What is 74HC157 Multiplexer : Pin Configuration & Its Working

A mux or multiplexer is one kind of digital switch that includes 2M data inputs & a single output where ‘M’ is control inputs. So the data can be transmitted from inputs to output. Generally, the multiplexer is used in many communication systems. There are different types of mux ICs like 74×352, 74×151, 74×150, 74x151A & 74HC157 Multiplexer


In many digital systems, different digital circuits are used to implement a specific logic verified through their Boolean Expression but a multiplexer is a usual digital logic circuit in their exclusive design. This article discusses an overview of a 74HC157 Multiplexer and its working.

What is 74HC157 Multiplexer?

74HC157 multiplexer is a high-speed IC or integrated circuit that includes four 2-inputs based digital multiplexers. This IC uses an advanced Si gate CMOS technology and is well-matched through less power Schottky TTL.

74HC157 multiplexer includes two inputs like enable & select input and also two groups of registers. The select input will decide the register from which the information arrives. Its function is identified on a range of temperature from-55 °C – 125 °C.

74HC157 Multiplexer IC
74HC157 Multiplexer IC

It controls the maximum noise immunity & less power utilization of typical CMOS ICs & the capacity to control 10 LS-TTL loads.

This IC includes 4 two i/p digital multiplexers along with common select & STROBE inputs. Once the STROBE pin is at a low state, and then the 4 outputs will imagine the values preferred from the inputs. Similarly, once the STROBE input is at a high state, the 4 outputs will imagine like logical “0”.

A logic family-like 74HC is compatible with the average 74LS logic family. All inputs of this IC are defended from injury because of fixed discharge through inside diode clamps toward VCC & GND.

Pin Configuration/Pin Diagram

The pin configuration of 74HC157 Multiplexer is shown below. This IC includes 16-pins where each pin with its functionality is discussed below.

74HC157 Pin Configuration
74HC157 Pin Configuration

Pin1 (SELECT)

Pin1 is an enable select pin that is mainly used to choose the input lines from which the information is accessible at the outputs.


Pins 2, 5, 11 & 14 (PinA)

These four pins are the first i/p line of the four 2:1 multiplexers.

Pins 3, 6, 10 & 13 (PinB)

These four pins are the second i/p line of the four 2:1 multiplexers.

Pins 4, 7, 9 & 12 (Output Y)

These are the four output pins of the IC.

Pin8 (GND)

This pin is directly connected to the GND terminal of the circuit.

Pin15 (STROBE)

This is an active-low pin & is accountable for allowing or immobilized outputs.

Pin16 (Vcc)

This pin provides the power to the IC like +5V.

Features & Specifications

The features and specifications of a 74HC157 multiplexer include the following.

  • High noise immunity
  • It selects 4-bits of data using two sources under a common data select input control.
  • The enable (E) input pin is active LOW. Once enable pin (E) is HIGH, then outputs are LOW apart from all other input states.
  • Package Type is DIP
  • Voltage rating ranges from 2V to 6V
  • The current rating is less like 1µA
  • Rating of Temperature ranges from -55 to 125 o C
  • Number of Pins-16
  • Outputs will be displayed in the form of non-inverted.
  • It includes buffered i/ps & o/ps
  • The range of input voltage is 1.35V – 3.15V.
  • The o/ps are interfaced directly to NMOS, CMOS &TTL.
  • The driving capacity is 10 LS-TTL loads.
  • It is well-matched through the Input Logic of TTL/CMOS.
  • The propagation delay max Vcc = 4.5V at 25ns
  • Noise Immunity: NIL = 30%, NIH = 30% of VCC at VCC = 5V

Alternative 74HC157 multiplexers are CD4052, 74LV4053, SN74LS153, MPC507AU & CD4053

Where to use/Applications

The applications of a 74HC157 multiplexer include the following.

A digital device like a multiplexer includes a minimum of two or above inputs & single output.

A select pin in the multiplexer chooses the input that must appear on the o/p pin. This pin size mainly depends on the size of the multiplexer. This IC includes quad 2×1 multiplexers in a single IC, so it is also called a quad multiplexer chip. So, for a mux with 2×1 size, a single bit select line is sufficient as it chooses from two inputs simply.

Even though it includes 4 mux, however, we cannot manage every multiplexer separately because a common select line is used to control all multiplexers. So, if you are seeking above one 2×1 multiplexer in a chip & want to control every multiplexer through a single select line, this is the top choice for you.

74HC157 multiplexer IC is mainly used for multiplexing the data otherwise in communication lines. This IC includes 4 multiplexers with two input pins which can be used in ALU’s of computer memory and it can also be utilized to execute Boolean functions.

  • Memory of Computer
  • Communication Systems
  • ALUs (Arithmetic Logic Units)
  • Telephone Line Selector
  • Network Lines

How to use the 74HC157 Multiplexer

The 74HC157 IC multiplexer using in different applications is straightforward. This IC includes 2V to 6V of operating voltage but the typical voltage used by this circuit is 5V. The supply is given to the circuit can be done through the Vcc & GND pins.

To operate the circuit, enable pin should be connected to the GND terminal, so we can permanently ground it otherwise connected to MPU or MCU to control the multiplexer based on the requirement.
In this IC, there are 2:1 multiplexers – 4, for ease let us consider we are using simply one of the accessible 4 multiplexers.

74HC157 Multiplexer circuit
74HC157 Multiplexer circuit

When the multiplexer used is a 2:1 then it uses two inputs, which are connected to the Input A pin & the Input B pin then the multiplexer o/p can be obtained from the Y o/p pin.

Here, pin1 which is called the select line will decide which of the 2- inputs must be connected to the o/p pin. If pin1 is logic 0, then Input A will be reproduced on the o/p. Similarly, if this pin is logic 1 then the Input B will be reproduced on the Y o/p pin. The 74HC157 IC working is discussed below.

We can notice the 4 multiplexers where simply the 1st multiplexer is used for display purposes. The Enable pin in the IC can be grounded & the select line pin (A’/B) is controlled through a logic condition. Once the select pin is low, the o/p line can be connected to input A.

When the select line is high then the o/p pin will be connected to Input B. So, the truth table in the following will show all the achievable inputs & outputs combinations.

Enable Select I/P Data Inputs Data Inputs Output (157) Output (158)

E’

S I0 I1 Y Y’

H

X X X L H

L

L L X

L

H

L L

H

X

H L
L H X

L

L

H

L

H X

H

H

L

In the above tabular form, ‘H’ is high voltage level, ‘L’ is low voltage level & ‘X’ is don’t care.

Thus, this is all about an overview of the 74HC157 multiplexer datasheet. A multiplexer circuit is used to choose & route any one of the numerous input signals to an only output. A single-pole multi-position switch is the best example of a non-electronic circuit. These switches are extensively used in different electronic circuits. Multiplexer handles two kinds of data like analog & digital. For analog applications, multiplexers are built using relays and transistor switches. For digital application, they are built from standard logic gates.

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