74HC138D

The 74HC138 are high-speed Si-gate CMOS devices and are pin compatible with low power Scotty TTL (LSTTL). They are specified in compliance with JEDEC standard no. 7A. The 74HC138 decoders accept three binary weighted address inputs (A0, A1, A2) and when enabled, provide 8 mutually exclusive active LOW outputs (Y0 to Y7). The “138” features three enable inputs: two active LOW (E1 and E2) and one active HIGH (E3). Every output will be HIGH unless E1 and E2 are LOW and E3 is HIGH. This multiple enable function allows easy parallel expansion of the "138" to a 1-of-32 (5 lines to 32 lines) decoder with just four "138" ICs and one inverter. The ”138” can be used as an eight output demultiplexer by using one of the active LOW enable inputs as the data input and the remaining enable inputs as strobes. Unused enable inputs must be permanently tied to their appropriate active HIGH or LOW state. The ”138” is identical to the -238* but has inverting outputs.

Key features

• Demultiplexing capability
• Multiple input enable for easy expansion
• Ideal for memory chip select decoding
• Active LOW mutually exclusive outputs
• Output capability: standard
• ICC category: MSI