The NXP 74HC251 is a high-speed Si-gate CMOS device and is pin compatible with Low-power Schottky TTL (LSTTL). It is specified in compliance with JEDEC standard no. 7A. The 74HC251 is an 8-input multiplexer with three-state outputs that can be used to multiplex eight separate input lines to one common output line. The selection of the input line is controlled by three select inputs (S0, S1, S2).

This versatile multiplexer features an input-enable pin which, when held at a high logic level, disables all inputs, causing the output to assume a high-impedance state. This high-impedance state is crucial for applications where multiple 74HC251 devices are connected to a common bus, allowing for data lines to be tri-stated and thus preventing bus contention.

The device's low power consumption makes it an ideal choice for battery-operated and low-power systems. Additionally, the 74HC251 has a wide operating voltage range from 2V to 6V, which provides a great deal of flexibility in terms of compatibility with other logic families and the ability to operate in various power environments.

Key features of the NXP 74HC251 include:

• 3-state outputs for bus-oriented applications
• 8-input multiplexer with binary address decoding
• Low power dissipation: ICC = 4 μA (max.) at TA = 25°C
• High noise immunity: VNIH = VNIL = 28% VCC (min.)
• Output capability: bus driver
• Wide operating voltage range: 2V to 6V
• Symmetrical output impedance: |IOH| = IOL = 4 mA (min.)
• Balance propagation delays: tPLH ≈ tPHL
• ESD protection: HBM JESD22-A114E exceeds 2000 V, MM JESD22-A115-A exceeds 200 V

With its robust design and high degree of functionality, the NXP 74HC251 is well-suited for a wide range of applications including data routing, signal gating, and multiplexing in computer and telecommunications systems. Whether for design prototyping or mass production, the 74HC251 is a reliable and versatile component that enhances the efficiency of digital systems.