SDLS014 - DECEMBER 1972 - REVISED MARCH 1988
PRODUCTION DATA documents contain information current as of publicationdate. Products conform to specifications per the terms of Texas Instrumentsstandard warranty. Production processing does not necessarily include testingof all parameters.
These Schottky-clamped TTL MSI circuits are designed to be used in high-performancememory decoding or data-routing applications requiring very short propagationdelay times. In high-performance memory systems, these decoders can be usedto minimize the effects of system decoding. When employed with high-speedmemories utilizing a fast enable circuit, the delay times of these decodersand the enable time of the memory are usually less than the typical accesstime of the memory. This means that the effective system delay introducedby the Schottky-clamped system decoder is negligible.
The 'LS138, SN54S138, and SN74S138A decode one of eight lines dependenton the conditions at the three binary select inputs and the three enable inputs.Two active-low and one active-high enable inputs reduce the need for externalgates or inverters when expanding. A 24-line decoder can be implemented withoutexternal inverters and a 32-line decoder requires only one inverter. An enableinput can be used as a data input for demultiplexing applications.
All of these decoder/demultiplexers feature fully buffered inputs, eachof which represents only one normalized load to its driving circuit. All inputsare clamped with high-performance Schottky diodes to suppress line-ringingand to simplify system design.
The SN54LS138 and SN54S138 are characterized for operation over the fullmilitary temperature range of -55°C to 125°C. The SN74LS138 and SN74S138Aare characterized for operation from 0°C to 70°C.
View more information about generic part numbers:SN54LS138, SN54S138, SN74LS138, SN74S138A
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