L298 - Control DC motor by L298 duel full-bridge chip

L298 is a Duel H-Bridge driver ic. It’s mean we can control two DC motors simultaneously or single stepper motor. Now we will discuss to control single DC motor with microcontroller PWM. Every H-Bridge can carry up to 2A current and up to 46V. So we will chose dc motor according to given specification.

Circuit Diagram & Pins Detail

L298 inputs accept standard TTL logic levels, you can connect both types 3.3v or 5v input in order to control L298. Four separate output bridges control with four separate input gates and two enable inputs are provided to enable or disable the device independently of the input signals.

SUGGESTIONS

A non inductive capacitor, usually of 100 nF, must be foreseen between both Vs and Vss, to ground, as near as possible to GND pin. When the large capacitor

of the power supply is too far from the IC, a second smaller one must be foreseen near the L298. The sense resistor, not of a wire wound type, must be grounded near the negative pole of Vs that must be near the GND pin of the I.C.

Each input must be connected to the source of the driving signals by means of a very short path. Turn-On and Turn-Off : Before to Turn-ON the Supply

Voltage and before to Turn it OFF, the Enable input must be driven to the Low state.

In the given schematic we connect two bridges parallel to get higher current output and D1 to D4 fast recovery diodes are place in reverse-bias orientation to reducing inductive kickback.

Sense Resistance

Sensing Resistance sense load current flow from the bridge and can be use to control the output current with external circuit to vary resistance value.  It can be calculate, for a example we are using 2A/24VDC motor and want to limit the maximum continues current to 2A and Vref is 1v.

Rsense  =  Vref / i

Rsense = 1 / 2

Rsense Power  =  Vref * i

Rsense Power = 1 * 2 = 2watt