This decoder utilizes advanced silicon-gate CMOS technol-
ogy, and is well suited to memory address decoding or data
routing applications. The circuit features high noise immuni-
ty and low power consumption usually associated with
CMOS circuitry, yet has speeds comparable to low power
Schottky TTL logic.
The MM54HC138/MM74HC138 has 3 binary select inputs
(A, B, and C). If the device is enabled these inputs deter-
mine 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.
The decoder's outputs can drive 10 low power Schottky TTL
equivalent loads, and are functionally and pin equivalent to
the 54LS138/74LS138. All inputs are protected from dam-
age due to static discharge by diodes to VCC and ground.
• Typical propagation delay: 20 ns
• Wide power supply range: 2V±6V
• Low quiescent current: 80 mA maximum (74HC Series)
• Low input current: 1 mA maximum
• Fanout of 10 LS-TTL loads
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