5 V
C
L
= 15 pF - 5.0 9.4 1.0 10.0 1.0 12.0 ns
C
L
= 50 pF - 7.0 11.4 1.0 13.0 1.0 14.5 ns
C
PD
power
dissipation
capacitance
per buffer;
C
L
=50pF;f=1 MHz;
V
I
= GND to V
CC
[3]
-12- - - - -pF
Table 7. Dynamic characteristics
…continued
GND = 0 V. For test circuit see Figure 8.
Symbol Parameter Conditions 25 °C −40 °C to +85 °C −40 °C to +125 °C Unit
Min Typ
[1]
Max Min Max Min Max
Measurement points are given in Table 8.
V
OL
and V
OH
are typical voltage output levels that occur with the output load.
Fig 6. Propagation delay input (nAn) to output (nYn)
mna171
nAn input
nYn output
t
PLH
t
PHL
GND
V
I
V
M
V
M
V
M
V
M
V
OH
V
OL