Datasheet

74AHC_AHCT257_2 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 02 — 9 May 2008 11 of 16
NXP Semiconductors
74AHC257; 74AHCT257
Quad 2-input multiplexer; 3-state
Test data is given in Table 9.
Definitions test circuit:
R
T
= termination resistance should be equal to output impedance Z
o
of the pulse generator.
C
L
= load capacitance including jig and probe capacitance.
R
L
= load resistance.
S1 = test selection switch.
Fig 8. Test circuitry for measuring switching times
V
M
V
M
t
W
t
W
10 %
90 %
0 V
V
I
V
I
negative
pulse
positive
pulse
0 V
V
M
V
M
90 %
10 %
t
f
t
r
t
r
t
f
001aad983
DUT
V
CC
V
CC
V
I
V
O
R
T
R
L
S1
C
L
open
G
Table 9. Test data
Type Input Load S1 position
V
I
t
r
, t
f
C
L
R
L
t
PHL
, t
PLH
t
PZH
, t
PHZ
t
PZL
, t
PLZ
74AHC257 V
CC
≤ 3.0 ns 15 pF, 50 pF 1 kΩ open GND V
CC
74AHCT257 3.0 V ≤ 3.0 ns 15 pF, 50 pF 1 kΩ open GND V
CC