74HC138

The 74HC138 from Hitachi is a high-speed CMOS decoder/driver integrated circuit. It is designed to accept a three-bit binary weighted address on input pins A0, A1, and A2. When enabled, it produces one active low output while the remaining seven outputs remain high.

This device features two active low enable inputs (E1, E2) and one active high enable input (E3). The disabled state results in all outputs being high. The enable state is achieved with E1 and E2 asserted low and E3 asserted high. The 74HC138 operates within a wide supply voltage range of 2.0V to 6.0V, offering CMOS low power dissipation and high noise immunity.

Key specifications include a typical propagation delay of 45 ns at nominal supply voltage and 225 ns overall. It has a load capacitance of 50 pF and operates across a temperature range of -40°C to +125°C. The component has a length of 5 mm and a peak reflow temperature of 260°C.

Applications for the 74HC138 include memory chip select decoding, demultiplexing, and single-line peripheral control, allowing simple serial bit streams from a microcontroller to control multiple peripheral lines.