Susie Maestre

user Electronics Engineer

city Innovuze Solutions Inc.

  • 4.5V to 36V Full-Bridge DC Motor Driver

  • Created: Feb 01, 2016

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A full-bridge DC motor driver configuration is an electronic circuit that enables a voltage across the motor in either direction. It allows DC motors to rotate forwards or backwards. This particular design is an evaluation kit for MAX14871 DC motor driver that provides a low-power and simple solution for driving and controlling brushed motors with voltages between 4.5V and 36V. It is designed to have a very low driver on resistance, which reduces power during dissipation. The MAX14871 includes 3 modes of current regulation: fast decay, slow decay, and 25% current ripple modes. The current regulation based on 25% ripple simplifies the design and enables regulation independent of motor characteristics. A separate voltage sense input (SNS) reduces current-sensing errors due to parasitic trace resistance.

This evaluation kit is used to demonstrate the functionality of MAX14871. In this design, the EN pin is set to active low to enable the driver outputs. The clockwise/forward direction is achieved when the PWM and DIR logic inputs are both ‘0’. The counter-clockwise/reverse direction is achieved when the PWM is logic 1, while the DIR is logic 0. The MAX15006 (U5) on-board LDO generates 3.3V for logic signals and for powering the fault LED. The 3.3V LDO also powers the on-board ICM7556 PWM signal generator. The ICM7556 (U2) and its external components connected are general-purpose timer circuit, which is available to generate PWM signals for switching either the PWM or DIR inputs. By adjusting the R1 potentiometer, the duty cycle of the output signal can be changed. The EV kit comes with the PWM frequency set up to 1kHz but can be adjusted up to 10kHz by changing the C3 capacitor. The J7 jumper can be used to set the MODE voltage high (3.3V) or low (0V). For 25% ripple mode, however, the MODE voltage must be between 0.5V and 1V. Apply an external voltage to the MODE test point, or connect a resistor divider on the R3 and R5 resistor pads to set the MODE voltage for this mode of operation.

This design features a simplified design such as charge-pump-less architecture, current regulation that only requires a sense resistor, internal/external VREF for current regulation, and fast/slow/25% ripple current regulation modes. This reference design is very useful in motor control applications. It is also ideal in industrial automation, printers, scanners, vending machines, and gaming machines.