DM74S138

Supply Voltage . . . . . .  . . . . . .  . . . . . .  . . . . . .  . . . . . .  . . . . . .  . .. . . . 7V
Input Voltage  . . . . . .  . . . . . .  . . . . . .  . . . . . .  . . . . . .  . . . . . .  . .. . . 5.5V
Operating Free Air Temperature Range  . . . . . .  . . . . . . . . 0° C to +70°C
Storage Temperature Range  . . . . . .  . . . . . .  . . . . . . −65° C to +150° C

Note 1: The "Absolute Maximum Ratings" are those values beyond which the safety of the device cannot be guaranteed. The device should not be operated at these limits. The parametric values defined in the Electrical Characteristics tables are not guaranteed at the absolute maximum ratings. The "Recommended Operating Conditions" table will define the conditions for actual device operation.

These Schottky-clamped circuits DM74S138 are designed to be used in high-performance memory-decoding or data-routing applications, requiring very short propagation delay times. In high-performance memory systems these decoders can be used to minimize the effects of system decoding. When used with high-speed memories, the delay times of these DM74S138 decoders are usually less than the typical access time of the memory. This means that the effective system delay introduced by the decoder is negligible.

The DM74S138 decodes one-of-eight lines, based upon 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 external gates or inverters when expanding. A 24-line decoder can be implemented with no external inverters, and a 32-line decoder requires only one inverter. An enable input can be used as a data input for demultiplexing applications.

The DM74S139 comprises two separate two-line-to-fourline decoders in a single package. The active-LOW enable input can be used as a data line in demultiplexing applications.

All of these DM74S138 decoders/demultiplexers feature fully buffered inputs, presenting only one normalized load to its driving circuit. All inputs are clamped with high-performance Schottky diodes to suppress line-ringing and simplify system design.