04-07-2012, 03:12 PM
1-of-8 Decoder/ Demultiplexer
1-of-8 Decoder.pdf (Size: 130.26 KB / Downloads: 30)
The LSTTL/MSI SN74LS138 is a high speed 1-of-8 Decoder/
Demultiplexer. This device is ideally suited for high speed bipolar
memory chip select address decoding. The multiple input enables
allow parallel expansion to a 1-of-24 decoder using just three LS138
devices or to a 1-of-32 decoder using four LS138s and one inverter.
The LS138 is fabricated with the Schottky barrier diode process for
high speed and is completely compatible with all ON Semiconductor
TTL families.
• Demultiplexing Capability
• Multiple Input Enable for Easy Expansion
• Typical Power Dissipation of 32 mW
• Active Low Mutually Exclusive Outputs
• Input Clamp Diodes Limit High Speed Termination Effects
FUNCTIONAL DESCRIPTION
The LS138 is a high speed 1-of-8 Decoder/Demultiplexer
fabricated with the low power Schottky barrier diode
process. The decoder accepts three binary weighted inputs
(A0, A1, A2) and when enabled provides eight mutually
exclusive active LOW Outputs (O0–O7). The LS138
features three Enable inputs, two active LOW (E1, E2) and
one active HIGH (E3). All outputs will be HIGH unless E1
and E2 are LOW and E3 is HIGH.