Document
Preliminary
74AHC138
3-TO-8 LINE DECODER DEMULTIPLEXER
Description
Pin Assignments
The 74AHC138 is an advanced high speed CMOS device.
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 E1 and E2, and one active HIGH enable input E3. The disabled device state results in all outputs being high. The enable state occurs with E 1 and E 2 asserted low and 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.
Features
• Wide Supply Voltage Range from 2.0 V to 5.5 V • Sinks or sources 8mA at Vcc = 4.5V • CMOS low power consumption • Schmitt Trigger Action at All Inputs • Inputs accept up to 5.5 V • 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 • SO16 Available in “Green” Molding Compound (no Br, Sb)
• Lead-Free Finish; RoHS Compliant (Notes 1 & 2)
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.
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 < 1000 ppm antimony compounds.
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74AHC138
Document number: DS35482 Rev. 2 - 2
1 of 10 www.diodes.com
June 2013
© Diodes Incorporated
Preliminary
Pin Descriptions
Pin Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Pin Name A0 A1 A2 E1 E2 E3 Y7
GND Y6 Y5 Y4 Y3 Y2 Y1 Y0 Vcc
Description Address Input 0 Address Input 1 Address Input 2 Enable Input 1 (active LOW) Enable Input 2 (active LOW) Enable Input 3 (active HIGH) Output 7 (active LOW) Ground Output 6 (active LOW) Output 5 (active LOW) Output 4 (active LOW) Output 3 (active LOW) Output 2 (active LOW) Output 1 (active LOW) Output o (active LOW) Supply Voltage
74AHC138
Function Table Diagram
Control
Input
Output
E1
E2
E3
A2
A1
A0
Y7
Y6
Y5
Y4
Y3
Y2
Y1
Y0
H
X
X
X
X
X
H
H
H
H
H
H
H
H
X
H
X
X
X
L
L
L
H
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
74AHC138
Document number: DS35482 Rev. 2 - 2
2 of 10 www.diodes.com
June 2013
.