Diodes 74AHCT138 User Manual
Description
The 74AHCT138 is an advanced high speed CMOS device that is
designed to be pin compatable with 74LS low power Schottky types.
The device accepts a three bit binary weighted address on input pins
A0, A1 and A2 and when enabled will produce one active low output
with the remaining seven being high.
There are two active LOW enable inputs E
HIGH enable input E3. The disabled device state results in all outputs
being high. The enable state occurs with E
E3 asserted high.
The multiple enable lines allow for the parallel expansion of decoders
to create 4-to-16 line versions with no additional parts and 5-to-32
versions with the addition of a single inverter.
1 and E2, and one active
1 and E2 asserted low and
74AHCT138
3 TO 8 LINE DECODER DEMULTIPLEXER
Pin Assignments
Features
Supply Voltage Range from 4.5V to 5.5V
Sinks or Sources 8mA at V
CMOS Low Power Consumption
Schmitt Trigger Action at All Inputs
Inputs Accept up to 6.0V
ESD Protection Tested per JESD 22
Exceeds 200-V Machine Model (A115-A)
Exceeds 2000-V Human Body Model (A114-A)
Exceeds 1000-V Charged Device Model (C101C)
Latch-Up Exceeds 250mA per JESD 78, Class II
Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2)
Halogen and Antimony Free. “Green” Device (Note 3)
Notes: 1. No purposely added lead. Fully EU Directive 2002/95/EC (RoHS) & 2011/65/EU (RoHS 2) compliant.
2. See http://www.diodes.com for more information about Diodes Incorporated’s definitions of Halogen- and Antimony-free, "Green" and Lead-free.
3. Halogen- and Antimony-free "Green” products are defined as those which contain <900ppm bromine, <900ppm chlorine (<1500ppm total Br + Cl) and
<1000ppm antimony compounds.
= 4.5V
CC
Click here for ordering information, located at the end of datasheet
Applications
Memory chip select decoding
Demultiplexing
Single line peripheral control
Allow simple serial bit streams from a microcontroller to control as
many peripheral lines as needed
74AHCT138
Document number: DS35483 Rev. 2 - 2
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74AHCT138
Pin Descriptions
Pin Number Pin Name Description
1 A0 Address Input 0
2 A1 Address Input 1
3 A2 Address Input 2
4
5
6 E3 Enable Input 3 (active HIGH)
7 Y7 Output 7 (active LOW)
8 GND Ground
9 Y6 Output 6 (active LOW)
10 Y5 Output 5 (active LOW)
11 Y4 Output 4 (active LOW)
12 Y3 Output 3 (active LOW)
13 Y2 Output 2 (active LOW)
14 Y1 Output 1 (active LOW)
15 Y0 Output o (active LOW)
16
1
E
2
E
V
CC
Enable Input 1 (active LOW)
Enable Input 2 (active LOW)
Supply Voltage
Function Table Diagram
Control Input Output
E1 E2
H X X X X X H H H H H H H H
X H X
X X L
L L H
74AHCT138
Document number: DS35483 Rev. 2 - 2
E3 A2 A1 A0
L L L H H H H H H H L
L L H H H H H H H L H
L H L H H H H H L H H
L H H H H H H L H H H
H L L H H H L H H H H
H L H H H L H H H H H
H H L H L H H H H H H
H H H L H H H H H H H
Y7 Y6 Y5 Y4 Y3 Y2 Y1 Y0
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Logic Diagram
74AHCT138
74AHCT138
Document number: DS35483 Rev. 2 - 2
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