The MC54/74HC138A is identical in pinout to the LS138. The device inputs are compatible with standard CMOS outputs; with pullup resistors, they are compatible with LSTTL outputs. The HC138A decodes a three–bit Address to one–of–eight active–low outputs. This device features three Chip Select inputs, two active–low andone 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.

• Output Drive Capability: 10 LSTTL Loads
• 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
• In Compliance with the Requirements Defined by JEDEC Standard
No. 7A
• Chip Complexity: 100 FETs or 29 Equivalent Gates