DATA SHEET
Product specification
File under Integrated Circuits, IC06
December 1990
INTEGRATED CIRCUITS
74HC/HCT238
3-to-8 line decoder/demultiplexer
For a complete data sheet, please also download:
The IC06 74HC/HCT/HCU/HCMOS Logic Family Specifications
The IC06 74HC/HCT/HCU/HCMOS Logic Package Information
The IC06 74HC/HCT/HCU/HCMOS Logic Package Outlines
December 1990
2
Philips Semiconductors
Product specification
3-to-8 line decoder/demultiplexer
74HC/HCT238
FEATURES
Demultiplexing capability
Multiple input enable for easy expansion
Ideal for memory chip select decoding
Active HIGH mutually exclusive outputs
Output capability: standard
I
CC
category: MSI
GENERAL DESCRIPTION
The 74HC/HCT238 are high-speed Si-gate CMOS devices
and are pin compatible with low power Schottky TTL
(LSTTL). They are specified in compliance with JEDEC
standard no. 7A.
The 74HC/HCT238 decoders accept three binary
weighted address inputs (A
0
, A
1
, A
2
) and when enabled,
provide 8 mutually exclusive active HIGH outputs
(Y
0
to Y
7
).
The "238" features three enable inputs: two active LOW
(E
1
and E
2
) and one active HIGH (E
3
). Every output will be
LOW unless E
1
and E
2
are LOW and E
3
is HIGH.
This multiple enable function allows easy parallel
expansion of the "238" to a 1-of-32 (5 lines to 32 lines)
decoder with just four "238" ICs and one inverter.
The "238" can be used as an eight output demultiplexer by
using one of the active LOW enable inputs as the data
input and the remaining enable inputs as strobes. Unused
enable inputs must be permanently tied to their
appropriate active HIGH or LOW state.
The "238" is identical to the "138" but has non-inverting
outputs.
QUICK REFERENCE DATA
GND = 0 V; T
amb
= 25
C; t
r
= t
f
= 6 ns
Notes
1. C
PD
is used to determine the dynamic power dissipation (P
D
in
W):
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
V
CC
2
f
o
) = sum of outputs
C
L
= output load capacitance in pF
V
CC
= supply voltage in V
2. For HC the condition is V
I
= GND to V
CC
For HCT the condition is V
I
= GND to V
CC
-
1.5 V
ORDERING INFORMATION
See
"74HC/HCT/HCU/HCMOS Logic Package Information"
.
SYMBOL
PARAMETER
CONDITIONS
TYPICAL
UNIT
HC
HCT
t
PHL/
t
PLH
propagation delay
C
L
= 15 pF; V
CC
= 5 V
A
n
to Y
n
14
18
ns
E
3
to Y
n
16
20
ns
E
n
to Y
n
17
21
ns
C
I
input capacitance
3.5
3.5
pF
C
PD
power dissipation capacitance per package
notes 1 and 2
72
76
pF
December 1990
3
Philips Semiconductors
Product specification
3-to-8 line decoder/demultiplexer
74HC/HCT238
PIN DESCRIPTION
PIN NO.
SYMBOL
NAME AND FUNCTION
1, 2, 3
A
0
to A
2
address inputs
4, 5
E
1
, E
2
enable inputs (active LOW)
6
E
3
enable input (active HIGH)
8
GND
ground (0 V)
15, 14, 13, 12, 11, 10, 9, 7
Y
0
to Y
7
outputs (active HIGH)
16
V
CC
positive supply voltage
Fig.1 Pin configuration.
Fig.2 Logic symbol.
Fig.3 IEC logic symbol.
(a)
(b)
December 1990
4
Philips Semiconductors
Product specification
3-to-8 line decoder/demultiplexer
74HC/HCT238
Fig.4 Functional diagram.
Fig.5 Logic diagram.
FUNCTION TABLE
Note
1. H = HIGH voltage level
L = LOW voltage level
X = don't care
INPUTS
OUTPUTS
E
1
E
2
E
3
A
0
A
1
A
2
Y
0
Y
1
Y
2
Y
3
Y
4
Y
5
Y
6
Y
7
H
X
X
X
H
X
X
X
L
X
X
X
X
X
X
X
X
X
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
H
H
H
H
L
H
L
H
L
L
H
H
L
L
L
L
H
L
L
L
L
H
L
L
L
L
H
L
L
L
L
H
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
H
H
H
H
L
H
L
H
L
L
H
H
H
H
H
H
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
H
L
L
L
L
H
L
L
L
L
H
L
L
L
L
H
December 1990
5
Philips Semiconductors
Product specification
3-to-8 line decoder/demultiplexer
74HC/HCT238
DC CHARACTERISTICS FOR 74HC
For the DC characteristics see
"74HC/HCT/HCU/HCMOS Logic Family Specifications"
.
Output capability: standard
I
CC
category: MSI
AC CHARACTERISTICS FOR 74HC
GND = 0 V; t
r
= t
f
= 6 ns; C
L
= 50 pF
SYMBOL
PARAMETER
T
amb
(
C)
UNIT
TEST CONDITIONS
74HC
V
CC
(V)
WAVEFORMS
+
25
-
40 to
+
85
-
40 to
+
125
min.
typ.
max.
min.
max.
min.
max.
t
PHL
/ t
PLH
propagation delay
A
n
to Y
n
47
17
14
150
30
26
190
38
33
225
45
38
ns
2.0
4.5
6.0
Fig.6
t
PHL
/ t
PLH
propagation delay
E
3
to Y
n
52
19
15
160
32
27
200
40
34
240
48
41
ns
2.0
4.5
6.0
Fig.6
t
PHL
/ t
PLH
propagation delay
E
n
to Y
n
50
18
14
155
31
26
195
39
33
235
47
40
ns
2.0
4.5
6.0
Fig.7
t
THL
/ t
TLH
output transition time
19
7
6
75
15
13
95
19
16
110
22
19
ns
2.0
4.5
6.0
Figs 6 and 7
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