ST M74HCT138 User Manual
M74HCT138
3 TO 8 LINE DECODER (INVERTING)
■ HIGH SPEED:
t
= 16ns (TYP.) at VCC = 4.5V
PD
■ LOW POWER DISSIPATION:
= 4µA(MAX.) at TA=25°C
I
CC
■ COMPA TIBLE WITH TTL OUTPUTS :
V
= 2V (MIN.) VIL = 0.8V (MAX)
IH
■ SYMMETRICAL OUTPUT IMPEDANCE:
|I
| = IOL = 4mA (MIN)
OH
■ BALANCED PROPAGATION DELAYS:
t
≅ t
PHL
PLH
■ PIN AND FUNCTION COMPATIBLE WITH
74 SERIES 138
DESCRIPTION
The M74HCT138 is an high speed CMOS 3 TO 8
LINE DECODER fabricated with silicon gate
2
C
MOS technology.
If the device is enabled, 3 binary select inputs (A,
B, and C) determine which o ne of t he out puts will
go low. If enable input G1 is held low or either G2A
or G2B is held high, the decoding function is
inhibited and all the 8 outputs go high. Three
TSSOPDIP SOP
ORDER CODES
PACKAGE TUBE T & R
DIP M74HCT138B1R
SOP M74HCT138M1R M74HCT138RM13TR
TSSOP M74HCT138TTR
enable inputs are provided to ease cascade
connection and application of address decoders
for memory systems.
All inputs are equipped with protection circuits
against static discharge and transient excess
voltage.
PIN CONNECTION AND IEC LOGIC SYMBOLS
1/9August 2001
M74HCT138
INPUT AND OUTPUT EQUIVALENT CIRCUIT PIN DESCRIPTION
PIN No SYMBOL NAME AND FUNCTION
1, 2, 3 A, B, C Address Inputs
4, 5 G2A
6 G1 Enable Input
9, 10, 11, 12,
13, 14, 15,
7
8 GND Ground (0V)
16 V
TRUTH TABLE
, G2B Enable Inputs
to Y7 Data Outputs
Y0
CC
Positive Supply Voltage
INPUTS
ENABLE SELECT
G2B
X : Don’t Care
G2A G1CBAY0Y1 Y2 Y3 Y4 Y5 Y6 Y7
XXLXXXHHHHHHHH
XHXXXXHHHHHHHH
HXXXXXHHHHHHHH
LLHLLLLHHHHHHH
LLHLLHHLHHHHHH
LLHLHLHHLHHHHH
LLHLHHHHHLHHHH
LLHHLLHHHHLHHH
LLHHLHHHHHHLHH
LLHHHLHHHHHHLH
LLHHHHHHHHHHHL
OUTPUTS
LOGIC DIAGRAM
This log i c diagram has not be used to esti m ate propagation delays
2/9
M74HCT138
ABSOLUTE MAXIMUM RATINGS
Symbol Parameter Value Unit
V
V
V
I
I
OK
I
I
or I
CC
P
T
T
Absolute Maximum Ratings are those values beyond which damage to the device may occur. Functional operation under these conditions is
not implied
(*) 500mW at 65
RECOMMENDED OPERATING CONDITIONS
Symbol Parameter Value Unit
V
V
V
T
t
r
Supply Voltage
CC
DC Input Voltage -0.5 to VCC + 0.5
I
DC Output Voltage -0.5 to VCC + 0.5
O
DC Input Diode Current
IK
DC Output Diode Current
DC Output Current
O
DC VCC or Ground Current
GND
Power Dissipation
D
Storage Temperature
stg
Lead Temperature (10 sec)
L
°C; derate to 300mW by 10mW/°C from 65°C to 85°C
Supply Voltage
CC
Input Voltage 0 to V
I
Output Voltage 0 to V
O
Operating Temperature
op
, t
Input Rise and Fall Time (VCC = 4.5 to 5.5V)
f
-0.5 to +7 V
± 20 mA
± 20 mA
± 25 mA
± 50 mA
500(*) mW
-65 to +150 °C
300 °C
4.5 to 5.5 V
CC
CC
-55 to 125 °C
0 to 500 ns
V
V
V
V
DC SPECIFICATIONS
Symbol Parameter
V
V
V
V
I
∆ I
High Level Input
IH
Voltage
Low Level Input
IL
Voltage
High Level Output
OH
Voltage
Low Level Output
OL
Voltage
I
Input Leakage
I
Current
Quiescent Supply
CC
Current
Additional Worst
CC
Case Supply
Current
Test Condition Value
T
= 25°C
V
CC
(V)
A
Min. Typ. Max. Min. Max. Min. Max.
4.5
to
2.0 2.0 2.0 V
5.5
4.5
to
0.8 0.8 0.8 V
5.5
4.5
4.5
5.5
5.5
IO=-20 µA
I
=-4.0 mA
O
IO=20 µA
I
=4.0 mA
O
= VCC or GND
V
I
V
= VCC or GND
I
5.5 Per Input pin
= 0.5V or
V
I
V
= 2.4V
I
4.4 4.5 4.4 4.4
4.18 4.31 4.13 4.10
0.0 0.1 0.1 0.1
0.17 0.26 0.33 0.40
± 0.1 ± 1 ± 1 µA
2.0 2.9 3.0 mA
Other Inputs at
V
or GND
CC
I
= 0
O
-40 to 85°C -55 to 125°C
Unit
V
V
44080µA
3/9
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