74LS251 Data Selector or Multiplexer IC With 3-State Output

The 74LS251 is an 8-input digital multiplexer with fast speed. These ICs have full on-chip binary decoding and a strobe-controlled three-state output for selecting one of eight data sources. To enable these devices, the strobe must be set to a low logic level. The three-state outputs allow several outputs to be connected to a single bus. TTL is always the output of the IC. As a result, it’s simple to interface with other TTL devices and microcontrollers. Thermal overload protection and ESD protection are among the many features included in the IC. The IC 74LS251 is smaller in size and has a much higher speed, making it suitable for use in a wide range of devices.

When the strobe input is HIGH, both outputs are in high-impedance mode, with both upper and lower transistors of each totem-pole output turned off, and the output does not significantly drive or load the bus. When the strobe remains LOW, the outputs activate and operate as standard TTL totem-pole outputs. To reduce the chances of two outputs attempting to take the same bus to opposite logic levels. As a result, the output control circuitry has a shorter average output disable time than an average output enable time.

A multiplexer/data selector is a digital combinational logic circuit that connects one or more input lines to a single output line. The select lines determine which inputs are connected to which outputs, as well as how much data can be sent over a network in a given amount of time. A data selector is another name for it.

Applications

• The 74LS251 IC used as a universal function generator to generate any logic function of  variables.
• Sometimes also used to encode the output of a flash analog to digital converter.