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1-of-8 Decoder/Demultiplexer
High-Performance Silicon-Gate CMOS
The SL74HC138 is identical in pinout to the LS/ALS138. The device
inputs are compatible with standard CMOS outputs; with pullup
resistors, they are compatible with LS/ALSTTL outputs.
The SL74HC138 decodes a three-bit Address to one-of-eight activelow outputs. This device features three Chip Select inputs, two activelow and one active-high to facilitate the demultiplexing, cascading, and
chip-selecting functions. The demultiplexing function is accomplished
by using the Address inputs to select the desired device output; one
of the Chip Selects is used as a data input while the other Chip Selects
are held in their active states.
• Outputs Directly Interface to CMOS, NMOS, and TTL
• Operating Voltage Range: 2.0 to 6.0 V
• Low Input Current: 1.0 µA
• High Noise Immunity Characteristic of CMOS Devices
SL74HC138
ORDERING INFORMATION
SL74HC138N Plastic
SL74HC138D SOIC
TA = -55° to 125° C for all packages
PIN ASSIGNMENT
LOGIC DIAGRAM
PIN 16 =VCC
PIN 8 = GND
FUNCTION TABLE
Inputs Outputs
CS1 CS2 CS3 A2 A1 A0 Y0 Y1 Y2 Y3 Y4 Y5 Y6 Y7
X X H
X H X
L X X
H L L
H L L
H L L
H L L
H L L
H L L
H L L
H L L
X X X
X X X
X X X
L L L
L L H
L H L
L H H
H L L
H L H
H H L
H H H
H H H H H H H H
H H H H H H H H
H H H H H H H H
L H H H H H H H
H L H H H H H H
H H L H H H H H
H H H L H H H H
H H H H L H H H
H H H H H L H H
H H H H H H L H
H H H H H H H L
SLS
H = high level (steady state)
L = low level (steady state)
X = don’t care
System Logic
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SL74HC138
MAXIMUM RATINGS*
Symbol Parameter Value Unit
VCC DC Supply Voltage (Referenced to GND) -0.5 to +7.0 V
VIN DC Input Voltage (Referenced to GND) -1.5 to VCC +1.5 V
V
DC Output Voltage (Referenced to GND) -0.5 to VCC +0.5 V
OUT
IIN DC Input Current, per Pin ±20 mA
I
DC Output Current, per Pin ±25 mA
OUT
ICC DC Supply Current, VCC and GND Pins ±50 mA
PD Power Dissipation in Still Air, Plastic DIP+
SOIC Package+
750
500
Tstg Storage Temperature -65 to +150 °C
TL Lead Temperature, 1 mm from Case for 10 Seconds
260 °C
(Plastic DIP or SOIC Package)
*
Maximum Ratings are those values beyond which damage to the device may occur.
Functional operation should be restricted to the Recommended Operating Conditions.
+Derating - Plastic DIP: - 10 mW/°C from 65° to 125°C
SOIC Package: : - 7 mW/°C from 65° to 125°C
RECOMMENDED OPERATING CONDITIONS
Symbol Parameter Min Max Unit
VCC DC Supply Voltage (Referenced to GND) 2.0 6.0 V
VIN, V
DC Input Voltage, Output Voltage (Referenced to GND) 0 VCC V
OUT
TA Operating Temperature, All Package Types -55 +125 °C
tr, tf Input Rise and Fall Time (Figure 2) VCC =2.0 V
VCC =4.5 V
V
=6.0 V
CC
0
0
0
1000
500
400
mW
ns
This device contains protection circuitry to guard against damage due to high static voltages or electric
fields. However, precautions must be taken to avoid applications of any voltage higher than maximum rated
voltages to this high-impedance circuit. For proper operation, VIN and V
GND≤(VIN or V
OUT
)≤VCC.
should be constrained to the range
OUT
Unused inputs must always be tied to an appropriate logic voltage level (e.g., either GND or VCC).
Unused outputs must be left open.
System Logic
SLS