54LS257A中文资料TRI-STATE® Quad 2-Data Selectors/Multiplexers数据手册TI规格书

描述 Description

General Description
These Schottky-clamped high-performance multiplexers feature TRI-STATE outputs that can interface directly with data lines of bus-organized systems. With all but one of the common outputs disabled (at a high impedance state), the low impedance of the single enabled output will drive the bus line to a high or low logic level. To minimize the possibility that two outputs will attempt to take a common bus to opposite logic levels, the output enable circuitry is designed such that the output disable times are shorter than the output enable times.
This TRI-STATE output feature means that n-bit (paralleled) data selectors with up to 258 sources can be implemented for data buses. It also permits the use of standard TTL registers for data retention throughout the system.

特性 Features

● TRI-STATE versions LS157 and LS158 with same pin
   outs
● Schottky-clamped for significant improvement in A-C
   performance
● Provides bus interface from multiple sources in high
   performance systems
● Average propagation delay from data input 12 ns
● Typical power dissipation
   LS257B 50 mW
   LS258B 35 mW
● Alternate military/aerospace devices (54LS257A/
   54LS258A) are available. Contact a National Semicon
   ductor Sales Office/Distributor for specifications.