STMicroelectronics M74HC138B1 - 3-to-8 Line Decoder/Demultiplexer

The M74HC138B1 is a high-speed CMOS 3-to-8 line decoder/demultiplexer fabricated by STMicroelectronics. This integrated circuit is designed to accept three binary weighted address inputs (A0, A1, and A2) and, when enabled, provide eight mutually exclusive active-LOW outputs (Y0 to Y7).

The device features three enable inputs: two active-LOW (E1 and E2) and one active-HIGH (E3). All outputs will be high unless E1 and E2 are LOW and E3 is HIGH. This multiple enable function allows easy parallel expansion of the device to a 1-of-32 (5 lines to 32 lines) decoder with just four M74HC138B1 devices and one inverter.

The M74HC138B1 operates from a wide range of power supply voltages, from 2V to 6V, making it suitable for battery-powered devices and other low-voltage applications. Its low quiescent current consumption ensures minimal battery drain when the device is not actively decoding.

Key features of the M74HC138B1 include:

• High-speed operation: t<sub>PD = 15 ns (typical) at V<sub>CC = 6V
• Low power dissipation: I<sub>CC = 4 µA (maximum) at T<sub>A = 25°C
• High noise immunity: V<sub>NIH and V<sub>NIL = 28% V<sub>CC (minimum)
• Output drive capability: 10 LSTTL loads
• Symmetrical output impedance: |I<sub>OH| = I<sub>OL = 4 mA (minimum)
• Pin and function compatible with 74 series 138

The M74HC138B1 is suitable for a wide range of applications, including:

• Memory decoding or data routing
• Control systems
• Computers
• Instrumentation
• Telecommunications systems

Available in a standard 16-pin plastic DIP package, the M74HC138B1 is also offered in other package options to suit diverse assembly requirements. This device is a logical choice for system designers who require a reliable and flexible decoder/demultiplexer for their complex digital systems.