L293D Dual H-Bridge Motor Driver IC Pins, Circuit, Working

Introduction: L293D Dual H-Bridge Motor Driver IC

L293D motor Driver IC is an integrated circuit that can drive two motors simultaneously and is usually used to control the motors in an autonomous system. This motor driver IC enables us to drive a DC motor in either direction and also control the speed of the motor.

L293D is a dual H-bridge motor driver IC. H-bridge is the simplest circuit for controlling a low current-rated motor. One H-bridge is capable to drive a DC motor bidirectional. L293D is a current enhancing IC. It can also act as a switching device.

The L293D is a 16-pin Integrated circuit, with eight pins, on each side, dedicated to the controlling of a motor. There are 2 input pins, 2 output pins and 1 enable pin for each motor. The L293D IC is designed to provide bidirectional drive currents of up to 600-mA at voltages from 4.5 V to 36 V. It is designed to drive inductive loads such as relays, solenoids, DC & bipolar stepping motors, as well as other high-current/high-voltage loads in positive-supply applications.

L293D motor Driver IC is one of the most popular drivers in the market. Because of several reasons such as cheap price (compared to other drivers), easy control, proper shape and size, no need for protective circuit and diodes, no need for heat sinks, and good resistance to temperature and high-speed variations, L293D motor driver is mostly preferred driver to the user.

Features and Characteristics of L293D IC

The followings are the main features and specifications of the L293D Motor Driver IC.

Wide supply voltage range: 4.5V to 36V
Output current 600mA per channel
Peak Output Current 1.2A per channel
High-Noise-Immunity Inputs
Separate Input-Logic Supply
Internal Electrostatic Discharge (ESD) Protection

L293D Pin Configuration & Description

The pin configuration diagram and real image of the L293D Motor Driver IC are shown below.

Pin 1 ( Enable1,2): When this pin is given High or Logic 1, the left part of the IC will work and when it is low, the left part doesn’t work. So, this pin is the Master Control pin for the left part of the IC
Pin 2 (Input 1): When this pin is High or Logic 1, output 1 becomes High. i.e. the current will flow through output 1
Pin 3 (Output 1): This pin is connected to one of the terminal of motor 1
Pin 4, Pin 5 ( GND): These pins should be connected to the circuit’s ground
Pin 6 (Output 2): This pin is connected to one of the terminal of motor 1
Pin 7 (Input 2): When this pin is given High or Logic 1, output 2 becomes high i.e. the current will flow through output 2
Pin 8 (VCC2): This is the voltage required to run the motor. It can be greater than IC voltage Vcc 1. If we are driving 12 V DC motors then make sure that this pin is supplied with 12 V
Pin 9 (Enable 3,4): When this pin is given High or logic 1, the right part of the IC will work, and when it is low the right part doesn’t work. So, this pin is the Master Control pin for the right part of the IC
Pin 10 (Input 3): When this pin is given High or Logic 1, output 3 becomes high i.e the current will flow through output 3
Pin 11 (Output 3): This pin is connected to one of the terminal of motor 2
Pin 12,13 (GND): These pins should be connected to the circuit’s ground
Pin 14 (Output 4): This pin is connected to one of the terminals of motor 2
Pin 15 (Input 4): When this pin is given High or Logical 1, output 4 becomes High i.e. the current will flow through output 4
Pin 16 (VCC1): This pin provides power to the IC. So, this pin should be supplied with a 5V

Notes: From the configuration of L293D Motor Driver IC, the following notes are pointed

Input 1, Input 2, Input 3, and Input 4 are input pins and act as direction control direction pins. Input 1, Input 2 pins control the spinning direction of motor 1 while Input 3, Input 4 control motor 2. If input logic at Input1, Input2 is (1,0) the motor rotates in one direction. And if input logic at Input1, Input2 is (0,1) the motor rotates in the other direction.
Enable1,2 and Enable3,4 have enabled pins and act as speed control pins. These are used to turn ON, OFF, and control the speed of motor1 and motor2 respectively. 5V DC is connected to these pins to operate the motor at its normal speed. For controlling the speed, PWM (Pulse Width Modulation) output can be given at these pins from the microcontroller.
There is a total of 4 ground pins in the L293D IC Motor Driver because it has to deal with heavy currents. Due to so much current flow in IC gets heated. So, we need a heat sink to reduce the heating and protect the IC from damage. IC may be heated during soldering the pins on PCB.

Refer to L293D Datasheets for more information.

Logical Diagram

The logic diagram of L293D IC which presents an internal logic followed by an IC is shown in the figure below.

Functional Block Diagram

A Functional diagram of a device shows the steps followed by that device in order to perform some action to give output. The functional block diagram for L293D IC is shown in the figure below.

Working Mechanism of L293D Motor Driver IC

The circuit diagram of the L293D Driver Motor IC designed for soldering on PCB with the connectors is shown in the figure below.

Here, four inputs such as Input 1, Input 2, Input 3, and Input 4 are given at input pins 2,7,10, and 14 respectively. Two Enables such as Enable 1,2 and Enable 3,4 are given at enabling pins 1 and 9 respectively. The connection of all pins of IC and other components is shown in the above circuit diagram.

Depending on the value of Inputs and Enables, the motor will rotate either in a clockwise direction or anticlockwise direction with full speed or less speed. The direction of rotation of the motor depends on the value of Inputs and the speed of rotation depends on the value of Enables. The motor is said to be in full speed when Enable is Hign and is said to be in less speed when Enable is provided with PWM.

Let us take Left Motor and assume the conditions when Enable is HIGH and Input 1 and Input 2 are HIGH and LOW respectively then the motor will move in a clockwise direction.

The behavior of the motor depending on the input conditions such as Inputs and Enables is shown in a tabular diagram as follows:
Here, Logical 1 is referred to as HIGH and Logical 0 is referred to as LOW.

Input 1	Input 2	Enable 1,2	Result
0	0	1	Stop
0	1	1	Anti-clockwise rotation
1	0	1	Clockwise rotation
1	1	1	Stop
0	1	50% duty cycle	Anti-clockwise rotation with half speed
1	0	50% duty cycle	Clockwise rotation with half speed