HIT HD74HCT238 Datasheet
HD74HCT238
3-to-8-line Decoder/Demultiplexer
Description
The HD74HCT238 has 3 binary select inputs (A, B, and C). If the device is enabled these inputs
determined which one of the eight normally high outputs will go low. Two active low and one active high
enables (G1, G2A and G2B) are provided to ease the cascading of decoders.
Features
• LSTTL Output Logic Level Compatibility as well as CMOS Output Compatibility
• High Speed Operation: tpd (A, B, C to Y) = 18.5 ns typ (CL = 50 pF)
• High Output Current: Fanout of 10 LSTTL Loads
• Wide Operating Voltage: VCC = 4.5 to 5.5 V
• Low Input Current: 1 µA max
• Low Quiescent Supply Current: ICC (static) = 4 µA max (Ta = 25°C)
HD74HCT238
Function Table
Inputs
Enable Select Outputs
G1G
XXHXXXLLLLLLLL
XHXXXXLLLLLLLL
LXXXXXLLLLLLLL
HLLLLLHLLLLLLL
HLLLLHLHLLLLLL
HLLLHLLLHLLLLL
HLLLHHLLLHLLLL
HLLHLLLLLLHLLL
HLLHLHLLLLLHLL
HLLHHLLLLLLLHL
HLLHHHLLLLLLLH
G
2A
CBAY0Y1Y2Y3Y4Y5Y6Y
2B
7
Pin Arrangement
Select
Inputs
Enable
Inputs
Outputs
G
G
G
Y
GND
A
2A
2B
1
2
B
3
C
4
5
6
1
7
7
A
B
C
G
2A
G
2B
G
1
Y
7
Y
0
Y
1
Y
2
Y
3
Y
4
Y
Y
5
6
8
16
15
14
13
12
11
10
V
CC
Y
0
Y
1
Y
2
Y
Outputs
3
Y
4
Y
5
Y
9
6
(Top view)
2
Logic Diagram
G
1
G
2B
G
2A
A
HD74HCT238
Y
0
Y
1
Y
2
Y
3
B
C
DC Characteristics
Ta = –40 to
Ta = 25°C
Item Symbol Min Typ Max Min Max Unit V
Input voltage V
Output voltage V
IH
V
IL
OH
2.0 — — 2.0 — V 4.5 to
— — 0.8 — 0.8 V 4.5 to
4.4 — — 4.4 — V 4.5 Vin = VIH or VILIOH = –20 µA
4.18 — — 4.13 — 4.5 IOH = –4 mA
V
OL
— — 0.1 — 0.1 V 4.5 Vin = VIH or VILIOL = 20 µA
— — 0.26 — 0.33 4.5 IOL = 4 mA
Input current Iin — — ±0.1 — ±1.0 µA 5.5 Vin = VCC or GND
Quiescent supply
I
CC
— — 4.0 — 40 µA 5.5 Vin = VCC or GND, Iout = 0 µA
current
+85°C Test Conditions
(V)
CC
5.5
5.5
Y
4
Y
5
Y
6
Y
7
3
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