Datasheet
SN54HCT646, SN74HCT646
OCTAL BUS TRANSCEIVERS AND REGISTERS
WITH 3-STATE OUTPUTS
SCLS178C – MARCH 1984 – REVISED MARCH 2003
6
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
switching characteristics over recommended operating free-air temperature range, C
L
= 50 pF
(unless otherwise noted) (see Figure 2)
PARAMETER
FROM TO
V
CC
T
A
= 25°C SN54HCT646 SN74HCT646
UNIT
PARAMETER
(INPUT) (OUTPUT)
V
CC
MIN TYP MAX MIN MAX MIN MAX
UNIT
f
4.5 V 31 54 22 27
MHz
f
max
5.5 V 36 64 24 29
MHz
CLKBA or CLKAB
AorB
4.5 V 18 36 54 45
CLKBA
or
CLKAB
A
or
B
5.5 V 16 32 49 41
t
d
AorB
BorA
4.5 V 14 27 41 34
ns
t
pd
A
or
B
B
or
A
5.5 V 12 24 37 31
ns
SBA SAB
†
AorB
4.5 V 20 38 57 48
SBA
or
SAB
†
A
or
B
5.5 V 17 34 51 43
t
OE
AorB
4.5 V 25 49 74 61
ns
t
en
OE
A
or
B
5.5 V 22 44 67 55
ns
t
di
OE
AorB
4.5 V 25 49 74 61
ns
t
dis
OE
A
or
B
5.5 V 22 44 67 55
ns
t
DIR
AorB
4.5 V 25 49 74 61
ns
t
en
DIR
A
or
B
5.5 V 22 44 67 55
ns
t
di
DIR
AorB
4.5 V 25 49 74 61
ns
t
dis
DIR
A
or
B
5.5 V 22 44 67 55
ns
t
t
Any
4.5 V 9 12 18 15
ns
t
t
Any
5.5 V 7 11 16 14
ns
†
These parameters are measured with the internal output state of the storage register opposite that of the bus input.
switching characteristics over recommended operating free-air temperature range, C
L
= 150 pF
(unless otherwise noted) (see Figure 2)
PARAMETER
FROM TO
V
CC
T
A
= 25°C SN54HCT646 SN74HCT646
UNIT
PARAMETER
(INPUT) (OUTPUT)
V
CC
MIN TYP MAX MIN MAX MIN MAX
UNIT
CLKBA or CLKAB
AorB
4.5 V 24 53 80 66
CLKBA
or
CLKAB
A
or
B
5.5 V 22 47 52 60
t
d
AorB
BorA
4.5 V 22 44 67 55
ns
t
pd
A
or
B
B
or
A
5.5 V 20 39 60 50
ns
SBA SAB
†
AorB
4.5 V 26 55 83 69
SBA
or
SAB
†
A
or
B
5.5 V 24 49 74 62
OE
AorB
4.5 V 33 66 100 87
t
OE
A
or
B
5.5 V 22 59 90 74
ns
t
en
DIR
AorB
4.5 V 33 66 100 87
ns
DIR
A
or
B
5.5 V 22 59 90 74
t
t
Any
4.5 V 17 42 63 53
ns
t
t
Any
5.5 V 14 38 57 48
ns
†
These parameters are measured with the internal output state of the storage register opposite that of the bus input.
operating characteristics, T
A
= 25°C
PARAMETER TEST CONDITIONS TYP UNIT
C
pd
Power dissipation capacitance No load 50 pF
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