MSP430 and DRV8830 Motor Driver

THE MSP430FR2433 LAUNCHPAD AND THE DRV8830

The DRV8830 contains N-channel and P-channel power MOSFET’s configured as an H-bridge and can drive one DC motor or one winding of a stepper motor as well as other loads like solenoids. The output driver can supply up to one amp DC and can operate with supply voltages from 2.75 to 6.8 volts. The internal PWM frequency is 44.5 kHz.

VOLTAGE REGULATION

The DRV8830 uses pulse width modulation (PWM) to maintain a constant motor speed and to compensate for changes in battery supply voltage. The voltage output is programmable via an I2C interface.

The voltage regulation circuit integrates the pulse width modulated output to obtain an average DC voltage value. This filtered PWM output is divided by four and compared to the output of the voltage setting (VSET DAC). If the averaged PWM output is lower than the output voltage setting (VSET DAC), the duty cycle of the PWM output is increased. If the averaged PWM output is higher than the output voltage setting (VSET DAC), the duty cycle of the PWM output is decreased. The voltage setting (VSET DAC) is programmed using the I2C serial interface.

If the programmed output voltage is greater than the supply voltage, the DRV8830 will operate at 100% duty cycle and the voltage regulator operation will be disabled. In this case, the device operates as a conventional “H” bridge.

CURRENT LIMIT

The DRV8830 contains a current sense circuit that uses an external resistor to set the maximum output current to the motor and to protect it in the event of a stalled condition.

The motor current is determined by monitoring the voltage across the external current limit resistor and comparing it to a reference voltage of 200mV. If the current limit voltage exceeds the reference voltage for more than about 3 uS, the PWM duty cycle will be reduced to limit the current to the value set by the sense resistor.

If the overcurrent condition persists, such as in a stalled motor condition, for more than approximately 275 mS, the “FAULTn” pin will be driven low and the “FAULT” and “ILIMIT” bit in the “FAULT” register will be set, and the motor driver will continue to operate.

Setting both bits “IN1” and “IN2” in the “CONTROL” register to either zero (standby/coast) or to one (brake) will clear the fault condition. Setting the “CLEAR” bit in the “FAULT” register or removing supply power to the DRV8830 will also clear the fault condition.

DRV8830 TERMINAL CONNECTIONS
NAMEPINI/ODESCRIPTION
GND5NAGROUND
VCC4NAPOWER SUPPLY
SDA9INPUT/OUTPUTI2C SERIAL DATA
SCL10INPUTI2C SERIAL CLOCK
A07INPUTADDRESS 1
A18INPUTADDRESS 2
FAULTn6OUTPUTFAULT OUTPUT
OUT13OUTPUTMOTOR BRIDGE OUT 1
OUT21OUTPUTMOTOR BRIDGE OUT 2
ISENSE2INPUT/OUTPUTCURRENT SENSE
PORT AND I2C eUSCI CONFIGURATION AND CONTROL

 

 

LINK: Additional Information on the DRV8830

 

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